[Immunohistochemical study of the submaxillaritis in MRL/1 mouse (lymphoproliferation and autoimmunity)]

MRL/1 mice, reported by Murphy and Roths, are lupus mice in which monogenic mutation has occurred. They are characterized by the expression of massive lymphoadenopathy, splenomegaly, arthritis and glomerulonephritis. These specific characters are attributable to the proliferation of abnormal T cells governed by an autosomal recessive gene, which is called a lymphoproliferative (lpr) gene. In this study, the author has studied the pathology of various organs in MRL/1 mice in relation to their ages. Investigated the pathogenesis of spontaneous submaxillaritis in MRL/1 mice and mechanism of its occurrence. Based on the immunological abnormalities in MRL/1 mice studied thus far, the mechanism of onset of submaxillaritis is believed to be as follows; (1) expression of the lpr gene leads to proliferation of T cells accompanied by focal lymphocyte infiltration in the submandibular gland; (2) the helper T function of these proliferating T cells induces polyclonal B cell activation (PBA); (2) PBA leads to the formation of numerous autoantibodies and anti-gp70 antibody whose antigen is the glycoprotein of endogenous retrovirus, resulting in the massive formation of immune complexes; (4) the immune complexes are deposited on the vascular wall, resulting in activation of the complement system; (5) infiltration of neutrophils and macrophages is induced; and (6) the lysosomal enzymes, released from these cells, effects as a cytotoxic mediator and damages the vascular wall. In brief, submaxillaritis accompanied by granulomatous vasculitis can be regarded as a Type III allergic response caused by immunological abnormalities which are genetically determined by the lpr gene; it is thought to be a subtype of immune complex disease.