The immunological basis of inflammatory diseases

Most immunologically-mediated diseases are inflammatory in nature, as assessed by cellular infiltrates at the lesion site. Recent immunohistological studies using monoclonal antibodies on tissue sections and synovial or cerebrospinal fluid reveal that B- and T-lymphocytes (predominantly T) participate in this reaction, together with monocytes and macrophages. The etiopathogenesis of inflammatory diseases of immunological origin can be discussed at two levels. (1) Lesions may be secondary to the cytopathic effect of antibodies, either by direct cytolysis or by opsonization, antigenic modulation, or blockage of functionally-relevant molecules. Immune complexes formed in the circulation or locally at the lesion site may intervene. Direct cellular mechanisms are probably involved, as suggested by evidence in hepatitis (indirect) and in juvenile insulin-dependent diabetes (direct). K-cells may act by antibody-dependent cytotoxicity, particularly in autoimmune diabetes and thyroiditis where lymphocyte-dependent antibodies are demonstrated. Unfortunately, the absence of adequate markers does not permit adequate detection of K-cells in inflammatory reaction sites. (2) Etiological factors are multiple in a given disease and even in a single patient. Deficiency of suppressor T-cells, assessed using monoclonal anti T-cell antibodies, represents a major predisposing factor, although suppressor cell deficit may be restricted to some antigens (EBV) in certain patients. The deficiency of interleukin-2 production in lupus and rheumatoid arthritis is intriguing but the mechanism and its relationship to disease etiology are unknown. Other immunological factors include intrinsic B-cell hyperactivity, anti-T-cell auto-antibodies, and complement deficiencies, whereas non-immunological factors such as viruses, drugs or sex hormones are important but ill-defined.(ABSTRACT TRUNCATED AT 250 WORDS)