ANALYSIS OF PERFORIN EXPRESSION IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTES, CD-56-KILLER-CELL SUBSETS AND ITS INDUCTION BY INTERLEUKIN-2( NATURAL)

In this study new evidence is obtained by the use of an anti human per forin monoclonal antibody (mAb), anti P1, concerning the number of per forin positive cells in human peripheral blood lymphocytes (PBL). It i s shown that about 23% of PBL is perforin postive and that this percen t increases by the treatment in RPMI 1640 medium alone to 33% and with 1000 U r hIL-2 to 46%. Assessment of the cytotoxicity potential of NK cells from PBL, freshly isolated and treated, against tumor cell line K562 by the standard NK cell 4-hr 51-chromium release assay, indicate s a significant enhancement in their cytotoxicity. By FACStar sorting and analysis of the CD56+ NK cell population new evidence is obtained which shows that about 25-30% of this population represents the CD56(b right+) subset, while 70-75% represents the CD56(dim+) subset. As the two subsets were shown to differ functionally they were stained with a nti P1 for the evaluation of perforin content and it was found that bo th of them are positive for perforin from 97-99%, suggesting that the functional difference is not due to perforin content. In this sense, a s NK cells are constitutively positive for perforin, the increase in t he cytotoxicity of NK cells induced by IL-2 is most likely due to the synthesis and expression of various adhesion molecules on NK cells whi ch increase their cytotoxic potential, as well as, that the detected i ncrease in the number of perforin postive cells by this lymphokine doe s not belong to NK, but to the T lymphocyte population. The data obtai ned in this study indicate the possibility of perforin detection in hu man lymphocytes by an anti human perforin mAb and the change in the nu mber of perforin positive cells after stimulation with interleukin-2.