Superantigens and Microbial Pathogenesis

The results of a randomized, controlled trial of endoscopic ligation of esophageal varices compared with sclerotherapy by Laine and colleagues, in this issue of Annals, is the second report of a relatively new endoscopic technique. The two techniques appear to be approximately comparable, except that the complication rate is less with ligation. Whether ligation will replace sclerotherapy remains to be seen.

Recent analysis of various bacterial and viral products has revealed that microbial proteins may be not only responsible for microbial infection and disease but also connected to the onset of autoimmunity. These microbial products are called superantigens because of their strong effect on the proliferation of certain T-lymphocyte populations. Superantigens elicit various biological activities, including lymphocyte mitogenesis, pyrogenicity, depressed antibody production, and shock [1, 2]. We describe the effects of microbial superantigens on immune function and their possible association with various acute and chronic inflammatory diseases.

T cells mediate protection against infectious agents by producing lymphokines after activation by specific antigens. Lymphokines affect the function of other cell types, including phagocytic cells, involved in antimicrobial immunity. Most mature T cells express receptors (T-cell receptors) composed of and chains, which are necessary for the specific recognition of antigens [3]. Both and chains consist of constant and variable (V) regions. Many V and V families of genes can encode the V regions of T-cell receptors; however, the antigen receptor of a single T cell is encoded by only a single V and V family member.

T-cell receptors only recognize antigens when the antigens are bound in the groove of major histocompatibility complex class II molecules. These class II molecules are expressed on the surface …