An international review of the characteristics of viral nucleic acid-amplification testing (NAT) reveals a trend towards the use of smaller pool sizes and individual donation NAT.

BACKGROUND AND OBJECTIVES: Nucleic acid-amplification testing (NAT) is used for screening blood donations/donors for blood-borne viruses. We reviewed global viral NAT characteristics and NAT-yield confirmatory testing used by blood operators. MATERIALS AND METHODS: NAT characteristics and NAT-yield confirmatory testing used during 2019 was surveyed internationally by the International Society of Blood Transfusion Working Party Transfusion-Transmitted Infectious Diseases. Reported characteristics are presented herein. RESULTS: NAT was mainly performed under government mandate. Human immunodeficiency virus (HIV), hepatitis C virus (HCV) and hepatitis B virus (HBV) NAT was performed on all donors and donation types, while selective testing was reported for West Nile virus, hepatitis E virus (HEV), and Zika virus. Individual donation NAT was used for HIV, HCV and HBV by ~50% of responders, while HEV was screened in mini-pools by 83% of responders performing HEV NAT. Confirmatory testing for NAT-yield samples was generally performed by NAT on a sample from the same donation or by NAT and serology on samples from the same donation and a follow-up sample. CONCLUSION: In the last decade, there has been a trend towards use of smaller pool sizes or individual donation NAT. We captured characteristics of NAT internationally in 2019 and provide insights into confirmatory testing approaches used for NAT-yields, potentially benefitting blood operators seeking to implement NAT.

Coronary artery bypass grafting is associated with immunoparalysis of monocytes and dendritic cells.

Coronary artery bypass grafting (CABG) triggers a systemic inflammatory response that may contribute to adverse outcomes. Dendritic cells (DC) and monocytes are immunoregulatory cells potentially affected by CABG, contributing to an altered immune state. This study investigated changes in DC and monocyte responses in CABG patients at 5 time-points: admission, peri-operative, ICU, day 3 and day 5. Whole blood from 49 CABG patients was used in an ex vivo whole blood culture model to prospectively assess DC and monocyte responses. Lipopolysaccharide (LPS) was added in parallel to model responses to an infectious complication. Co-stimulatory and adhesion molecule expression and intracellular mediator production was measured by flow cytometry. CABG modulated monocyte and DC responses. In addition, DC and monocytes were immunoparalysed, evidenced by failure of co-stimulatory and adhesion molecules (eg HLA-DR), and intracellular mediators (eg IL-6) to respond to LPS stimulation. DC and monocyte modulation was associated with prolonged ICU length of stay and post-operative atrial fibrillation. DC and monocyte cytokine production did not recover by day 5 post-surgery. This study provides evidence that CABG modulates DC and monocyte responses. Using an ex vivo model to assess immune competency of CABG patients may help identify biomarkers to predict adverse outcomes.

Soluble mediators in packed red blood cells augment lipopolysaccharide-induced monocyte interleukin-1ß production.

BACKGROUND AND OBJECTIVES: Soluble mediators in packed red-blood-cell (PRBC) units have been hypothesized as a mechanism associated with transfusion-related immune modulation. Soluble mediators including damage-associated molecular patterns (DAMPs) are known to activate inflammasomes. Inflammasome complexes maturate caspase-1 and interleukin (IL)-1ß. We assessed whether PRBC supernatants (SN) modulated IL-1ß driven inflammation and whether macrophage migration inhibitory factor (MIF) was a contributing factor. MATERIALS AND METHODS: Isolated monocytes were incubated with PRBC-SN in an in vitro transfusion model. Lipopolysaccharide (LPS) was added in parallel to model a bacterial infection. Separately, recombinant MIF was used in the model to assess its role in IL-1ß driven inflammation. IL-1ß and caspase-1 were quantified in the PRBC-SN and culture SN from the in vitro model. RESULTS: PRBC-SN alone did not induce IL-1ß production from monocytes. However, PRBC-SN alone increased caspase-1 production. LPS alone induced both IL-1ß and caspase-1 production. PRBC-SN augmented LPS-driven IL-1ß and caspase-1 production. Recombinant MIF did not modulate IL-1ß production in our model. CONCLUSIONS: Soluble mediators in PRBC modulate monocyte IL-1ß inflammation, which may be a contributing factor to adverse effects of transfusion associated with poor patient outcomes. While MIF was present in PRBC-SN, we found no evidence that MIF was responsible for IL-1ß associated immune modulation.

Investigation of the variable In(Lu) phenotype caused by KLF1 variants.

INTRODUCTION: KLF1 is an essential transcriptional activator that drives erythropoiesis. KLF1 variants can result in the Inhibitor of Lutheran, or In(Lu), phenotype where red blood cells (RBCs) have reduced BCAM (LU) and CD44 (IN). Other RBC surface molecules also have changed expression; however, there is controversy in the literature regarding which are truly impacted. We aimed to investigate KLF1 variants in the Australian population. STUDY DESIGN AND METHODS: In(Lu) samples were sourced through screening and through the RBC reference laboratory. Blood donor samples (8036) were screened to identify weakened/absent Lub antigen. Samples were genotyped by massively parallel sequencing, while surface carbohydrates and blood group molecules were assessed by flow cytometry. Hemoglobin (Hb) types were analyzed by high-performance liquid chromatography. RESULTS: Four of 8036 donors were identified to be In(Lu), and two previously identified In(Lu) samples were provided from the RBC reference laboratory. Five different KLF1 variants were identified; two were novel: c.954G>C/p.Trp318Cys and c.421C>T/p.Arg141*. BCAM and CD44 were reduced in all samples, consistent with previous reports. As a group, In(Lu) RBCs had reduced CD35 (KN), ICAM4 (LW), and CD147 (OK), and demonstrated increased binding of lectins ECA and SNAI. One In(Lu) sample had elevated HbF and another elevated HbA2. CONCLUSION: Different KLF1 variants may potentially produce variable phenotypes. A framework for investigating KLF1 variants and their phenotypic impact has been provided. In the future, given available international databases, further testing algorithms (as advocated here) will allow for correlation of phenotype with genotype and therefore accurately document this variability between KLF1 variants.

Platelet concentrates modulate myeloid dendritic cell immune responses.

Platelet transfusion has been reported to modulate the recipients' immune system. To date, the precise mechanism(s) driving poor patient outcomes (e.g., increased rate of mortality, morbidity, infectious complications and prolonged hospital stays) following platelet transfusion are largely undefined. To determine the potential for platelet concentrates (PC) to modulate responses of crucial immune regulatory cells, a human in vitro whole blood model of transfusion was established. Maturation and activation of human myeloid dendritic cells (mDC) and the specialized subset blood DC antigen (BDCA)3+ DC were assessed following exposure to buffy-coat derived PC at day (D)2 (fresh) and D5 (date-of-expiry). In parallel, to model recipients with underlying viral or bacterial infection, polyinosinic:polycytidylic acid or lipopolysaccharide was added. Exposure to PC had less of an impact on mDC responses than BDCA3+ DC responses. PC alone downregulated BDCA3+ DC expression of co-stimulatory molecules CD40 and CD80. In the model of viral infection, PC downregulated expression of CD83, and in the bacterial model of infection, PC downregulated CD80, CD83, and CD86. PC alone suppressed mDC production of interleukin (IL)-8, IL-12 and tumor necrosis factor (TNF)-α and BDCA3+ DC production of IL-8, IL-12, and IL-6. In the model of viral infection, production of IL-12 and interferon-gamma inducible protein (IP)-10 was reduced in both DC subsets, and IL-8 was reduced in BDCA3+ DC following PC exposure. When modeling bacterial infection, PC suppressed mDC and BDCA3+ DC production of IL-6 and IL-10 with a reduction in TNF-α evident in mDC. This study assessed the impact of PC "transfusion" on DC surface antigen expression and inflammatory mediator production and provided the first evidence that PC transfusion modulates blood mDC and BDCA3+ DC maturation and activation, particularly in the models of infection. Results of this study suggest that patients who receive PC, particularly those with underlying infectious complications, may fail to establish an appropriate immune response precipitating poor patient outcomes.

Immunomodulatory effect of cryopreserved platelets: altered BDCA3+ dendritic cell maturation and activation in vitro.

BACKGROUND: Cryopreservation of platelets (PLTs) is useful in remote areas to overcome logistic problems associated with supply and can extend the shelf life to 2 years. During cryopreservation, properties of PLTs are modified. Whether changes in the cryopreserved PLT (CPP) product are associated with modulation of recipients' immune function is unknown. We aimed to characterize the immune profile of myeloid dendritic cells (mDCs) and the specialized blood DC antigen (BDCA)3+ subset after exposure to CPPs. STUDY DESIGN AND METHODS: Using an in vitro whole blood model of transfusion, the effect of CPPs on mDC and BDCA3+ DC surface antigen expression and inflammatory mediator production was examined using flow cytometry. In parallel, polyinosinic:polycytidylic acid (poly(I:C)) or lipopolysaccharide (LPS) was utilized to model processes activated in viral or bacterial infection, respectively. RESULTS: Cryopreserved PLTs had minimal impact on mDC responses but significantly modulated BDCA3+ DC responses in vitro. Exposure to CPPs alone up regulated BDCA3+ DC CD86 expression and suppressed interleukin (IL)-8, tumor necrosis factor (TNF)-α, and interferon-γ inducible protein (IP)-10 production. In both models of infection-related processes, exposure to CPPs down regulated BDCA3+ DC expression of CD40, CD80, and CD83 and suppressed BDCA3+ DC production of IL-8, IL-12, and TNF-α. CPPs suppressed CD86 expression in the presence of LPS and IP-10 and IL-6 production with poly(I:C). CONCLUSION: Cryopreserved PLTs may be immunosuppressive, and this effect is more evident when processes associated with infection are concurrently activated, especially for BDCA3+ DCs. This suggests that transfusion of CPPs in patients with infection may result in impaired BDCA3+ DC responses.

Pandemic H1N1 influenza A viruses are resistant to the antiviral activities of innate immune proteins of the collectin and pentraxin superfamilies.

Acquired immune responses elicited to recent strains of seasonal H1N1 influenza viruses provide limited protection against emerging A(H1N1) pandemic viruses. Accordingly, pre-existing or rapidly induced innate immune defenses are of critical importance in limiting early infection. Respiratory secretions contain proteins of the innate immune system, including members of the collectin and pentraxin superfamilies. These mediate potent antiviral activity and act as an initial barrier to influenza infection. In this study, we have examined the sensitivity of H1N1 viruses, including pandemic virus strains, for their sensitivity to collectins (surfactant protein [SP]-D and mannose-binding lectin [MBL]) and to the pentraxin PTX3. Human SP-D and MBL inhibited virus-induced hemagglutinating activity, blocked the enzymatic activity of the viral neuraminidase, and neutralized the ability of H1N1 viruses to infect human respiratory epithelial cells in a manner that correlated with the degree of glycosylation in the globular head of the hemagglutinin. Recent seasonal H1N1 viruses expressed three to four N-glycosylation sequons on the head of hemagglutinin and were very sensitive to inhibition by SP-D or MBL, whereas A(H1N1) pandemic viruses expressed a single N-glycosylation sequon and were resistant to either collectin. Of interest, both seasonal and pandemic H1N1 viruses were resistant to PTX3. Thus, unlike recent seasonal H1N1 strains of influenza virus, A(H1N1) pandemic viruses are resistant to the antiviral activities of innate immune proteins of the collectin superfamily.

Human neutrophil antigen 3 genotype impacts neutrophil-mediated endothelial cell cytotoxicity in a two-event model of TRALI.

BACKGROUND: Antibodies against human neutrophil antigen (HNA)-3a are associated with severe cases of transfusion-related acute lung injury (TRALI). The HNA-3 system is located on choline transporter-like 2 (CTL-2) protein. CTL-2 is encoded by the gene SLC44A2 and a single-nucleotide polymorphism c.461G>A results in two antigens: HNA-3a and HNA-3b. Three HNA-3 genotypes/ phenotypes exist: HNA-3aa, HNA-3bb, and HNA-3ab. Two different pathways of anti-HNA-3a TRALI have been described: a two-hit neutrophil-dependent pathway and a one-hit neutrophil-independent pathway. However, it is not clear whether HNA-3ab heterozygous patients have a lower risk of anti-HNA-3a-mediated TRALI compared to HNA-3aa homozygous patients. MATERIALS AND METHODS: Healthy volunteers were genotyped for HNA-3 by real-time polymerase chain reaction, and phenotyped for HNA-3a by granulocyte immunofluorescence test (GIFT) and granulocyte agglutination test (GAT) against two donor sera containing anti-HNA-3a antibodies. The two sera were also used in in vitro models of human pulmonary microvascular endothelial cell (HLMVEC) cytotoxicity to investigate pathways of TRALI development. RESULTS: For both anti-HNA-3a sera, GIFT results matched the genotype, with a lower GIFT ratio for HNA-3ab neutrophils compared to HNA-3aa neutrophils, whereas GAT results showed no difference in agglutination. HLMVEC cytotoxicity was not observed in a one-hit neutrophil-independent model but was observed in a two-hit neutrophil-dependent model. Differences in cytotoxicity were observed between the two anti-HNA-3a sera used. Consistent with reduced HNA-3a antigen density as measured by GIFT, HNA-3ab neutrophils mediated less HLMVEC cytotoxicity than HNA-3aa neutrophils. CONCLUSION: HNA-3 genotype and HNA-3a antigen expression impacted the severity of anti-HNA-3a-mediated HLMVEC cytotoxicity in a two-hit neutrophil-dependent model of TRALI. Different HNA-3a antibodies might also impact the magnitude of HLMVEC cytotoxicity.

Transfusion-related acute lung injury (TRALI): Potential pathways of development, strategies for prevention and treatment, and future research directions.

Transfusion-related acute lung injury (TRALI) can occur during or after a transfusion, and remains a leading cause of transfusion-associated morbidity and mortality. TRALI is caused by the transfusion of either anti-leukocyte antibodies or biological response modifiers (BRMs). Experimental evidence suggests at least six different pathways that antibody-mediated TRALI might follow: (i) two hit neutrophil activation; (ii) monocyte and neutrophil dependent; (iii) endothelial cell, neutrophil Fc receptor, platelet and neutrophil extracellular trap dependent; (iv) direct monocyte activation; (v) direct endothelial cell activation; and (vi) endothelial cell, complement and monocyte dependent. Two of these pathways (i and v) also apply to BRM-mediated TRALI. Different antibodies or BRMs might initiate different pathways. Even though six pathways are described, these might not be distinct, and might instead be interlinked or proceed concurrently. The different pathways converge upon reactive oxygen species release which damages pulmonary endothelium, precipitating fluid leakage and the clinical symptoms of TRALI. Additional pathways to the six described are likely to also contribute to TRALI pathogenesis, and this requires further investigation. This review also discusses evidence of protective mechanisms and their implications for clinical TRALI treatment. Finally, it suggests directions for future research to support the translation of these findings into strategies to prevent and treat clinical TRALI.

Mannose-binding lectin deficiency influences innate and antigen-presenting functions of blood myeloid dendritic cells.

Mannose-binding lectin (MBL) is a serum lectin that plays a significant role in innate host defence. Individuals with mutations in exon 1 of the MBL2 gene have reduced MBL ligand binding and complement activation function and increased incidence of infection. We proposed that, during infection, MBL deficiency may impact on dendritic cell (DC) function. We analysed the blood myeloid DC (MDC) surface phenotype, inflammatory cytokine production and antigen-presenting capacity in MBL-deficient (MBL-D) individuals and MBL-sufficient (MBL-S) individuals using whole blood culture supplemented with zymosan (Zy) or MBL-opsonized zymosan (MBL-Zy) as a model of infection. Zy-stimulated MDCs from MBL-D individuals had significantly increased production of interleukin (IL)-6 and tumour necrosis factor (TNF)-α. Stimulation with MBL-Zy significantly decreased IL-6 production by MDCs from MBL-D, but had no effect on TNF-α production. MDCs from both MBL-S and MBL-D individuals up-regulated expression of the activation molecule CD83, and down-regulated expression of homing (CXCR4), adhesion (CD62L, CD49d) and costimulatory (CD40, CD86) molecules in response to Zy and MBL-Zy. MDC from both MBL-D and MBL-S individuals induced proliferation of allogeneic (allo) T cells following Zy or MBL-Zy stimulation; however, MBL-D individuals demonstrated a reduced capacity to induce effector allo-T cells. These data indicate that MBL deficiency is associated with unique functional characteristics of pathogen-stimulated blood MDCs manifested by increased production of IL-6, combined with a poor capacity to induce effector allo-T-cell responses. In MBL-D individuals, these functional features of blood MDCs may influence their ability to mount an immune response.

Mannose-binding lectin as part of the complement pathway: characterization in non-inflamed and inflamed human eyes.

BACKGROUND: Mannose-binding lectin plays a central effector role in the lectin pathway of complement activation. Frequently occurring MBL2 polymorphisms result in mannose-binding lectin deficiency, which increases susceptibility to infection. We characterized mannose-binding lectin levels and function in non-inflamed and inflamed human eyes, and evaluated its relationship to blood mannose-binding lectin levels and function. DESIGN: Prospective, observational clinical study with controls and cases. PARTICIPANTS: Twenty-seven patients with paired blood and ocular samples (aqueous and/or vitreous) including 15 controls (non-inflamed) and 12 cases (inflamed). METHODS: Blood and ocular samples were collected from controls (n = 15) with quiet eyes during elective cataract surgery and cases with inflamed eyes including proven/suspected endophthalmitis (n = 11) and herpetic retinal vasculitis (n = 1). Mannan-binding and C4 deposition enzyme-linked quantify mannose-binding lectin levels and function. MAIN OUTCOME MEASURES: Blood and ocular mannose-binding lectin levels and function. RESULTS: Of 27 patients, 10 (37%) were mannose-binding lectin-deficient (defined as blood mannose-binding lectin levels <500 ng/mL). Blood mannose-binding lectin levels (P= 0.16) or function (P= 0.43) were not significantly different between controls and cases. As expected, there was a high correlation between blood mannose-binding lectin levels and function (r(2) = 0.74). However, there was significantly more mannose-binding lectin in inflamed eyes than non-inflamed eyes measured as level (P < 0.01) or C4 deposition function (P < 0.01). CONCLUSIONS: Our study demonstrated that mannose-binding lectin is significantly elevated in inflamed human eyes but virtually undetectable in non-inflamed control eyes, suggesting a role in sight-threatening ocular inflammation.

Therapeutic role for mannose-binding lectin in cigarette smoke-induced lung inflammation? Evidence from a murine model.

Defective efferocytosis in the airway may perpetuate inflammation in smokers with/without chronic obstructive pulmonary disease. Mannose-binding lectin (MBL) improves efferocytosis in vitro; however, the effects of in vivo administration are unknown. MBL circulates in complex with MBL-associated serine proteases (MASPs), and efferocytosis involves activation of cytoskeletal-remodeling molecules, including Rac1/2/3. We hypothesized that MBL would improve efferocytosis in vivo, and that possible mechanisms for this effect would include up-regulation of Rac1/2/3 or MASPs. We used a smoking mouse model to investigate the effects of MBL on efferocytosis. MBL (20 microg/20 g mouse) was administered via nebulizer to smoke-exposed mice. In lung tissue (disaggregated) and bronchoalveolar lavage (BAL), we investigated leukocyte counts, apoptosis, and the ability of alveolar and tissue macrophages to phagocytose apoptotic murine epithelial cells. In human studies, flow cytometry, ELISA, and RT-PCR were used to investigate the effects of MBL on efferocytosis, Rac1/2/3, and MASPs. Smoke-exposed mice showed significantly reduced efferocytosis in BAL and tissue. Efferocytosis was significantly improved by MBL (BAL: control, 26.2%; smoke-exposed, 17.66%; MBL + smoke-exposed, 27.8%; tissue: control, 35.9%; smoke-exposed, 21.6%; MBL + smoke-exposed, 34.5%). Leukocyte/macrophage counts were normalized in smoke-exposed mice treated with MBL. In human studies, MBL was reduced in chronic obstructive pulmonary disease and in smokers, and was significantly correlated with reduced efferocytosis ex vivo. MASPs were not detected in BAL, and were not produced by alveolar or tissue macrophages. MBL significantly increased macrophage expression of Rac1/2/3. We provide evidence for Rac1/2/3 involvement in the MBL-mediated improvement in efferocytosis, and a rationale for investigating MBL as a supplement to existing therapies in smoking-related lung inflammation.

Mannose-binding lectin status is associated with risk of major infection following myeloablative sibling allogeneic hematopoietic stem cell transplantation.

Mannose-binding lectin (MBL) is a mediator of innate immunity that influences the risk of infection in a range of clinical settings. We previously reported associations between MBL2 genotype and infection in a retrospective study of myeloablative allogeneic hematopoietic stem cell transplantation (allo-HCT). However, other studies have been inconclusive, and the role of MBL in reduced-intensity conditioning (RIC) transplantation is unknown. Here we report a prospective study examining MBL2 genotype, MBL levels, and risk of major infection following HLA-matched sibling myeloablative (n = 83) and RIC (n = 59) HCT. Baseline MBL levels were higher in recipients than donors (P < .001), and recipient MBL levels increased during the peritransplantation period (P = .001), most notably in MBL2 wild-type individuals receiving myeloablative total body irradiation (mTBI). MBL2 coding mutations were associated with major infection in recipients receiving mTBI. The cumulative incidence of major infection in recipient harboring an MBL2 mutation receiving mTBI was 70.6%, compared with 31.1% of those without mutations not receiving mTBI (P = .01). MBL status was not associated with infection in RIC transplants. These results confirm the association of MBL status with risk of infection in myeloablative, TBI-conditioned transplantation. Studies examining the role of MBL replacement therapy to prevent infection in this setting should be considered.

Inverse Relationship Between Lipopolysaccharide Concentration and Monocyte and Dendritic Cells Inflammatory Response.

Dendritic cells (DCs) and monocytes are key immunoregulatory cells that link the innate and adaptive immune response. However, understanding of human cell-specific responses to different doses of stimuli including lipopolysaccharide (LPS) is limited. This study investigated the monocyte and classical DC (cDC)-specific, as well as the overall inflammatory response after exposure to varying doses of LPS. Fresh peripheral whole blood (n = 8) was used in an in vitro peripheral blood culture model to assess cDC and monocyte responses in coculture with varying doses of LPS (0.25, 0.5, 0.75, 1 µg/mL). cDC and monocyte cytokine responses were measured through flow cytometry. Supernatants collected from the in vitro model were used in a cytometric bead array to assess the overall inflammatory response. Exposure to all doses of LPS tested increased monocyte, cDC, and the overall leukocyte response. A dose-dependent reduction in cDC and monocyte cytokine production was also evident with higher LPS doses. This study demonstrates that cell-subset-specific responses are more susceptible to LPS exposure compared with the overall inflammatory response. Therefore, assays that assess cell-specific immune responses may be more beneficial to identify underlying pathophysiology of infection and inflammation.

Donor mannose-binding lectin deficiency increases the likelihood of clinically significant infection after liver transplantation.

BACKGROUND: Mannose-binding lectin (MBL) is an important mediator of innate immunity and is synthesized primarily by the liver. Low MBL levels are common, are due primarily to polymorphisms in the gene encoding MBL (MBL2), and are associated with an increased risk of infection, particularly when immunity is compromised. We report a large, retrospective study that examined the association between MBL status and clinically significant infection following orthotopic liver transplantation. METHODS: One hundred two donor-recipient orthotopic liver transplantation pairs were studied. Five polymorphisms in the promoter and coding regions of MBL2 were examined. MBL levels were measured, using the mannan-binding and C4-deposition assays, in serum samples obtained before and after transplantation. Associations between MBL status, as assessed by serum MBL levels and MBL2 genotype, and time to first clinically significant infection (CSI) after transplantation were examined in survival analysis with consideration of competing risks. RESULTS: The median duration of follow-up after orthotopic liver transplantation was 4 years. Thirty-six percent of recipients developed CSI after transplantation. The presence of MBL2 coding mutations in the donor was significantly associated with CSI in the recipient; the cumulative incidence function of infection was 55% in recipients of deficient livers, compared with 32% for recipients of wild-type livers (P = .002). Infection was not associated with recipient MBL2 genotype. Low MBL levels after orthotopic liver transplantation levels (mannan-binding <1 microg/mL or C4 deposition <0.2 C4 U/microL) were also associated with CSI (cumulative incidence function, 52% vs. 20%, P = .003; and cumulative incidence function, 54% vs. 24%, P = .007, respectively). In multivariate analysis, mutation in the MBL2 coding region of the donor (hazard ratio, 2.8; P = .005) and the use of cytomegalovirus prophylaxis (hazard ratio, 2.6; P = .005) were independently associated with CSI. CONCLUSIONS: Recipients of MBL-deficient livers have almost a 3-fold greater likelihood of developing CSI and may benefit from MBL replacement.

Genetic Variants Within the Erythroid Transcription Factor, KLF1, and Reduction of the Expression of Lutheran and Other Blood Group Antigens: Review of the In(Lu) Phenotype.

Erythroid-specific Krüppel-like factor 1, or KLF1, is an integral transcriptional activator for erythropoiesis. Genetic variants within KLF1 can result in a range of erythropoietic clinical phenotypes from benign to significant. The In(Lu) phenotype refers to changes in the quantitative expression of blood group-associated red cell surface molecules due to KLF1 variants which are otherwise clinically benign. These clinically benign KLF1 variants are associated with a reduced expression of 1 or more red cell membrane proteins/carbohydrates that carry blood group antigens for the LU (Lutheran), IN (Indian), P1PK, LW (Landsteiner-Wiener), KN (Knops), OK, RAPH, and I blood group systems. This is of significance during routine serologic blood typing when expression falls below the test sensitivity and therefore impacts on the ability to accurately detect the presence of affected blood group antigens. This is of clinical importance because the transfusion requirements for individuals with the In(Lu) phenotype differ from those of individuals that have a true Lunull phenotype. With this review, we summarize the current body of knowledge with regard to the In(Lu) phenotype and associated KLF1 variants. Our review also highlights discordant reports and provides insights for future research and management strategies. Serological heterogeneity in blood group expression of In(Lu) individuals has been shown, but studies are limited by the low prevalence of the phenotype and therefore the small numbers of samples. They are further limited by availability and inconsistent application of serological reagents and varying test algorithms. With the advent of genome sequence-based testing, an increasing list of In(Lu)-associated KLF1 variants is being revealed. The spectrum of effects on blood group expression due to these variants warrants further attention, and a consistent methodological approach of studies in larger cohorts is required. We propose that a recently reported testing framework of standardized serological studies, flow cytometry, and variant analysis be adopted; and that the international databases be curated to document KLF1 variability and the resultant In(Lu) red cell blood group expression. This will provide better classification of KLF1 variants affecting blood group expression and allow for phenotype prediction from genotype, accurate typing of In(Lu) individuals, and better transfusion management of related challenging transfusion scenarios.

Low serum mannose-binding lectin level increases the risk of death due to pneumococcal infection.

BACKGROUND: Previous studies have shown associations between low mannose-binding lectin (MBL) level or variant MBL2 genotype and sepsis susceptibility. However, MBL deficiency has not been rigorously defined, and associations with sepsis outcomes have not been subjected to multivariable analysis. METHODS: We reanalyzed MBL results in a large cohort with use of individual data from 4 studies involving a total of 1642 healthy control subjects and systematically defined a reliable deficiency cutoff. Subsequently, data were reassessed to extend previous MBL and sepsis associations, with adjustment for known outcome predictors. We reanalyzed individual data from 675 patients from 5 adult studies and 1 pediatric study of MBL and severe bacterial infection. RESULTS: XA/O and O/O MBL2 genotypes had the lowest median MBL concentrations. Receiver operating characteristic analysis revealed that an MBL cutoff value of 0.5 microg/mL was a reliable predictor of low-producing MBL2 genotypes (sensitivity, 82%; specificity, 82%; negative predictive value, 98%). MBL deficiency was associated with increased likelihood of death among patients with severe bacterial infection (odds ratio, 2.11; 95% confidence interval, 1.30-3.43). In intensive care unit-based studies, there was a trend toward increased risk of death among MBL-deficient patients (odds ratio, 1.58; 95% confidence interval, 0.90-2.77) after adjustment for Acute Physiology and Chronic Health Enquiry II score. The risk of death was increased among MBL-deficient patients with Streptococcus pneumoniae infection (odds ratio, 5.62; 95% confidence interval, 1.27-24.92) after adjustment for bacteremia, comorbidities, and age. CONCLUSIONS: We defined a serum level for MBL deficiency that can be used with confidence in future studies of MBL disease associations. The risk of death was increased among MBL-deficient patients with severe pneumococcal infection, highlighting the pathogenic significance of this innate immune defence protein.

Packed Red Blood Cell Transfusion Modulates Myeloid Dendritic Cell Activation and Inflammatory Response In Vitro.

Transfusion of packed red blood cells (PRBCs) modulates patients' immune responses and clinical outcomes; however, the underpinning mechanism(s) remain unknown. The potential for PRBC to modulate myeloid dendritic cells (mDC) and blood DC antigen 3 was assessed using an in vitro transfusion model. In parallel, to model processes activated by viral or bacterial infection, toll-like receptor agonists polyinosinic:polycytidylic acid or lipopolysaccharide were added. Exposure to PRBC upregulated expression of CD83 and downregulated CD40 and CD80 on both DC subsets, and it suppressed production of interleukin (IL)-6, IL-8, IL-12, tumor necrosis factor-α, and interferon-gamma-inducible protein-10 by these cells. Similar effects were observed when modeling processes activated by concurrent infection. Furthermore, exposure to PRBC at date of expiry was associated with more pronounced effects in all assays. Our study suggests PRBC have an impact on recipient DC function, which may result in failure to establish an appropriate immune response, particularly in patients with underlying infection.

Donor white blood cell survival and cytokine profiles following red blood cell transfusion in Australian major trauma patients.

BACKGROUND: The potential for the co-existence of genetically disparate cells (microchimerism) and associated cytokine profiles following red blood cell (RBC) transfusion in trauma patients has not been well characterized to date. This study investigated the incidence of surviving donor white blood cells (known as transfused-associated microchimerism (TAM)) and cytokine changes following blood transfusion in trauma patients. STUDY DESIGN AND METHODS: Trauma patients with an injury severity score (ISS) >12 who had been transfused between 2012-2016 with at least 5 units of RBC units over a 4 h period were recruited. Trauma patients with ISS > 12 who did not require blood transfusion were recruited as controls. The incidence of TAM was determined using a panel of insertion/deletion (InDel) bi-allelic polymorphisms. Selected pro- and anti-inflammatory cytokine profiles were analyzed using cytometric bead array. RESULTS: The transfused cohort (n = 40) had median ISS of 28 [12-66], received a median of 11 RBC units [4-114] and had median hospital length of stay of 35 days [1-152]. Only 11 (27.5%) patients returned for follow-up blood sampling after discharge. Of these, one patient showed an InDel pattern indicating the presence of TAM. No patients in the control cohort (n = 49) showed TAM. Cytokines IL-10 and IL-6 were found to be elevated in the transfused trauma patients. CONCLUSION: In this cohort, TAM was found to occur in one patient of the 11 who received a blood transfusion. Elevated IL-6 and IL-10 cytokines were detected in those patients who were transfused. However, the incidence of TAM could not be correlated with the elevated cytokine profiles for this cohort.