Comparison of COVID-19 Vaccine-Associated Myocarditis and Viral Myocarditis Pathology.

The COVID-19 pandemic has led to significant loss of life and severe disability, justifying the expedited testing and approval of messenger RNA (mRNA) vaccines. While found to be safe and effective, there have been increasing reports of myocarditis after COVID-19 mRNA vaccine administration. The acute events have been severe enough to require admission to the intensive care unit in some, but most patients fully recover with only rare deaths reported. The pathways involved in the development of vaccine-associated myocarditis are highly dependent on the specific vaccine. COVID-19 vaccine-associated myocarditis is believed to be primarily caused by uncontrolled cytokine-mediated inflammation with possible genetic components in the interleukin-6 signaling pathway. There is also a potential autoimmune component via molecular mimicry. Many of these pathways are similar to those seen in viral myocarditis, indicating a common pathophysiology. There is concern for residual cardiac fibrosis and increased risk for the development of cardiomyopathies later in life. This is of particular interest for patients with congenital heart defects who are already at increased risk for fibrotic cardiomyopathies. Though the risk for vaccine-associated myocarditis is important to consider, the risk of viral myocarditis and other injury is far greater with COVID-19 infection. Considering these relative risks, it is still recommended that the general public receive vaccination against COVID-19, and it is particularly important for congenital heart defect patients to receive vaccination for COVID-19.

Autophagy and the Bone Marrow Microenvironment: A Review of Protective Factors in the Development and Maintenance of Multiple Myeloma.

The role of the unfolded protein response (UPR) in plasma cells (PC) and their malignant multiple myeloma (MM) counterparts is a well described area of research. The importance of autophagy in these cells, as well as the interplay between autophagy and the UPR system, has also been well studied. In this review, we will discuss the relationship between these two cellular responses and how they can be utilized in MM to account for the high levels of monoclonal immunoglobulin (Ig) protein synthesis that is characteristic of this disease. Interactions between MM cells and the bone marrow (BM) microenvironment and how MM cells utilize the UPR/autophagy pathway for their survival. These interacting pathways form the foundation for the mechanism of action for bortezomib, a proteasome inhibitor used to modify the progression of MM, and the eventual drug resistance that MM cells develop. One important resistance pathway implicated in MM progression is caspase 10 which attenuates autophagy to maintain its prosurvival function and avoid cell death. We lay a groundwork for future research including 3D in vitro models for better disease monitoring and personalized treatment. We also highlight pathways involved in MM cell survival and drug resistance that could be used as new targets for effective treatment.

MHC haplotype and B cell autoimmunity: Correlation with pathogenic IgG autoantibody subclasses and Fc glycosylation patterns.

Genome-wide association studies (GWAS) have identified many genes that are associated with the development of certain autoimmune disorders, but the MHC haplotypes still represent the most prevalent genetic risk factor for many autoimmune diseases. The mechanisms by which MHC-associated genetic susceptibility translates into B cell autoimmunity and the development of autoimmune diseases are complex. There is increasing evidence that the MHC haplotype modulates autoreactive B cell responses in multiple ways. Instead of merely inhibiting the production of IgG autoantibodies and mediating complete immunological tolerance, the non-permitting MHC haplotypes seem to facilitate the production of IgG autoantibodies exhibiting Fc glycosylation patterns that are associated with reduced pathogenicity and a protective cytokine profile of T follicular helper (Tfh) cells. Here, we discuss mechanisms linking MHC haplotypes to the production of pathogenic IgG autoantibodies, which could be relevant for the development of improved diagnosis, particularly in the context of individual medicine.

Structural and Ultrastructural Analysis of the Multiple Myeloma Cell Niche and a Patient-Specific Model of Plasma Cell Dysfunction.

Multiple myeloma (MM) is a deadly, incurable malignancy in which antibody-secreting plasma cells (PCs) become neoplastic. Previous studies have shown that the PC niche plays a role cancer progression. Bone marrow (BM) cores from MM and a premalignant condition known as monoclonal gammopathy of unknown significance (MGUS) patients were analyzed with confocal and transmission electron microscopy. The BM aspirates from these patients were used to generate 3D PC cultures. These in vitro cultures were then assayed for the molecular, cellular, and ultrastructural hallmarks of dysfunctional PC at days 1 and 5. In vivo, evidence of PC endoplasmic reticulum stress was found in both MM and MGUS BM; however, evidence of PC autophagy was found only in MM BM. Analysis of in vitro cultures found that MM PC can survive and maintain a differentiated phenotype over an unprecedented 5 days, had higher levels of paraprotein production when compared to MGUS-derived cultures, and showed evidence of PC autophagy as well. Increased fibronectin deposition around PC associated with disease severity and autophagy dysregulation was also observed. 3D cultures constructed from BM aspirates from MGUS and MM patients allow for long-term culture of functional PC while maintaining their distinct morphological phenotypes.

Metabolomic Profiles of Men and Women Ischemic Stroke Patients.

BACKGROUND: Stroke is known to affect both men and women; however, incidence and outcomes differ between them. Therefore, the discovery of novel, sex-specific, blood-based biomarkers for acute ischemic stroke (AIS) patients has the potential to enhance the understanding of the etiology of this deadly disease in the content of sex. The objective of this study was to identify serum metabolites associated with male and female AIS patients. METHODS: Metabolites were measured with the use of untargeted, reverse-phase ultra-performance liquid chromatography-tandem mass spectrometry quantification from blood specimens collected from AIS patients. Samples were collected from 36 patients comprising each of 18 men and women with matched controls. Metabolic pathway analysis and principal component analysis (PCA) was used to differentiate metabolite profiles for male and female AIS patients from the control, while logistic regression was used to determine differences in metabolites between male and female AIS patients. RESULTS: In female AIS patients, 14 distinct altered metabolic pathways and 49 corresponding metabolites were identified, while 39 metabolites and 5 metabolic pathways were identified in male patients. Metabolites that are predictive of ischemic stroke in female patients were 1-(1-enyl-palmitoyl)-2-arachidonoyl-GPC (P-16:0/20:4) (AUC = 0.914, 0.765-1.000), 1-(1-enyl-palmitoyl)-2-palmitoyl-GPC (P-16:0/16:0) (AUC = 0.840, 0.656-1.000), and 5,6-dihydrouracil (P-16:0/20:2) (AUC = 0.815, 0.601-1.000). Significant metabolites that were predictive of stroke in male patients were 5alpha-androstan-3alpha,17beta-diol disulfate (AUC = 0.951, 0.857-1.000), alpha-hydroxyisocaproate (AUC = 0.938, 0.832-1.000), threonate (AUC = 0.877, 0.716-1.000), and bilirubin (AUC = 0.817, 0.746-1.000). CONCLUSIONS: In the current study, the untargeted serum metabolomics platform identified multiple pathways and metabolites associated with male and female AIS patients. Further research is necessary to characterize how these metabolites are associated with the pathophysiology in male and female AIS patients.

Immunomodulatory regulation by heat-labile enterotoxins and potential therapeutic applications.

Introduction: Heat-labile enterotoxins (HLTs) and their cognate ganglioside receptors have been extensively studied because of their therapeutic potential. Gangliosides play arole in modulating effector cells of the immune system, and HLTs provide a novel means for stimulating ganglioside-mediated responses in immunocompetent cells.Areas covered: To evaluate the mechanisms of HLT adjuvanticity, a systemic literature review was performed using relevant keyword searches of the PubMed database, accessing literature published as recently as late 2020. Since HLTs bind to specific ganglioside receptors on immunocytes, they can act as regulators via stimulation or tapering of immune responses from associated signal transduction events. Binding of HLTs to gangliosides can increase proliferation of T-cells, increase cytokine release, augment mucosal/systemic antibody responses, and increase the effectiveness of antigen presenting cells. Subunit components also independently stimulate certain immune responses. Mutant forms of HLTs have potent immunomodulatory effects without the toxicity associated with holotoxins.Expert opinion: HLTs have been the subject of abundant research exploring their use as vaccine adjuvants, in the treatment of autoimmune conditions, in cancer therapy, and for weight loss, proving that these molecules are promising tools in the field of immunotherapy.

Serie de Casos de Leishmaniasis Detectados en Centros Hospitalarios del Departamento de Caaguazú, Paraguay en 2019

Resumen La leishmaniasis es la tercera de las enfermedades de transmisión vectorial a humanos en importancia por el número de casos y la población en riesgo. En Paraguay la leishmaniasis cutánea es una enfermedad endémica atribuida en casi todos los casos a Leishmania (Viannia) braziliensis. El objetivo del artículo es describir las características demográficas y clínicas de una serie de casos de pacientes con leishmaniasis en el V departamento de Caaguazú y departamentos cercanos, epidemiológicamente endémicos. Se reportan casos diagnosticados en los meses enero a diciembre del año 2019. Los casos se presentaron en el departamento de Caaguazú, abarcando los diferentes distritos que componen y departamentos cercanos como Canindeyú, Alto Paraná y Guaira. De los casos registrados (9 casos) fueron hombres y (6 casos) tuvieron entre 50 a 70 años de edad. La lesión estuvo situada mayormente en el tabique nasal en 8 casos, con una evolución de menos de 10 años (6 casos) y en 4 casos dejo cicatriz. Solo 3 casos completaron su tratamiento. Se sugiere realizar el reporte de casos para tener un panorama de los casos de leishmaniasis en Paraguay como vigilancia sanitaria de la enfermedad y localizar focos de contagio.

Abstract Leishmaniasis is the third most important vector-borne diseases in humans due to the number of cases and the population at risk. In Paraguay, cutaneous leishmaniasis is an endemic disease attributed in almost all cases to Leishmania (Viannia) braziliensis. The objective of the article was to describe the demographic and clinical characteristics of a series of cases of patients with leishmaniasis in the V department of Caaguazú and nearby departments, epidemiologically endemic. Cases diagnosed in the months of January to December of the year 2019 are reported. The cases occurred in the department of Caaguazú, covering the different districts that make up and nearby departments such as Canindeyú, Alto Paraná and Guaira. Of the registered cases (9 cases) were men and (6 cases) were between 50 and 70 years of age. The lesion was located mainly in the nasal septum in 8 cases, with an evolution of less than 10 years (6 cases) and in 4 cases it left a scar. Only 3 cases completed their treatment. It is suggested to carry out the case report to have an overview of Leishmania cases in Paraguay as a health surveillance of the disease and to locate sources of contagion.

Two Acinetobacter baumannii Isolates Obtained From a Fatal Necrotizing Fasciitis Infection Display Distinct Genomic and Phenotypic Characteristics in Comparison to Type Strains.

Acinetobacter baumannii has been recognized as a critical pathogen that causes severe infections worldwide not only because of the emergence of extensively drug-resistant (XDR) derivatives, but also because of its ability to persist in medical environments and colonize compromised patients. While there are numerous reports describing the mechanisms by which this pathogen acquires resistance genes, little is known regarding A. baumannii's virulence functions associated with rare manifestations of infection such as necrotizing fasciitis, making the determination and implementation of alternative therapeutic targets problematic. To address this knowledge gap, this report describes the analysis of the NFAb-1 and NFAb-2 XDR isolates, which were obtained at two time points during a fatal case of necrotizing fasciitis, at the genomic and functional levels. The comparative genomic analysis of these isolates with the ATCC 19606T and ATCC 17978 strains showed that the NFAb-1 and NFAb-2 isolates are genetically different from each other as well as different from the ATCC 19606T and ATCC 17978 clinical isolates. These genomic differences could be reflected in phenotypic differences observed in these NFAb isolates. Biofilm, cell viability and flow cytometry assays indicate that all tested strains caused significant decreases in A549 human alveolar epithelial cell viability with ATCC 17978, NFAb-1 and NFAb-2 producing significantly less biofilm and significantly more hemolysis and capacity for intracellular invasion than ATCC 19606T. NFAb-1 and NFAb-2 also demonstrated negligible surface motility but significant twitching motility compared to ATCC 19606T and ATCC 17978, likely due to the presence of pili exceeding 2 µm in length, which are significantly longer and different from those previously described in the ATCC 19606T and ATCC 17978 strains. Interestingly, infection with cells of the NFAb-1 isolate, which were obtained from a premortem blood sample, lead to significantly higher mortality rates than NFAb-2 bacteria, which were obtained from postmortem tissue samples, when tested using the Galleria mellonella in vivo infection model. These observations suggest potential changes in the virulence phenotype of the A. baumannii necrotizing fasciitis isolates over the course of infection by mechanisms and cell processes that remain to be identified.

Efficacy of therapeutic plasma exchange in the treatment of penn class 3 and 4 cytokine release syndrome complicating COVID-19.

OBJECTIVES: Cytokine release syndrome (CRS) is a potentially severe complication of COVID-19 most commonly resulting in respiratory failure. This ten-patient study was designed to determine the efficacy of therapeutic plasma exchange (TPE) in improving oxygenation and in reducing the cytokine load in a critically ill subset of patients. METHODS: Five single volume plasma exchanges over eight days within a 14-day study period. In mechanically ventilated patients, oxygenation was measured via the PaO2/FiO2 (P/F) ratio and the oxygenation index (OI) daily for 14 days. Supplemental oxygen requirements were tracked daily for non-ventilated patients. RESULTS: Non-ventilated patients were liberated from supplemental oxygen after TPE. The response was rapid with an 87% average reduction in oxygenation requirements following and average time to return to room air of 5.25 days. All mechanically ventilated patients demonstrated improvement in oxygenation with a 78% average improvement in the P/F ratio and a 43% improvement in OI. C-reactive protein (CRP) and serum levels of IL-6, IL-8, IL-10, TNFα, IFNγ and GM-CSF, were measured daily with immediate post TPE levels drawn on days 1, 2, 4, 6 and 8. All patients demonstrated significant reductions in CRP, IL-6, IL-10 and TNFα. CONCLUSIONS: In the majority of patients with Penn class 3 and 4 CRS complicating COVID-19, TPE demonstrated a prompt improvement in oxygenation and reduction in cytokine load without compromising patient safety. As this pilot study was envisioned to be hypothesis generating, expanded trials using TPE alone and in conjunction with novel pharmacologic agents are warranted. REGISTRATION: ClinicalTrials.gov NCT04374149.

Key Players and Biomarkers of the Adaptive Immune System in the Pathogenesis of Sarcoidosis.

Sarcoidosis is a systemic inflammatory disease characterized by development of granulomas in the affected organs. Sarcoidosis is often a diagnosis of exclusion, and traditionally used tests for sarcoidosis demonstrate low sensitivity and specificity. We propose that accuracy of diagnosis can be improved if biomarkers of altered lymphocyte populations and levels of signaling molecules involved in disease pathogenesis are measured for patterns suggestive of sarcoidosis. These distinctive biomarkers can also be used to determine disease progression, predict prognosis, and make treatment decisions. Many subsets of T lymphocytes, including CD8+ T-cells and regulatory T-cells, have been shown to be dysfunctional in sarcoidosis, and the predominant CD4+ T helper cell subset in granulomas appears to be a strong indicator of disease phenotype and outcome. Studies of altered B cell populations, B cell signaling molecules, and immune complexes in sarcoidosis patients reveal promising biomarkers as well as possible explanations of disease etiology. Furthermore, examined biomarkers raise questions about new treatment methods and sarcoidosis antigens.

Immune response biomarkers as indicators of sarcoidosis presence, prognosis, and possible treatment: An Immunopathogenic perspective.

Sarcoidosis has been a disease of puzzling occurrence and clinical course. Multiple immunological markers have been noted to be altered within sarcoidosis, however there is variable consistency among these reports. Previous studies have shown sarcoidosis to be a primary T cell-mediated disease, yet new data concerning B cell and mycobacterial involvement have been brought to light. The possibility of a uniform biomarker to characterize sarcoidosis presence, severity and prognosis greatly increases the movement towards directed and specialized treatment for this rare disease.

Virus reactivation: a panoramic view in human infections.

Viruses are obligate intracellular parasites, relying to a major extent on the host cell for replication. An active replication of the viral genome results in a lytic infection characterized by the release of new progeny virus particles, often upon the lysis of the host cell. Another mode of virus infection is the latent phase, where the virus is 'quiescent' (a state in which the virus is not replicating). A combination of these stages, where virus replication involves stages of both silent and productive infection without rapidly killing or even producing excessive damage to the host cells, falls under the umbrella of a persistent infection. Reactivation is the process by which a latent virus switches to a lytic phase of replication. Reactivation may be provoked by a combination of external and/or internal cellular stimuli. Understanding this mechanism is essential in developing future therapeutic agents against viral infection and subsequent disease. This article examines the published literature and current knowledge regarding the viral and cellular proteins that may play a role in viral reactivation. The focus of the article is on those viruses known to cause latent infections, which include herpes simplex virus, varicella zoster virus, Epstein-Barr virus, human cytomegalovirus, human herpesvirus 6, human herpesvirus 7, Kaposi's sarcoma-associated herpesvirus, JC virus, BK virus, parvovirus and adenovirus.

Disturbed homeostasis and multiple signaling defects in the peripheral blood B-cell compartment of patients with severe chronic sarcoidosis.

The presence of hypergammaglobulinemia, autoantibodies, and circulating immune complexes suggests that humoral immunity may contribute to the pathogenesis of sarcoidosis. However, little is known about the role played by B cells in the development of this disease. Here we investigated the subpopulation distribution, response to stimulation, and levels of the nuclear transcription factor NF-κB/p65 in peripheral blood B cells from patients with severe chronic sarcoidosis. Patients with severe chronic sarcoidosis had absolute B-cell lymphopenia and exhibited significantly decreased frequencies and total numbers of memory (CD19(+) CD27(+)) B cells. The reduced numbers of memory B cells in these patients reflected a decrease in the total numbers of class-switched (CD19(+) CD27(+) IgD(-)) and unswitched (CD19(+) CD27(+) IgD(+)) memory B cells and coincided with an increased frequency of circulating (CD19(+/-) CD20(-) CD27(++)) plasmablasts. Polyclonal stimulation of sarcoid B cells resulted in reduced expression of activation markers (i.e., CD25, CD69, and CD86), decreased proliferation, and impaired plasma cell differentiation. Baseline expression of p65 in B cells was reduced in 65% of the patients. These results suggest disturbed homeostasis, intrinsic signaling defects, and anergy within the peripheral B-cell compartments of patients with severe chronic sarcoidosis.

Low levels of NF-κB/p65 mark anergic CD4+ T cells and correlate with disease severity in sarcoidosis.

T lymphocytes from patients with sarcoidosis respond weakly when stimulated with mitogen or antigen. However, the mechanisms responsible for this anergy are not fully understood. Here, we investigated the protein levels of nuclear transcription factor NF-κB (p50, p65, and p105), IκBα (inhibitor of NF-κB), T-cell receptor (TCR) CD3ζ-chain, tyrosine kinase p56(LCK), and nuclear factor of activated T cells c2 (NF-ATc2) in peripheral blood CD4(+) T cells from patients with sarcoidosis. Baseline expression of p65 in these lymphocytes was reduced in 50% of patients. The reduced levels of p65 in sarcoid CD4(+) T cells concurred with decreased levels of p50, p105, CD3ζ, p56(LCK), IκBα, and NF-ATc2. Polyclonal stimulation of NF-κB-deficient sarcoid T cells resulted in reduced expression of CD69 and CD154, decreased proliferation, and cytokine (i.e., interleukin 2 [IL-2] and gamma interferon [IFN-γ]) production. The clinical significance of these findings is suggested by the association between low p65 levels and the development of more severe and active sarcoidosis. Although correlative, our results support a model in which multiple intrinsic signaling defects contribute to peripheral T-cell anergy and the persistence of chronic inflammation in sarcoidosis.

Cuba's kidney transplantation program.

The first kidney transplant in Cuba was performed on 24 February 1970, using a cadaveric donor. In 1979, living donor kidney transplantation began between first-degree relatives. A total of 2775 patients are enrolled in renal replacement therapy in 47 hospitals across the country, 1440 of whom are awaiting kidney transplantation. Organs for the kidney program are procured in 63 accredited hospitals equipped for multidisciplinary management of brain death. Accordingly, over 90% of transplanted kidneys are from cadaveric donors. Identification of potential recipients is carried out through a national, computerized program that affords all patients the same opportunity regardless of distance from a transplant center, and selection of the most suitable candidate is based primarily on HLA compatibility. KEYWORDS Chronic renal failure, kidney transplantation.

Deletion of PPAR gamma in alveolar macrophages is associated with a Th-1 pulmonary inflammatory response.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is constitutively expressed at high levels in healthy alveolar macrophages, in contrast to other tissue macrophages and blood monocytes. PPARgamma ligands have been shown to down-regulate IFN-gamma-stimulated inducible NO synthase (iNOS) in macrophages. Because NO is an important inflammatory mediator in the lung, we hypothesized that deletion of alveolar macrophage PPARgamma in vivo would result in up-regulation of iNOS and other inflammatory mediators. The loss of PPARgamma in macrophages was achieved by crossing floxed (+/+) PPARgamma mice and a transgenic mouse containing the CRE recombinase gene under the control of the murine M lysozyme promoter (PPARgammaKO). Alveolar macrophages were harvested by bronchoalveolar lavage (BAL). Lymphocytes (CD8:CD4 ratio = 2.8) were increased in BAL of PPARgammaKO vs wild-type C57BL6; p < or = 0.0001. Both iNOS and IFN-gamma expression were significantly elevated (p < or = 0.05) in BAL cells. Th-1 associated cytokines including IL-12 (p40), MIP-1alpha (CCL3), and IFN inducible protein-10 (IP-10, CXCL10) were also elevated. IL-4 and IL-17A were not detected. To test whether these alterations were due to the lack of PPARgamma, PPARgamma KO mice were intratracheally inoculated with a PPARgamma lentivirus construct. PPARgamma transduction resulted in significantly decreased iNOS and IFN-gamma mRNA expression, as well as reduced BAL lymphocytes. These results suggest that lack of PPARgamma in alveolar macrophages disrupts lung homeostasis and results in a Th1-like inflammatory response.

In vitro induction of immunoglobulin A (IgA)- and IgM-secreting plasma blasts by cholera toxin depends on T-cell help and is mediated by CD154 up-regulation and inhibition of gamma interferon synthesis.

Cholera toxin (CT) and the type II heat-labile enterotoxins (LT-IIa and LT-IIb) are potent immunological adjuvants which are hypothesized to enhance the production of antibody (Ab)-secreting cells, although their mechanisms of action are not fully understood. The treatment of splenic cells with concanavalin A (ConA) plus CT enhanced the production of immunoglobulin A (IgA) and IgM by dividing cells that expressed high levels of major histocompatibility complex class II (MHC-II), CD19, and CD138 and low levels of B220 a phenotype characteristic of plasma blasts. LT-IIa or LT-IIb moderately enhanced IgA and IgM production without enhancing plasma blast differentiation. CT up-regulated CD25, CD69, CD80, CD86, and MHC-II in isolated B cells but failed to induce proliferation or differentiation. The treatment of unfractionated splenic cells with ConA plus CT induced B-cell proliferation and differentiation, but the elimination of CD4(+) T cells inhibited this effect. CT treatment of ConA-activated CD4(+) T cells up-regulated CD134 and CD154, whereas the blockage of CD40-CD154 interactions inhibited the induction of plasma blasts and Ig synthesis. The treatment of unfractionated splenic cells with CT, LT-IIa, or LT-IIb enhanced the production of interleukin-6 (IL-6) and IL-10, whereas the production of gamma interferon was inhibited in both CD4(+) and CD8(+) T cells mostly by CT. Thus, major regulatory effects of CT on lymphocytes are likely exerted early during the induction of immune responses when B and T cells initially encounter antigen. Neither LT-IIa or LT-IIb had these effects, indicating that type II enterotoxins augment Ab responses by other mechanisms.

Mutants of type II heat-labile enterotoxin LT-IIa with altered ganglioside-binding activities and diminished toxicity are potent mucosal adjuvants.

The structure and function LT-IIa, a type II heat-labile enterotoxin of Escherichia coli, are closely related to the structures and functions of cholera toxin and LT-I, the type I heat-labile enterotoxins of Vibrio cholerae and enterotoxigenic Escherichia coli, respectively. While LT-IIa is a potent systemic and mucosal adjuvant, recent studies demonstrated that mutant LT-IIa(T34I), which exhibits no detectable binding activity as determined by an enzyme-linked immunosorbent assay, with gangliosides GD1b, GD1a, and GM1 is a very poor adjuvant. To evaluate whether other mutant LT-IIa enterotoxins that also exhibit diminished ganglioside-binding activities have greater adjuvant activities, BALB/c mice were immunized by the intranasal route with the surface adhesin protein AgI/II of Streptococcus mutans alone or in combination with LT-IIa, LT-IIa(T14S), LT-IIa(T14I), or LT-IIa(T14D). All three mutant enterotoxins potentiated strong mucosal immune responses that were equivalent to the response promulgated by wt LT-IIa. All three mutant enterotoxins augmented the systemic immune responses that correlated with their ganglioside-binding activities. Only LT-IIa and LT-IIa(T14S), however, enhanced expression of major histocompatibility complex class II and the costimulatory molecules CD40, CD80, and CD86 on splenic dendritic cells. LT-IIa(T14I) and LT-IIa(T14D) had extremely diminished toxicities in a mouse Y1 adrenal cell bioassay and reduced abilities to induce the accumulation of intracellular cyclic AMP in a macrophage cell line.

Differential binding of Escherichia coli enterotoxins LT-IIa and LT-IIb and of cholera toxin elicits differences in apoptosis, proliferation, and activation of lymphoid cells.

Cholera toxin (CT), LT-IIa, and LT-IIb are potent adjuvants which induce distinct T-helper (Th)-cell cytokine profiles and immunoglobulin G (IgG) subclass and IgA antibody responses. To determine if the distinct immune regulatory effects observed for LT-IIa, LT-IIb, and CT are elicited by binding of the enterotoxins to their cognate ganglioside receptors, the lineages of lymphoid cells that interact with the three enterotoxins and their effects on various lymphocyte responses in vitro were evaluated. Binding patterns of LT-IIa, LT-IIb, and CT to several lymphoid cell populations were distinctive for each enterotoxin. LT-IIa and CT, but not LT-IIb, induced apoptosis in CD8(+) T cells. LT-IIa(T34I), a mutant with no detectable binding to gangliosides, did not induce apoptosis. Blockade of GM(1) on the surface of CD8(+) T cells by LT-IIa(T14I), a mutant that binds only to GM(1) but does not induce apoptosis, did not inhibit induction of apoptosis by LT-IIa. Mitogen-induced proliferation of CD8(+) T cells was abrogated by treatment with CT, while resting CD8(+) T cells which were sensitive to LT-IIa-induced apoptosis became more resistant to apoptosis after mitogen activation. Exposure to CT, but not to LT-IIa or LT-IIb, inhibited mitogen-driven CD4(+) T-cell proliferation and expression of CD25 and CD69. In mitogen-stimulated B cells, CT, but not LT-IIa or LT-IIb, enhanced expression levels of CD86, while only CT induced B-cell differentiation into plasma cells. Thus, LT-IIa, LT-IIb, and CT exhibit distinguishable immunomodulatory properties which are likely dependent upon their capacities to recognize different ganglioside receptors on lymphocytes.

Regulation of CXCR3 and CXCR4 expression during terminal differentiation of memory B cells into plasma cells.

C-X-C motif chemokine receptor 3 (CXCR3) and CXCR4 expressed on immunoglobulin G (IgG)-plasma-cell precursors formed in memory immune responses are crucial modulators of the homing of these cells. Here, we studied the regulation of the expression of these chemokine receptors during the differentiation of human memory B cells into plasma cells. We show that CXCR3 is absent on CD27- naive B cells but is expressed on a fraction of memory B cells, preferentially on those coexpressing IgG1. On differentiation into plasma-cell precursors, CXCR3+ memory B cells maintain the expression of this chemokine receptor. CXCR3- memory B cells up-regulate CXCR3 and migrate toward concentration gradients of its ligands only when costimulated with interferon gamma (IFN-gamma), but not interleukin 4 (IL-4), IL-1beta, IL-6, IFN-alpha, IFN-beta, or tumor necrosis factor alpha (TNF-alpha). In contrast, the differentiation of CXCR4- B cells into plasma cells is generally accompanied by the induction of CXCR4 expression. These results show that lack of CXCR4 expression on plasma-cell precursors is not a limiting factor for plasma-cell homing and that the expression of CXCR3 on memory B cells and plasma-cell precursors is induced by IFN-gamma, provided in human T helper type 1 (Th1)-biased immune responses. Once induced in memory B cells, CXCR3 expression remains part of the individual cellular memory.