THE ROLE OF GAMMA-DELTA-T-CELLS IN THE NORMAL AND DISORDERED IMMUNE-SYSTEM

A small population of T cells does not express the conventional T cell receptor characterized by the α and β polypeptide chains (TCR αβ) but instead, two polypeptides termed γ and δ (TCR γδ). This alternative receptor is able to recognize antigen. It appears early in T cell ontogeny, but its role in the thymus prior to the availability of TCR αβ remains unclear. In selected sites such as skin or gut TCR γδ predominates in mice which might suggest a role of γδ T cells in the first line of defense against infection, γδ T cells secrete lymphokines and display cytotoxic activity. However, their activation requirements may differ from what is known for αβ T cells since MHC-nonrestricted and also CD4 and CD8 negative γδ T cells have been described. Preferential activation by mycobacterial antigens possibly indicates a special repertoire of the γδ T cells. In various diseases slightly increased numbers of γδ T cells were found, but these preliminary studies have not yet provided evidence for a major pathogenetic role of γδ T cells. © 1990 Springer-Verlag.