CHARACTERIZATION OF A NON-GRANULE ASSOCIATED PORE-FORMING PROTEIN IN AGRANULAR LYMPHOCYTES

Recently, two populations of small lymphocytes (SL) have exhibited non -major histocompatibility complex (MHC) restricted lysis, Recent studi es by numerous laboratories have demonstrated that resting T cells tri ggered through CD3 and CD28 costimulations can result in immediate, no n-MHC restricted killing, Our recent studies with CD3(-), CD56(+) SL d emonstrated that although these cells contained no cytoplasmic granule s detected with electron microscopy, they mediated potent NK and ADCC activity, In the present study, we have used a Western blotting techni que that allows for the detection and quantitation of total cellular l evels of pore-forming protein (PEP), We have found that freshly isolat ed peripheral non-granulated lymphocytes (both CD3(+) and CD3(-)) cont ain PFP. In addition, CD3(-), CD56(+) SL contain levels of PFP similar to those of the highly granular CD3(-) LGL. In search of non-ganule P FP, we exploited the rat NK (RNK) cell lines as a source of other pote ntial cytotoxic factors, A membrane associated PFP, based on Western b lotting, was isolated from rat RNK cells, Unlike PFP isolated from gra nules, this PFP was active after culture in Ca2+-containing medium. Ho wever, the lytic activity isolated from the non-granule PFP of RNK cel ls was inhibited by monoclonal antibodies to PFP, Collectively, these studies indicate that PFP is present in small agranular lymphocytes (b oth NK and T cells) and that it is not stored in large cytoplasmic gra nules, The implication of our results for the acquisition and activati on of lytic ability in NK and T cells will be discussed.