title: Hypogammaglobulinaemia occurs in Fas-deficient MRL-lpr mice following deletion of MHC class II molecules.
abstract: Fas (CD95)-mediated apoptosis in B and T cells is deficient in both human autoimmune lymphoproliferative syndrome and in MRL-lpr mice, a model for systemic lupus erythematosis (SLE). Autoimmune disease in these mice is associated with polyclonal B cell activation, increased serum immunoglobulin and autoantibodies. In non-autoimmune mice MHC class II is not required for normal serum immunoglobulin expression, and previously we have shown using MHC class II-deficient MRL-lpr mice (MRL-lpr Ab-/-) that generation of specific antibodies to DNA requires MHC class II-directed T cell help. In contrast, in the present study we demonstrate that MRL-lpr Ab-/- mice also have a profound reduction of total serum immunoglobulin levels, suggesting abnormal polyclonal regulation of B cells by MHC class II-directed T cells occurs in the autoimmune MRL-lpr strain. This abrogation of immunoglobulin production does not occur in MHC class II-deficient non-obese diabetic (NOD) mice, nor in MHC class I-deficient NOD or MRL-lpr mice. Reduced immunoglobulin levels in MRL-lpr Ab-/- mice were not due to a lack of B cells or to an increased loss of circulating immunoglobulin, but were associated with reduced numbers of surface IgG-positive B cells. These results define a general abnormal regulation of B cells in MRL-lpr mice through a process requiring MHC class II, and suggest that Fas deficiency may allow expansion of totally T-dependent B cells.
authors.affiliation: Department of Microbiology and Immunology, University of Western Ontario, London, Canada.
authors.forename: C C
authors.initials: CC
authors.lastname: Anderson
authors.forename: R
authors.initials: R
authors.lastname: Mukherjee
authors.forename: N R
authors.initials: NR
authors.lastname: Sinclair
authors.forename: A M
authors.initials: AM
authors.lastname: Jevnikar
mesh_terms: D000361:Agammaglobulinemia / Q000276:immunology*; D000818:Animals; D000974:Antibodies, Antinuclear / Q000032:analysis; D015551:Autoimmunity; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D007108:Immune Tolerance; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D007136:Immunoglobulins / Q000096:biosynthesis / Q000276:immunology; D051379:Mice; D019463:Mice, Inbred MRL lpr / Q000276:immunology*; D016688:Mice, Inbred NOD / Q000276:immunology; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D019014:fas Receptor / Q000276:immunology*
chemical_list: D000974:Antibodies, Antinuclear; D000949:Histocompatibility Antigens Class II; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007136:Immunoglobulins; D019014:fas Receptor