Impaired late suppression of Epstein-Barr virus (EBV)-induced immunoglobulin synthesis: a common feature of autoimmune disease

Fresh Insights into Disease Etiology and the Role of Microbial Pathogens

Pathogens have been implicated in the initiation and/or promotion of systemic sclerosis (scleroderma, SSc); however, no evidence was found to substantiate the direct contribution to this disease in past years. Recently, significant advances have been made in understanding the role of the innate immune system in SSc pathogenesis, supporting the idea that pathogens might interact with host innate immune-regulatory responses in SSc. In light of these findings, we review the studies that identified the presence of pathogens in SSc, along with studies on pathogens implicated in driving the innate immune dysregulation in SSc. The goal of this review is to illustrate how these pathogens, specifically viruses, may play important role both as triggers of the innate immune system, and critical players in the development of SSc disease.

CD8+ T-Cell Deficiency, Epstein-Barr Virus Infection, Vitamin D Deficiency, and Steps to Autoimmunity: A Unifying Hypothesis

CD8+ T-cell deficiency is a feature of many chronic autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, dermatomyositis, primary biliary cirrhosis, primary sclerosing cholangitis, ulcerative colitis, Crohn's disease, psoriasis, vitiligo, bullous pemphigoid, alopecia areata, idiopathic dilated cardiomyopathy, type 1 diabetes mellitus, Graves' disease, Hashimoto's thyroiditis, myasthenia gravis, IgA nephropathy, membranous nephropathy, and pernicious anaemia. It also occurs in healthy blood relatives of patients with autoimmune diseases, suggesting it is genetically determined. Here it is proposed that this CD8+ T-cell deficiency underlies the development of chronic autoimmune diseases by impairing CD8+ T-cell control of Epstein-Barr virus (EBV) infection, with the result that EBV-infected autoreactive B cells accumulate in the target organ where they produce pathogenic autoantibodies and provide costimulatory survival signals to autoreactive T cells which would otherwise die in the target organ by activation-induced apoptosis. Autoimmunity is postulated to evolve in the following steps: (1) CD8+ T-cell deficiency, (2) primary EBV infection, (3) decreased CD8+ T-cell control of EBV, (4) increased EBV load and increased anti-EBV antibodies, (5) EBV infection in the target organ, (6) clonal expansion of EBV-infected autoreactive B cells in the target organ, (7) infiltration of autoreactive T cells into the target organ, and (8) development of ectopic lymphoid follicles in the target organ. It is also proposed that deprivation of sunlight and vitamin D at higher latitudes facilitates the development of autoimmune diseases by aggravating the CD8+ T-cell deficiency and thereby further impairing control of EBV. The hypothesis makes predictions which can be tested, including the prevention and successful treatment of chronic autoimmune diseases by controlling EBV infection.

Atypical lymphoid infiltrates arising in cutaneous lesions of connective tissue disease

Atypical lymphoid infiltrates occurring in the setting of connective-tissue disease (CTD) comprise malignant neoplasms of B-cell or T-cell phenotypes and various reactive lymphoid hyperplasias, such as myoepithelial sialadenitis, lymphocytic thyroiditis, and lymphocytic interstitial pneumonitis. We describe 17 patients with atypical lymphoid infiltrates arising in cutaneous lesions of CTD, the spectrum of which included lupus erythematosus, dermatomyositis, relapsing polychondritis, and lichen sclerosus et atrophicus. There were two principal categories, pseudolymphoma and malignant lymphoma, the former representing 15 of the 17 cases. The clinical and histologic features and possible pathogenetic mechanisms are discussed.

Epstein-Barr virus-induced autoimmune responses. II. Immunoglobulin G autoantibodies to mimicking and nonmimicking epitopes. Presence in autoimmune disease

During infectious mononucleosis, IgM autoantibodies are generated to a protein, p542, which contains a glycine-rich 28-mer epitope cross-reactive with the Epstein-Barr nuclear antigen-1 through Epstein-Barr nuclear antigen-1's glycine/alanine repeat. In normal individuals it is uncommon to find IgG anti-p542, but among patients with progressive systemic sclerosis, systemic lupus erythematosus, and ulcerative colitis high IgG anti-p542 (> 3 SD above the mean of normal 20-50 yr controls) occurred frequently. Lesser elevations occurred in Sjögren's syndrome, rheumatoid arthritis, ankylosing spondylitis, and Crohn's disease, but none with chronic hepatitis B infection. The reactive epitopes on p542 were mapped with deletion mutants, which indicated that the glycine-rich 28-mer was the major antigenic determinant, with lesser antibody responses to other epitopes. We conclude that normally there is an inability to generate IgG autoantibodies to the cross-reactive (mimicking) epitope of the p542 host protein, but that this inability is overcome in a proportion of patients with autoimmune disease. We conclude also that non-cross-reactive autoepitopes exist on p542 protein, to which IgG autoantibodies can commonly be formed in autoimmune disorders. The mechanisms responsible for the latter must involve different mechanisms than those responsible for autoantibodies to the mimicking epitope.