C1q-binding DSA and allograft outcomes in pediatric kidney transplant recipients.

Donor-specific antibody (DSA) is an independent risk factor for antibody-mediated rejection (ABMR) and graft loss. The C1q assay differentiates complement from non-complement-binding DSA and C1q-binding DSA may lead to poor allograft survival. Our aim was to characterize the type of DSA seen in pediatric kidney transplant recipients and to determine whether complement binding DSA was associated with inferior graft survival.This was a single-center retrospective study of 48 children who were transplanted between 2009 and 2016. DSA were monitored using Luminex single antigen beads. A negative crossmatch was required to proceed with transplantation. The median follow-up time was 4.9 (3.4, 7.9) years. The median age was 12 (5.7, 15.4) years. DSA developed in 27/48 (56.3%), while C1q-binding DSA developed in 17/27 (63%). There were no significant differences between DSA negative, C1q-binding DSA, and C1q negative DSA, with regard to the number of HLA-ABDR (P  =  .09) or HLA-DQ mismatches alone (P  =  .16). For both C1q negative and C1q-binding DSA, DQ was the most common target of the DSA (19/27; 70.4%). C1q-binding DSA was associated with a significantly higher frequency of biopsy proven rejection (76.5%) when compared to C1q negative (10%) and DSA negative (14.3%); P  =  .001. Graft loss was seen in 6 (12.5%), all of whom had C1q-binding DSA (P  =  .004). C1q-binding DSA was most commonly directed to DQ antigens. C1q-binding DSA was associated with increased rejection and graft loss. Monitoring for C1q-binding DSA may risk stratify recipients and guide physician management.

COVID-19 infection in kidney transplant recipients at the epicenter of pandemics.

We investigated the prevalence and clinical outcomes of COVID-19 in recipients of kidney transplants in the Bronx, New York, one of the epicenters of the pandemic. Between March 16 and June 2, 2020, 132 kidney transplant recipients tested positive by SARS-CoV-2 RT-PCR. From May 3 to July 29, 2020, 912 kidney transplant recipients were screened for SARS-CoV-2 IgG antibodies during routine clinic visits, of which 16.6% tested positive. Fifty-five of the 152 patients had previously tested positive by RT-PCR, while the remaining 97 did not have significant symptoms and had not been previously tested by RT-PCR. The prevalence of SARS-CoV-2 infection was 23.4% in the 975 patients tested by either RT-PCR or SARS-CoV-2 IgG. Older patients and patients with higher serum creatinine levels were more likely diagnosed by RT-PCR compared to SARS-CoV-2 IgG. Sixty-nine RT-PCR positive patients were screened for SARS-CoV-2 IgG antibodies at a median of 44 days post-diagnosis (Inter Quartile Range 31-58) and 80% were positive. Overall mortality was 20.5% but significantly higher (37.8%) in the patients who required hospitalization. Twenty-three percent of the hospitalized patients required kidney replacement therapy and 6.3% lost their allografts. In multivariable analysis, older age, receipt of deceased-donor transplantation, lack of influenza vaccination in the previous year and higher serum interleukine-6 levels were associated with mortality. Thus, 42% of patients with a kidney transplant and with COVID-19 were diagnosed on antibody testing without significant clinical symptoms; 80% of patients with positive RT-PCR developed SARS-CoV-2 IgG and mortality was high among patients requiring hospitalization.

Tacrolimus variability is associated with de novo donor-specific antibody development in pediatric renal transplant recipients.

BACKGROUND: Donor-specific antibody (DSA) is a risk factor for antibody-mediated rejection and shortened graft survival. We investigated the role of intrapatient variability in tacrolimus trough levels on graft outcomes (i.e., de novo DSA, rejection, graft loss) in pediatric renal transplant recipients. METHODS: This was a single-center retrospective study which included 38 pediatric renal transplant recipients. Intrapatient tacrolimus variability was defined using the coefficient of variation (CV; SD/Mean × 100) for all levels obtained after 3 months post-transplant. CV cut-points of 30%, 40%, and 50% were used in the analyses. RESULTS: The median CV 43.1% (35.0%, 58.6%). Out of 38 patients, 19 (50%) developed de novo DSA. In the logistic regression model, after adjusting for age, rejection history, maintenance immunosuppression, and CV, for every 10% increase in tacrolimus variability, the odds of developing de novo DSA increased by 53% (p = 0.048, CI 1.0005, 1.11). Age at transplant was also an independent risk factor for DSA development; every 1 year increase in age was associated with a 31% increase in the odds of developing DSA (p = 0.03, CI 1.03, 1.67). At a CV cut-point ≥ 30%, higher tacrolimus variability was associated with an increased incidence of allograft rejection (0% vs 42%, < 30 and ≥ 30% respectively, p = 0.07). As there were few graft loss events (n = 4) in our study population, an association could not be determined between tacrolimus variability and graft loss. CONCLUSION: Tacrolimus variability and age at transplant were identified as independent risk factors for de novo DSA development. There was an association between tacrolimus variability and rejection in pediatric renal transplant recipients. Adding the assessment of tacrolimus variability to current monitoring methods may be an important step towards improving graft outcomes.

The prevalence and clinical significance of C1q-binding donor-specific anti-HLA antibodies early and late after kidney transplantation.

We aimed to determine the prevalence and clinical significance of complement-binding donor-specific antibodies (DSA) detected up to 30 years after kidney transplantation. Group 1 patients included 284 consecutive DSA negative patients who underwent kidney transplantation after 1 May 2009. Group 2 included 405 patients transplanted before this date and followed at our center with functioning allografts. DSA were tested using Luminex Single Antigen and the C1q assay. In Group 1 patients, who were monitored prospectively, 31 (11%) developed de novo DSA during a median follow-up of 2.5 (1.9, 3.6) years. Of these, 11 (4%) had C1q+ and 20 (7%) had C1q negative DSA. In Group 2 patients, 77 (19%) displayed DSA. Among these, 33 (8%) had C1q+ and 44 (11%) had C1q negative DSA. The incidence of acute antibody-mediated rejection (AMR) was significantly higher in C1q+DSA patients in both Group 1 (45%) and Group 2 (15%) compared with C1q negative DSA (5% and 2%) and DSA negative patients (1% and 3%; P < 0.001 and P = 0.001). The incidence of chronic AMR was 36% (Group 1) and 51% (Group 2) in patients with C1q+DSA. In contrast, chronic AMR occurred in 5% and 25% of C1q negative DSA, and 2% and 6% of DSA negative Group 1 and 2 patients, respectively (P < 0.001). Although the graft survival was lower in Group 1 C1q+DSA patients (73%) compared with C1q negative DSA (95%) and DSA negative (94%) patients, the difference was not statistically significant by Kaplan-Meier survival analysis (P = 0.21). Our results indicated that the presence of C1q+ DSA was associated with acute and chronic AMR.

Clinical and molecular significance of microvascular inflammation in transplant kidney biopsies.

The diagnostic criteria for antibody-mediated rejection (AMR) are continuously evolving. Here we investigated the clinical and molecular significance of different Banff microvascular inflammation (MVI) scores in transplant kidney biopsies. A total of 356 patients with clinically indicated kidney transplant biopsies were classified into three groups based on MVI scores of 0, 1, 2, or more for Groups 1-3, respectively. Gene expression profiles were assessed using arrays on a representative subset of 93 patients. The incidence of donor-specific anti-HLA antibodies was increased from 25% in Group 1 to 36% in Group 2 and to 54% in Group 3. Acute and chronic AMR were significantly more frequent in Group 3 (15% and 35%) compared with the Group 2 (3% and 15%) and Group 1 (0% and 5%), respectively. Gene expression profiles showed increased interferon-γ and rejection-induced, cytotoxic and regulatory T-cell, natural killer cell-associated and donor-specific antibody (DSA)-selective transcripts in Group 3 compared with Groups 1 and 2. There was no significant difference in gene expression profiles between the Groups 1 and 2. Increased intragraft expression of DSA-selective transcripts was found in the biopsies of C4d- Group 3 patients. Thus, an MVI score of 2 or more was significantly associated with a histological diagnosis of acute and chronic antibody-mediated rejection. Hence, increased intragraft DSA-selective gene transcripts may be used as molecular markers for AMR, especially in C4d- biopsies.

Pregnancy in sensitized kidney transplant recipients: a single-center experience.

BACKGROUND: We aimed to examine the clinical outcomes of sensitized pregnant kidney transplant recipients. METHODS: A retrospective cohort study of female patients who received kidney transplant at Montefiore transplant center between June 1, 2009 through December 31, 2014 and had a documented pregnancy in our system. RESULTS: We found that 11 women had pregnancies during this period with a median age of 36 yr (range 22, 39). Pregnancies occurred at a median of 3.1 yr (1.1, 8.7) after transplantation. Pre-pregnancy patients' median serum creatinine levels and spot urine protein/creatinine ratio were 1.1 mg/dL (1.1, 2.1) and 0.55 g/d (0, 1.2), respectively. Eight patients were sensitized with panel reactive antibody (PRA) levels > 0% and three had PRA of 0%. The sensitized group had a higher incidence of adverse pregnancy outcomes; one stillbirth and two second trimester miscarriage. During a median follow-up of 2.3 yr (1.2, 4) after delivery, three high PRA patients (37%) developed antibody-mediated rejection that led to graft loss. CONCLUSIONS: We observed an increased risk of rejection, graft loss, and adverse pregnancy outcomes in sensitized kidney recipients.

Increased intragraft rejection-associated gene transcripts in patients with donor-specific antibodies and normal biopsies.

We investigated why some donor-specific antibody-positive patients do not develop antibody-mediated rejection. Of 71 donor-specific antibody-positive patients, 46 had diagnosis of antibody-mediated rejection and 25 had normal biopsies. Fifty donor-specific antibody-negative patients with normal biopsies were used as a control group. A subgroup of 61 patients with available biopsy and 64 with blood samples were analyzed by microarrays. Both donor-specific antibody-positive/antibody-mediated rejection-positive and negative biopsies showed increased expression of gene transcripts associated with cytotoxic T cells, natural killer cells, macrophages, interferon-gamma, and rejection compared to donor-specific antibody-negative biopsies. Regulatory T-cell transcripts were upregulated in donor-specific antibody-positive/antibody-mediated rejection-positive and B-cell transcripts in donor-specific antibody-positive/antibody-mediated rejection-negative biopsies. Whole-blood gene expression analysis showed increased immune activity in only donor-specific antibody-positive/antibody-mediated rejection-positive but not negative patients. During a median follow-up of 36 months, 4 donor-specific antibody-positive/antibody-mediated rejection-negative patients developed antibody-mediated rejection, 12 continued to have donor-specific antibody, but 9 lost their donor-specific antibody. Gene expression profiles did not predict the development of antibody-mediated rejection or the persistence of donor-specific antibody. Thus, donor-specific antibody-positive/antibody-mediated rejection-negative patients had increased rejection-associated gene transcripts in their allografts despite no histologic findings of rejection but not in their blood. This was found in both biopsy and blood samples of donor-specific antibody-positive/antibody-mediated rejection-positive patients.

Analysis of Cross-sectional and Longitudinal HLA and Anti-viral Responses After COVID Infection in Renal Allograft Recipients: Differences and Correlates.

BACKGROUND: Characterization of anti-HLA versus anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) immune globulin isotypes in organ transplant recipients after coronavirus disease 2019 (COVID-19) infection has not been reported. We aimed to determine changes in anti-HLA antibodies in renal transplant patients with COVID-19 and compare the immunoglobulin and epitope-binding pattern versus anti-SARS-CoV-2 antibodies. METHODS: This is a cross-sectional study of 46 kidney transplant recipients including 21 with longitudinal sampling. Using a semi-quantitative multiplex assay, we determined immunoglobulin (Ig) M, IgA, IgG, and IgG1-2-3-4 antibodies against Class I and Class II HLA, and 5 SARS-CoV-2 epitopes including the nucleocapsid protein and multiple regions of the spike protein. RESULTS: Fourteen of 46 (30%) patients had donor-specific anti-HLA antibodies (donor-specific antibody [DSA]), 12 (26%) had non-DSA anti-HLA antibodies and 45 (98%) had anti-SARS-CoV-2 antibodies. Most DSAs targeted HLA-DQ (71%), with a dominant IgG isotype and IgG1 subtype prevalence (93%), and/or IgG3 (64%), followed by IgG2 (36%). Comparatively, there was a higher prevalence of IgA (85% versus 14%, P = 0.0001) and IgM (87%, versus 36%, P = 0.001) in the anti-SARS-CoV-2 antibody profile, when compared to DSAs, respectively. Anti-SARS-CoV-2 antibody profile was characterized by increased prevalence of IgM and IgA, when compared to DSAs. The median calculated panel reactive antibody before COVID-19 diagnosis (24%) tended to decrease after COVID-19 diagnosis (10%) but it was not statistically significant ( P = 0.1). CONCLUSIONS: Anti-HLA antibody strength and calculated panel reactive antibody in kidney transplant recipients after COVID-19 do not significantly increase after infection. Although the IgG isotype was the dominant form in both HLA and SARS-CoV-2 antigens, the alloimmune response had a low IgA pattern, whereas anti-SARS-CoV-2 antibodies were high IgA/IgM.

Aberrant T-cell antigen expression in B lymphoblastic leukaemia.

B lymphoblastic leukaemia (B-ALL) cells are characterized by the expression of various B-cell antigens. Expression of T/Natural Killer-cell antigens, however, has rarely been reported in B-ALL (TAg+ B-ALL), and the significance of this aberrant antigen expression is unclear. We thus analysed the frequency of TAg+ B-ALL at our institution and investigated its significance in the context of immunophenotypes, cytogenetic/molecular findings, and prognosis. We reviewed 134 consecutive cases of B-ALL and found 18 cases (13·4%) of TAg+ B-ALL. The most common aberrant T-cell antigens expressed were CD2, CD5, and CD7 at equivalent rates (each in six cases), CD4 (two cases), and CD56 (three cases). Adverse cytogenetic abnormalities were seen in a significantly larger proportion of the TAg+ cases (72·2%) than the TAg- cases (32·2%; P = 0·003). Multivariate Cox-regression analysis showed that the risk of relapse over time was higher in the TAg+ cases, independent of high risk status (based on age and white blood cell count) and the presence of adverse cytogenetic abnormalities (hazard ratio = 2·256, P = 0·065). These findings suggest that T-cell antigen expression in B-ALL may be an independent predictor of poor prognosis, and a useful marker to identify patients at increased risk for relapse and for harbouring adverse cytogenetic abnormalities.

A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature.

BACKGROUND: Kidney allocation system allows blood type B candidates accept kidneys from A2/A2B donors. There is no mandate by UNOS on which the anti-A2 level is acceptable. We aimed to investigate the safety of kidney transplant in blood group B patients with anti-A2 titers ≤16. METHODS: We performed 41 A2-incompatible kidney transplants in blood group B recipients between May 2015 and September 2019. Clinical outcomes were compared with a control group of 75 blood group B recipients who received blood group compatible kidney transplantation at the same period. RESULTS: Of the 41 recipients, 85% were male, 48% African American, with a median age of 53 (20-73) y. Thirty-eight (93%) were deceased-donor and 3 (7%) were living-donor kidney transplant recipients. Pretransplant anti-A2 IgG titers were 2 in 16, 4 in 9, 8 in 6, and 16 in 5 and too weak to titer in 5 recipients. Eight patients had pretransplant donor-specific antibodies. During a median follow-up of 32.6 mo (6-57.3) patient and graft survival were 100% and 92% in the A2-incompatible kidney transplant group, and 91% and 92% in the blood group compatible group, respectively. Twelve A2-incompatible recipients underwent a 21 clinically indicated kidney biopsies at a median 28 d (6-390) after transplantation. None of the patients developed acute antibody-mediated rejection and 2 patients (5%) had acute T-cell-mediated rejection. Interestingly, peritubular capillary C4d positivity was seen in 7 biopsies which did not have any findings of acute rejection or microvascular inflammation but not in any of the rejection-free biopsies in the control group. C4d positivity was persistent in 5 of those patients who had follow-up biopsies. CONCLUSIONS: A2-incompatible transplantation is safe in patients with anti-A2 titers ≤16 with excellent short-term kidney allograft outcomes. C4d positivity is frequent in allograft biopsies without acute rejection.

KHSV(-) EBV(-) post-transplant effusion lymphoma with plasmablastic features: variant of primary effusion lymphoma?

Primary effusion lymphoma (PEL) is a rare type of B-cell non-Hodgkin lymphoma (NHL), which predominantly occurs in HIV-infected individuals, and is pathogenetically linked with Kaposi sarcoma (KS)-associated herpes virus/human herpes virus-8 (KSHV/HHV-8) infection with or without evidence of Epstein-Barr virus (EBV) co-infection. Although uncommon, PELs have been reported in immunocompetent patients and recipients of solid organ allografts. Rare cases of KSHV(-) EBV(+) post-transplant effusion lymphomas resembling PEL have also been described, as have KSHV(-) EBV(-) effusion lymphomas, the latter including those arising in individuals with chronic liver disease. We report a unique KSHV(-) EBV(-) post-transplant effusion lymphoma associated with serum paraproteins, occurring in an HIV(-) individual, which had cytologic features and phenotype similar to PEL, and displayed a complex karyotype including isochromosome 12p and translocation t(8;22), resulting in rearrangement of c-MYC.

G6b-B cell surface inhibitory receptor expression is highly restricted to CD4+ T-cells and induced by interleukin-4-activated STAT6 pathway.

The G6b-B gene encodes a novel cell surface receptor of the immunoglobulin superfamily that activates inhibitory signaling pathways by triggering SHP-1/SHP-2 via immunoreceptor tyrosine-based inhibitory motifs (ITIM) in its cytoplasmic domain. We previously identified decreased G6b-B expression in peripheral blood mononuclear cells (PBMC) during acute cellular cardiac allograft rejection. We studied the expression of G6b-B in different human mononuclear cell populations and its regulation. Real-time polymerase chain reaction (PCR) revealed that G6b-B mRNA is higher in CD4+ T cells or monocytes, but is not different between CD25+ CD4+ T cells and CD25- CD4+ T cells. G6b-B mRNA was increased in CD4+ T cells in presence of interleukin-4 in dose- and time-dependent manners. To understand the regulatory mechanism, we analyzed a 1.9-kb 5'-flanking region of the G6b-B translation start site and found a putative cis-acting element for Signal Transducer and Activator of Transcription (STAT)-6. Luciferase-reporter-gene-assay and electrophoretic mobility shift assays identified the STAT6 site as necessary for the induction of G6b-B by IL-4. Our study demonstrates that G6b-B expression is highly restricted to peripheral CD4+ T cells and up-regulated by the IL-4-induced STAT6 pathway, strongly suggesting that G6b-B is involved in regulation of the immune response by CD4+ T cell-mediated and IL-4 induced regulatory mechanisms.

Expression of inhibitory receptor ILT3 on neoplastic B cells is associated with lymphoid tissue involvement in chronic lymphocytic leukemia.

T cell responses against leukemia-associated antigens have been reported in chronic lymphocytic leukemia (CLL). However, the relentless accumulation of CLL B cells in some patients indicates that anti-tumor immune responses are inefficient. Inhibitory receptors from the Ig-like transcript (ILT) family, such as ILT3 and ILT4, are crucial to the tolerogenic activity of antigen presenting cells. In this study, we examined the expression of ILT3 on CD5+ B cells obtained from 47 patients with CLL. Using flow cytometry and RT-PCR, we found that B CLL cells from 23 of 47 patients expressed ILT3 protein and mature ILT3 mRNA. ILT3 protein and mRNA were not found in normal B cells obtained from donors without CLL. Expression of ILT4 in normal and B CLL cells showed a pattern similar to ILT3. The frequency of ILT3 positive CLL B cells was higher in patients with lymphoid tissue involvement, suggesting that ILT3 may have prognostic value in CLL. Our findings indicate that expression of ILT3 and ILT4 on CLL B cells represents a phenotypic abnormality that may play a role in tolerization of tumor-specific T cells.

False positive hepatitis C antibody test results in left ventricular assist device recipients: increased risk with age and transfusions.

Left ventricular assist devices (LVADs) have been successfully used in patients with heart failure. However, LVADs may trigger immune activation, leading to higher frequencies of autoantibodies. We describe the clinical, epidemiological, and laboratory characteristics of LVAD recipients with false positive hepatitis C (FPHC) serology among 39 consecutive adult LVAD recipients who bridged to heart transplantation from January 2007 to January 2013 at Montefiore Medical Center. FPHC patients were identified as those with post-LVAD positive hepatitis C ELISA antibody tests and negative confirmatory testing with hepatitis C RNA PCR and/or radioimmunoblot assay. Ten (26%) patients previously seronegative for hepatitis C were found to have FPHC after device placement. Of the 39 patients, 32 had HeartMate II devices. The mean age at LVAD placement was 55 years. FPHC correlated with older age at the time of LVAD implantation and with receipt of packed red blood cell transfusions, but not with gender, fresh frozen plasma transfusions, panel reactive antibodies, globulin fraction, rheumatoid factor, or anticardiolipin antibodies. Clinicians should be aware of this increased risk of FPHC in older LVAD patients and those more heavily transfused in order to avoid unnecessary apprehension and possible delay in transplantation. Further studies should be done to evaluate the possible relationship between transfused blood products and immunomodulation.

Increased access to transplantation of highly sensitized patients under the new kidney allocation system. A single center experience.

We aimed to investigate the impact of the new kidney allocation system (KAS) on the rate of transplantation of sensitized patients at our center. Pre-KAS and post-KAS intervals were Jan 1st to Dec 3rd 2014 and Jan 1st 2015 to Dec 3rd 2015, respectively. The number of deceased-donor crossmatches performed by flow cytometry increased from 715 pre-KAS to 1188 post-KAS. The percent of crossmatches performed for sensitized patients with calculated panel reactive antibody (cPRA)>0% increased from 19% pre-KAS to 26% post-KAS (p<0.0001). The number of deceased-donor kidney transplants performed at our center increased from 115 pre-KAS to 125 post-KAS (9% increase). There was a significant increase in the percentage of deceased-donor kidney transplants received by sensitized candidates (from 14% to 26% pre- and post-KAS, respectively; p<0.0001). The highest increase was seen in the patients with cPRA>98%, from 0% to 9%, followed by the group with cPRA 50-79%, from 5% to 8%. This increase was balanced by a decrease of 12% in the percentage of non-sensitized recipients, and a modest decrease of 1% in the group with cPRA 1-49%. In conclusion, transplant rate has increased in sensitized patients after KAS. The highest increase was observed among highly sensitized patients (cPRA>98%).

Human Fc receptors: critical targets in the treatment of autoimmune diseases and transplant rejections.

The receptors for the Fc region of immunoglobulins (FcR) are members of the immunoglobulin superfamily. They are expressed on various hematopoietic cells and constitute a link between humoral and cell-mediated immunity. The activation and downmodulation of immune responses are controlled by signals from activating and inhibitory FcR, expressed on the surface of immune cells. The signaling regions, defined as immunoreceptor-tyrosine-based activation motif and immunoreceptor-tyrosine-based inhibitory motif, are contained within the cytoplasmic domain of FcR or of the adaptor proteins associated with FcR. Activating and inhibitory FcR are usually coexpressed on the surface of the same cell and coengaged by the same ligand, functioning in concert to keep a balanced immune response. Impairment of the functional balance between activating and inhibitory FcR leads either to hyperactivity to foreign and self antigens or to unresponsiveness as seen in many autoimmune diseases and infections. Pathologic conditions in which immunoglobulin-FcR interactions play a major role, as well as the outcome of treatment with intravenous immunoglobulin and monoclonal antibodies, may be influenced by targeting FcR.

Alloantibodies and the outcome of cadaver kidney allografts.

The role of humoral immunity in causing antibody-mediated rejection (AMR) of organ allografts has been extensively documented. For this reason, negative complement-dependent cytotoxicity (CDC) cross-matches between recipient sera and donor T and B lymphocytes have become a mandatory requirement for cadaveric kidney transplantation. However, the significance of donor-specific antibodies (DSAs) detectable only by flow cytometry (FC) or solid phase assays (SPA) but not CDC is still controversial. We have performed a retrospective analysis of FC cross-matching results in 80 consecutive cadaver kidney allograft recipients. Antibodies against HLA class I and class II antigens were measured by CDC and SPA in sequential samples of sera obtained prior to transplantation. The preoperative cross-match was performed by CDC using magnetically sorted T and B cells from donor spleen. Sera obtained from each patient before and at the time of transplantation were included in the final cross-match. The sample of serum obtained at the time of transplantation was cross-matched retrospectively by FC and analyzed for anti-HLA antibody specificity on high resolution SPA. The actuarial kidney allograft survival at one year was 98%. Two of these eighty patients lost the graft, one due to AMR, the other for reasons unrelated to DSAs. Donor-specific antibodies were detected by FC in 17 of 80 patients, yet only 6 of 17 had an early episode of AMR. This episode was successfully reversed by desensitization therapy using intravenous immunoglobin (IVIG) and plasmapheresis. Flow cytomery cross-matching showed 95% specificity but only 35% sensitivity for prediction of AMR (p = 0.002). There was a significant correlation between high panel reactive antibodies (PRA) and positive FC cross-matching (p = 0 .0001), as well as high PRA and AMR (p = 0.0004 by CDC and 0.0011 by Luminex). Reversible AMR occurred 12-30 days post-transplantation in 8 patients. Of these 8 patients, 3 had no detectable DSAs in spite of C4d positivity, 4 had C4d deposition in conjunction with anti-HLA antibodies, and 1 patient had DSAs (anti-MICA) yet no C4d deposition. We conclude that early initiation of desensitization protocols can prevent transplant failure and that retrospective FC cross-matches may facilitate the diagnosis of AMR. Extensive analysis of patients' sera using a comprehensive set of tests may contribute to early treatment and better understanding of the mechanism underlying humoral rejection.

Acute and hyperacute humoral rejection in kidney allograft recipients treated with anti-human thymocyte antibodies.

Equine and rabbit antihuman thymocyte globulins (ATGs) have been used in renal transplantation for prevention and treatment of acute rejection. We now report that hyperacute and acute antibody-mediated rejection of renal allografts occurred in three newly transplanted patients who received ATG for induction therapy. Antibody studies performed using complement-dependent cytotoxicity, flow cytometry, enzyme-linked immunosorbent assay, and Luminex yielded negative results for antilymphocytic and antiendothelial cell antibodies in the pretransplant sera obtained from these patients. ATG treatment was initiated at the time of transplantation. One of the patients experienced hyperacute rejection and required transplant nephrectomy within 24 h of transplantation. The other two patients developed acute antibody-mediated rejection within 14 days after transplantation. None of the patients developed antihuman leukocyte antigen antibodies when humoral rejection occurred. However, xenoantibodies that strongly bound to human lymphocytes and, importantly, to activated endothelial cells, were identified in the sera obtained at the time of humoral rejection. Hence, our results strongly implicate ATG in the induction of antibody-mediated rejection of kidney allografts. Flow cytometry testing of ATG reactivity to endothelial cells may be useful in identifying and discarding the ATG lots containing xenoantibodies that can bind to activated endothelial cells of the transplant.

Interleukin-10 induces the upregulation of the inhibitory receptor ILT4 in monocytes from HIV positive individuals.

A characteristic of human immunodeficiency virus infected individuals is an impairment of immune responses, which can result in opportunistic infections. Elevated levels of interleukin-10 (IL-10), produced by virally infected monocytes, are found in the sera of HIV infected individuals. Such elevated levels have been associated with the impaired function of CD4(+) and CD8(+) T cells, and antigen presenting cells (APC), such as monocytes. IL-10 has been reported to upregulate the cell surface expression of the inhibitory receptors ILT3 and ILT4 on monocytes and dendritic cells. This study demonstrates that the decreased antigen presenting ability of monocytes in HIV(+) individuals is in part due to the upregulation of ILT4 on the monocytes caused by the elevated serum IL-10 levels seen in these individuals.