In vitro assessment of cellular immunity to vaccinia virus: contribution of lymphocytes and macrophages.

The possible contributions of lymphocytes and macrophages to immunity to vaccinia virus were examined in vitro by determination of antigen-specific inhibition of migration of macrophages and the replication of the virus in purified macrophages. Lymphocytes from various anatomic sites of vaccinia virus-immune rabbits mixed with macrophages from nonimmune rabbits resulted in antigen-specific inhibition of macrophage migration; purified lymphocytes of peritoneal exudates were found to be the most potent inhibitors. Macrophages from peritoneal exudates of immune rabbits purified to contain less than 1% lymphocytes were sensitive to inhibition of migration by vaccinia antigens. Virus grew in macrophages from nonimmune rabbits, but failed to replicate in macrophages from the peritoneal cavity of immune rabbits. Alveolar maracrophages from immune rabbits were not inhibited from migrating in the presence of the viral antigen, and the virus replicated in these cells. The data suggest, but do not prove, that cellular immunity to vaccinia virus in rabbits may be mediated both by lymphocytes and by macrophages.