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International audience; Marked polyclonal immunoglobulin (Ig)G4 hypergammaglobulinemia has exceptionally been reported. Here we report on two Algerian patients who presented a syndrome characterized by anemia, plasmacytic lymphadenopathy, renal manifestations, and a marked polyclonal IgG4 hypergammaglobulinemia leading to a hyperviscosity syndrome in one case. The IgG4-expressing cell percentage was significantly increased in the peripheral blood lymphocytes collected from the two patients upon diagnosis. Moreover, in contrast with normal sera, both patients' sera significantly increased the percentage of IgG4-expressing cells when incubated with CD40-stimulated normal B lymphocytes. Similar effects were obtained with the culture supernatants of the patients' activated T cells. Anti-interleukin (IL) 4 and/or anti-IL-13 antibodies were unable to antagonize the IgG4 production. IL-4 and IL-13 serum concentrations were found to be normal in the two patients. The increased IgG4 production was found to be mediated by soluble factor(s), most probably secreted by activated T cells, which did not require the signal transducer and activator of transcription 6 signaling pathway.

We previously identified IgM autoantibodies in the sera of patients with Wiskott-Aldrich syndrome (WAS) that react with a subset of normal human B lymphocytes and induce B cell differentiation in vitro. From splenocytes of a patient with WAS we generated heterohybridomas (HY18 and HY21) and a lymphoblastoid cell line (LWA10) that produce human IgM lambda or IgM kappa anti-B lymphocyte autoantibodies, respectively. Immunohistochemical and multiparameter flow cytometric analyses demonstrate that these autoantibodies are specific for lymphocytes of the B lineage and preferentially stain B cells that reside in the mantle zone of secondary follicles and that constitutively co-express the CD5 surface antigen and most major autoantibody-associated cross-reactive idiotypes; in addition, these antibodies stain most pre-B cells in adult bone marrow. Molecular studies show that these anti-B lymphocyte autoantibodies are encoded by a highly conserved VH4 gene, designated VH4.21. The gene encodes a number of autoantibodies, especially anti-i and anti-I IgM cold agglutinins. Hemagglutination and surface labeling studies reveal that HY18 and LWA10 recognize the "i" carbohydrate antigenic determinant(s) which is classically found on human cord red blood cells and, as shown now by this study, on a subpopulation of human B cells which expresses it early in B cell development. These studies raise the possibility that the gene product encoded by this highly conserved germ-line VH4 gene may play a physiological role in B cell development and/or differentiation.

Marked polyclonal IgG4 hypergammaglobulinemia has exceptionally been reported. Here we report on two patients who presented an unique syndrome including a predominant and massive increase in serum levels of the IgG4 subclass. Clincal, biological and pathological data were described. Production of IgG4 by patients’ peripheral blood lymphocytes was studied, as well as the capacity of patients’ sera and T lymphocytes to induce IgG4 production by normal B cells. The possible involvement of IL4 and IL13 in the increased IgG4 production was also investigated. The two patients had anemia, lymphadenopathy, renal manifestations and a marked polyclonal IgG4 hypergammaglobulinemia leading to hyperviscosity syndrome in one case. The IgG4-producing cell percentage was significantly increased in both cases. By contrast with normal sera, both patients’ sera significantly increased the IgG4-producing cell percentagae when incubated with CD40-stimulated normal B lymphocytes. Similar effects were obtained with the culture supernatants of patients’ activated T cells. IL4 and IL13 serum concentrations were normal in the two patients. Anti-IL4 and/or anti-IL13 antibodies were unable to antagonize the IgG4 synthesis. The increased IgG4 production was found to be mediated by soluble, heat-resistant factor(s) that did not require the Stat6 signaling pathway. We described here a novel syndrome characterized by a significantly increased IgG4 production, mediated by soluble, heat-stable factor(s) most probably secreted by activated T cells, and distinct from IL4 and IL13.

In a young woman with ulcerative colitis, hypoimmunoglobulinemia, and humoral immunodeficiency, lymphocyte counts vary between 600 and 1,000 per mm(3) with 0.5-1.5% bone marrow-derived (B) cells and 98-99% thymus-derived (T) cells. Anti-lymphocyte antibodies were detected by immunofluorescence and by microlymphocytotoxicity with increased reactivity at +4 degrees C. They belonged to the IgM class and were polyclonal. Studies performed with various normal lymphocyte subpopulations, several lymphoblastoid cell lines and lymphocytes from immunodeficiency patients showed that these antibodies reacted with B cells. The corresponding antigen(s) is distinct from membrane-bound immunoglobulins, is not an alloantigen, and is probably unrelated to the la-like molecules. Pokeweed mitogen stimulated B cells appear to lose this antigen. Cells from various lymphoproliferative disorders were tested. T-derived and "non T-non-B" leukemic cells did not react with the antibody. Malignant cells from B-derived lymphomas and prolymphocytic leukemias were reactive. The incidence of positivity of the leukemic cells among patients with common B chronic lymphocytic leukemia was surprisingly low (one-third of the patients). The autoantibody nature of the anti-B-cell antibodies and their pathogenic role in the genesis of the patient's hypoimmunoglobulinemia was demonstrated by the effect of removal of antibodies by massive plasmaphereses which were followed by a dramatic and transitory increase of B-cell figures. Whereas most primary immunodeficiency syndromes appear to result from an arrest in the differentiation capabilities of immunologically competent cells, autoantibodies to circulating B lymphocytes may be incriminated in the pathogenesis of some cases of hypogammaglobulinemia.

It has been shown previously that chronic lymphocytic leukemia (CLL) B cells are frozen at different stages of activation with unique requirements for proliferation. Although most B CLL cells express surface IgM, anti-mu antibodies are able to trigger only some of them to proliferate and/or respond to B cell growth factor (BCGF) or interleukin 2 (IL2), as normal B cells. In this report we extend these observations using three different monoclonal antibodies (mAb) to human mu chain (one mitogenic in soluble form for normal B cells, the two others mitogenic only when coupled on Sepharose 4B beads). Cells from only 3 out of 11 B CLL patients proliferated in the presence of either mitogenic anti-mu. When the early events following surface Ig cross-linking, such as calcium mobilization (by flow cytometry on indo-1-labeled cells), were studied all three mAb in soluble form were able to induce a similar increase in the intracellular free calcium concentration ([Ca2+]i); analogous to [Ca2+]i rise after the mitogenic F(ab')2 anti-mu stimulation. This response was seen only in 8 out of the 12 CLL B cells studied. All B CLL cells, however, proliferate in response to a combination of phorbol ester 12,13-dibutyrate (PBt2) and ionomycin. Therefore, three patterns of response to sIg cross-linking by anti-mu could be distinguished: cells from 4 out of 12 cases proliferate and mobilize Ca2+ upon anti-mu triggering (behaving like resting B lymphocytes); in 4 other cases anti-mu lead to Ca2+ mobilization without cell proliferation; in the last 4 cases neither Ca2+ mobilization, IP3 generation (in the one case studied) nor cell proliferation are observed although these cells do proliferate directly in response to growth factors. Moreover, anti-mu stimulation in this group leads to increased proliferation in response to BCGF and IL2 suggesting an anti-Ig signaling independent of inositol phosphate metabolism. These results are interpreted in terms of differential anti-mu signaling on B cells at different stages of activation.

Twenty-five to 30 % of blood lymphocytes from a myeloma patient with an IgGl(k) protein with antibody activity to horse α2-macroglobulin (α2M) reacted with purified IgG from a rabbit antiserum to the idiotypic determinants of this protein. A small proportion of these idiotype-bearing lymphocytes were IgG-bearing B cells, but most of them were T cells. Several experiments demonstrated the actual synthesis of the idiotypic structures carried by the T lymphocytes. All idiotype-bearing lymphocytes bound horse α2M, and the structures that bore the idiotype and bound the antigen were shown to completely cocap. After biosynthetic labeling with 14C-labeled amino acids, immunoprecipitation and sodium dodecyl sulfate gel electrophoresis, the anti-idiotypic serum and the α2M antigen were found to react with the same molecules. Preliminary data on the size of these antigen-binding T lymphocyte-derived molecules are in accord with those of Binz and Wigzell (Scand. J. Immunol. 1976. 5: 559) in the rat. The finding in this patient with multiple myeloma of a homogeneous and possibly malignant population of T lymphocytes, synthesizing identical antigen receptors which share idiotypic (but not isotypic) determinants of the immunoglobulin molecule produced by the malignant B cell clone, therefore confirms in man the results of several recent studies in other mammalian species.