MECHANISMS OF CTL-MEDIATED CYTOXICITY

CTL can utilize three separate mechanisms for killing foreign or viral ly infected cells. The perforin and Fas lytic mechanisms cause rapid ( 4-6h) lysis of target cells; surface-bound TNF-alpha causes slow (18-2 4h) destruction of target cells. lit order to assess the relative cont ributions of the various lytic pathways in immune reactions thought to be based on CMC, several laboratories have generated perforin-less (P O) mice. Although such mice have intact vigorous Fas and TNF-alpha lyt ic pathways, they are unable to clear infection by LCMV. On the other hand, they are able to reject allografts. The implications of this for CTL function in vivo are discussed. (C)1996 Academic Press Ltd