ROLE OF FUNCTION-ASSOCIATED MOLECULES IN TARGET-CELL LYSIS - ANALYSISOF RAT ADHERENT LYMPHOKINE-ACTIVATED KILLER-CELLS

Monoclonal antibodies (MAbs) against fish nonspecific cytotoxic cells (NCC) inhibit the lysis of target cells by NCC and by human and rat na tural killer (NK) cells. We now show that the anti-function-associated molecule (anti-FAM) MAb 5C6 also inhibits the cytolytic activity of r at (F344) nonadherent lymphokine-activated killer (LAK) cells and adhe rent LAK (ALAK) cells. Rat nylon-wool-nonadherent (NWNA) cells were cu ltured for 48 h in recombinant human interleukin-2 (IL-2). Nonadherent cells were then removed and the plastic-adherent (ALAK) cells were re cultured for 9 days. Cells were daily analyzed by cytometry (using MAb 5C6 and the rat NK cell MAb 3.2.3) and cytotoxicity. Approximately 40 % of the initially cultured NWNA cells, 50-60% of the LAK cells and 87 -98% of the ALAK cells were positive for MAb 5C6. Tissue culture super natants containing MAb 5C6 caused a dose-dependent inhibition of cytot oxicity against P815 and YAC-1 targets. Approximately 50% inhibition w as obtained at MAb concentrations of 1.25-2.5 mug/ml. Maximum inhibiti on of ALAK cytotoxicity was 86% on day 4 of culture. Two-dimensional S DS-PAGE and Western blot analysis of acetone-precipitated cell membran e preparations identified a 55-kD molecule (pI 6.1-6.3) on NWNA and AL AK cells and an additional slightly more acidic 45-kD protein on ALAK cells. These data indicate that rat ALAK cells may initiate lysis of t arget cells via receptor binding.