INCREASE IN TUMOR-NECROSIS-FACTOR-ALPHA MESSENGER-RNA BUT NOT PERFORIN MESSENGER-RNA EXPRESSION IN RESPONSE TO 2 NEWLY CHARACTERIZED ANTI-LFA-1 MONOCLONAL-ANTIBODIES

We have generated two monoclonal antibodies (mAb), designated anti-1B1 1 and anti-4F9, directed to the human lymphocyte-function-associated a ntigen-1 (LFA-1). Indirect immuno-fluorescence with both mAb showed a bimodal distribution of antigen on the surface of T, natural killer (N K), and lymphokine-activated killer (LAK) cells. Neither mAb reacted w ith the epitopes recognized by TAI and Mo-1 mAb on the alpha-chain of the heterodimer. Anti-1B11 and anti-4F9 immunoprecipitated polypeptide chains with molecular weights of 177 and 95 kD. Both mAb inhibited cy tolytic T lymphocytes (CTL), NK, and LAK cell-mediated cytotoxicity wi thout affecting antibody-dependent cellular cytotoxicity (ADCC). The p roliferative responses of T cells to allogeneic cells were inhibited b y anti-1B11 and anti-4F9, whereas the responses to phytohemagglutinin P and concanavalin A were not affected. Anti-1B11 and anti-4F9 blocked effector cell (EC)-target cell (TC) conjugate formation by 50%. Only anti-4F9 cross-reacted with LFA-1 on porcine peripheral blood lymphocy tes and inhibited porcine NK, LAK, and ADCC activities. Because LFA-1 also functions at the level of signal transduction during T cell activ ation and we previously showed that CTL rapidly degraded perforin and tumor necrosis factor-alpha (TNF alpha) mRNA after interaction with se nsitive TC, we examined the effects of the mAb on the messages for per forin and TNF alpha. Treatment of CTL with anti-1B11 and anti-4F9 indu ced TNF alpha message and protein levels of TNF alpha, but did not alt er perforin mRNA levels.