Role of lymphotoxin in antibody-dependent cell-mediated cytotoxicity (ADCC)

The precise mechanism by which human peripheral blood lymphocytes (PBL) lyse antibody-coated target cells in antibody-dependent cell-mediated cytotoxicity (ADCC) is unclear. Antiserum against purified human alpha-lymphotoxin (anti-LT serum) inhibited an ADCC reaction with human PBL as effector cells and antibody-coated mouse P815 mastocytoma cells as targets. This observation suggests that alpha-lymphotoxin is instrumental in the destruction of antibody-coated targets. The inhibition was not due to a cytotoxic effect of the anti-LT serum on the PBL, nor was it caused by the presence of IgG aggregates. PBL incubated with cycloheximide were still cytotoxic in the ADCC system, although to a somewhat lower degree. This finding suggests that de novo protein synthesis not essential in the cytotoxic reaction.