Activation of Normal Rabbit Macrophage Monolayers by Supernatants of Antigen-Stimulated Lymphocytes

Abstract

Tuberculin- or HSA-sensitized rabbit lymph node cells, harvested at 10 to 14 days, and normal rabbit lymph node cells were incubated for 24 hr alone or in the presence of specific or heterologous antigen. The supernatants prepared from these lymph node cell cultures were added to duplicate or triplicate monolayer cultures of peritoneal macrophages from normal rabbits, each macrophage being exposed to soluble products released in vitro by 10 lymph node cells. After 24 and 48 hr of continuous exposure to the undiluted supernatants, 150 to 300 cells in each flask were scored for adherence and ameboid activity. Macrophages exposed to supernatants from mixtures of sensitized cells with specific antigen had two to five times greater numbers of ameboid cells at 24 and 48 hr than did monolayers of the same macrophages exposed to control supernatants, and twice as many cells remained adherent at 48 hr. Thus, factors released by sensitized lymphocytes cause activation of normal macrophages. It is suggested that a similar mechanism may be responsible for cell-mediated immunity in systems involving microbial antigens.