DIRECT ANTIMICROBIAL ACTIVITY OF T-CELLS

T cells are generally thought to contribute to antimicrobial activity either by releasing lymphokines, which recruit and activate other cell types, or by major histocompatibility complex (MHC)-restricted lysis of infected host cells. Recently, it has become apparent that T cells can also mediate antimicrobial activity by direct interaction with mic robial targets. Such interactions, which can be either antigen specifi c or nonspecific, occur in the apparent absence of MHC restriction and do not require the presence of other host cells. Microbial targets re cognized by T cells include fungi, parasites and bacteria. Here, Stuar t Levitz, Herbert Mathews and Juneann Murphy discuss the direct antimi crobial activity of T cells and speculate on its in vivo relevance.