Cross-linking of CD38 on hematopoietic cells induces activation, proliferation and differentiation of mature T and B cells and mediates apoptosis of myeloid and lymphoid progenitor cells. In addition to acting as a signaling receptor, CD38 is also an enzyme capable of producing several calcium-mobilizing metabolites, including cyclic adenosine diphosphate ribose (cADPR). It has been previously postulated that the calcium-mobilizing metabolites produced by CD38 may regulate its receptor-based activities. To test this hypothesis, we examined whether the enzyme activity of CD38 controls the apoptosis of an anti-CD38-stimulated leukemic B cell. We show that anti-CD38-induced apoptosis of Ba/F3 cells, a murine pro-B cell line, is not affected by blocking the calcium-mobilizing activity of cADPR or by inhibiting intracellular or extracellular calcium mobilization. In addition, we demonstrate that blocking CD38 enzyme activity with 2'-deoxy-2'-fluoro-nicotinamide arabinoside adenine dinucleotide has no effect on apoptosis and that Ba/F3 cells expressing catalytically inactive mutant forms of CD38 still undergo apoptosis upon CD38 cross-linking. Instead, we find that anti-CD38-induced apoptosis is dependent on tyrosine kinase and caspase activation, and that this process appears to be potentiated by the presence of membrane microdomains. Thus, the receptor-mediated functions of CD38 can be separated from its enzyme activity in a murine leukemic cell line, suggesting that CD38 plays multiple, but independent, biologic roles.
CD38 is a transmembrane protein expressed in B lymphocytes, and is able to induce responses as proliferation, differentiation or apoptosis. Several reports propose that CD38 deficiency accelerates autoimmune processes in murine models of autoimmune diabetes, lymphoproliferation and rheumatoid arthritis. Other reports have shown elevated CD38 expression in B and T cells from patients with autoimmunity; however, the role of CD38 is still unclear in the development of autoimmunity. Recently, it has been characterized as CD1d CD5 regulatory B cell subpopulation able to produce IL-10, and the loss of these cells exacerbates the autoimmunity in murine models. Here, we report that CD38 mice exhibited elevated titres of ANAS, anti-dsDNA autoantibodies from 12 months of age and were higher by 16 months of age and mice presented kidney damage. Interestingly, there is a reduction in the survival of CD38 mice compared to the WT. Furthermore, CD38 is highly expressed by CD1d CD5 regulatory B cells, and the agonistic anti-CD38 stimulus plus LPS was able to increase the percentage of this cell subset and its ability to induce IL-10 production. Together, these results suggest that CD38 could play a role in the control of autoimmune diseases through their expression on regulatory B cells.
Background Colostrum is the primary source of maternal immunoglobulin A (IgA) for the newborn. IgA participates in protection and regulation mechanisms of the immune response at the neonate’s mucosa. Several studies have evaluated infectious diseases and vaccine protocols effects during pregnancy on maternal milk IgA levels, with the aim to understand lactation protecting effect on newborn. However, most of their results demonstrated that there were no differences in the total IgA levels. In humans, IgA has two subclasses (IgA1 and IgA2), they have an anatomical distribution among mucosal compartments, their levels vary after antigen stimulation and are also seen to describe differential affinities in colostrum. Although there are differences between IgA subclasses in several compartments, these studies have excluded specific colostrum IgA1 and IgA2 determination. Methods We analyzed data from 900 women in Mexico City. With Pearson correlation, we compared the number of infectious episodes during their pregnancy that was associated with mucosal compartments (skin, respiratory and gastrointestinal tracts) and colostrum IgA subclasses. Results We show a correlation between increased colostrum IgA1 levels and the number of infectious episodes at respiratory tract and the skin. In contrast, infections at the gastrointestinal tract correlated with increased IgA2 amounts. Conclusions I nfections present during pregnancy at certain mucosal site increase specific IgA subclasses levels in human colostrum. These results will help in understanding infections and immunizations effects on maternal IgA at the mammary gland, and their impact on the development and protection of the newborn. Electronic supplementary material The online version of this article (10.1186/s40748-019-0104-x) contains supplementary material, which is available to authorized users.
CD40, a glycoprotein expressed on B lymphocytes plays an important role in B cell development, growth and differentiation. The ligand for the CD40 is a 39‐kDa glycoprotein (CD154) expressed onthe surface of activated T lymphocytes and is essential for thymus‐dependent humoral immunity. The expression of CD154 is tightly regulated and its transient expression reduces the chances of potentially deleterious bystander activation of B cells. Stimulation through CD40 has been studied in vitro by using antibodies against CD40, by membranes of activated T cells or lately, by CD154 transfected cells. In this work we have evaluated the outcome of CD40‐CD40 ligand interaction in vitro and in vivo by using CD154‐transfected L929 cells. In vitro assaysshowed that CD154‐L929 cells can induce on B cells: IL‐4‐dependent proliferation, up‐regulation of CD23, CD54 and class II molecules and can also rescue WEHI‐231 B cell lymphoma from anti‐IgM‐induced apoptosis. Interestingly, in vivo assays revealed that when CD154‐L929 cells were inoculated into the spleen, mice developed a strong but transient production of anti‐erythrocyte autoantibodies. Through B lymphocyte activation with CD154‐transfected L929 cells both in vitro and in vivo, our data reveal that enforced and prolonged expression of CD40 ligand overcomes the tightly regulated mechanisms of B cell activation, triggering the production of autoantibodies. This system might be used to evaluate the early steps of an autoimmune response and the role of CD40‐CD154 in the induction of primary responses in vivo.
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