Understanding the mechanism of action of bacterial superantigens from a decade of research

In the face of the unique diversity and plasticity of the immune system pat hogenic organisms have developed multiple mechanisms in adaptation to their hosts, including the expression of a particular class of molecules called superantigens. Bacterial superantigens are the most potent stimulators of T cells. The functional consequences of the expression of superantigens by b acteria can be extended not only to T lymphocytes, but also to B lymphocyte s and to cells of the myeloid compartment, including antigen-presenting cel ls and phagocytes. The biological effects of bacterial superantigens as wel l as their molecular aspects have now been studied for a decade. Although t here is still a long way to go to clearly understand the role these molecul es play in the establishment of disease, recently acquired knowledge of the ir biochemistry now offers unique experimental opportunities in defining th e molecular rules of T-cell activation. Here, we present some of the most r ecent functional and molecular aspects of the interaction of bacterial supe rantigens with MHC class II molecules and the T-cell receptor.