Pemphigus are B-cell-mediated autoimmune diseases affecting skin and mucous membranes. They are characterized by the production of pathogenic autoantibodies directed against desmogleins (Dsg). In this prospective study, we treated 21 pemphigus patients with rituximab and analyzed immunological modifications induced by anti-CD20 immunotherapy. The total depletion of peripheral B cells led to a significant decrease of total serum IgM but not IgG levels. The B-cell depletion was followed by a progressive re-emergence of naive blood B lymphocytes, with one-third of them expressing a transitional CD19+CD38(high)CD24(high) phenotype. In most patients, clinical response to rituximab was closely related to the evolution of anti-Dsg autoantibodies that decreased in patients who achieved complete remission, whereas they remained unchanged or reincreased in relapsing patients. In contrast, serum antimicrobial IgG remained stable after rituximab treatment. B-cell repertoire analysis of three patients using immunoscope showed distortions of VH-IgM and VH-IgG immunoscope profiles before treatment, particularly clonal and oligoclonal expansions in some VH families, which were not found after B-cell reconstitution, following anti-CD20 immunotherapy. The depletion of autoreactive B cells leading to the elimination of anti-Dsg autoantibodies in most remitted patients and the restoration of a diverse B-cell repertoire by naive B lymphocytes may provide an explanation for the long-lasting efficacy of rituximab in pemphigus patients.

By pumping calcium from the cytosol to the ER, sarco/endoplasmic reticulum calcium ATPases (SERCAs) play a major role in the control of calcium signaling. We describe two SERCA1 splice variants (S1Ts) characterized by exon 4 and/or exon 11 splicing, encoding COOH terminally truncated proteins, having only one of the seven calcium-binding residues, and thus unable to pump calcium. As shown by semiquantitative RT-PCR, S1T transcripts are differentially expressed in several adult and fetal human tissues, but not in skeletal muscle and heart. S1T proteins expression was detected by Western blot in nontransfected cell lines. In transiently transfected cells, S1T homodimers were revealed by Western blot using mildly denaturing conditions. S1T proteins were shown, by confocal scanning microscopy, to colocalize with endogenous SERCA2b into the ER membrane. Using ER-targeted aequorin (erAEQ), we have found that S1T proteins reduce ER calcium and reverse elevation of ER calcium loading induced by SERCA1 and SERCA2b. Our results also show that SERCA1 variants increase ER calcium leakage and are consistent with the hypothesis of a cation channel formed by S1T homodimers. Finally, when overexpressed in liver-derived cells, S1T proteins significantly induce apoptosis. These data reveal a further mechanism modulating Ca2+ accumulation into the ER of nonmuscle cells and highlight the relevance of S1T proteins to the control of apoptosis.

The immune response to the synthetic terpolymer GAT is controlled by MHC-linked Ir gene(s). We show in this paper that antigen-presenting cells and T cells from mice belonging to two nonresponder strains (SJL and DBA/1) can present and recognize GAT, respectively. This has been measured with a T cell proliferation assay of GAT-primed lymph node cells. In order to detect T cell proliferation among GAT-primed lymph node cells from DBA/1 mice, it is necessary to treat the cells with monoclonal anti-Lyt-2 antibodies and complement (C) before the assay. These conclusions were further verified with SJL mice, when a T cell line derived from LN cells was used. We have shown that after immunization with GAT, specific T helper cells can be generated in the lymph nodes of SJL mice but not in the lymph nodes of DBA/1 mice. Furthermore, GAT-specific T helper cells can be detected in the spleen of SJL mice after immunizations with GAT, provided these spleen cells are pretreated with monoclonal anti-Lyt-2 antibodies + C or mild irradiation. Together, these results support the general idea that nonresponsiveness can be explained by a regulatory imbalance rather than by discrete cellular "defects."

Antigen-activated T helper (TH) cells secrete into their supernatant various lymphokines that are able to drive B cells to proliferate and to differentiate into Ig-secreting cells. In this report, we compared the production of these two types of activities by a TH clone. We found that B cell proliferating activity was released by TH cells under conditions in which T cell proliferation and the release of the B cell differentiating activity were totally blocked by anti-L3T4 monoclonal antibody GK1.5. The release of these two activities also dissociated during the reversion of T cells to the resting state after activation with antigen. Two weeks after activation, the T cell clone still secreted B cell proliferating activity, but did not secrete B cell differentiating activity. Three to four weeks after activation, neither activity was produced. The data suggest that the genes coding for these two activities are independently regulated in activated T cells. The implications of these observations concerning B lymphocyte development are discussed.