Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. III. High dose of antigen induces suppressor T cells which influence the appearance in exudates of effector T cells for delayed-type hypersensitivity and helper T cells for humoral immune responses.

Antisera produced in rabbits against adherent cells of rat alveolar or peritoneal lavage fluid (anti-rat alveolar macrophage sera, ARAMS, or anti-rat peritoneal macrophage sera, ARPMS) were used to detect antigenic differences between alveolar (AM) and peritoneal (PM) macrophages in an indirect membrane immunofluorescence (IMF) test. Of all sera tested, the IMF titres were higher with cells of that population which was used for immunization. These differences were found before and after exhaustive absorptions with insolubilized rat plasma, rat erythrocytes, and non-adherant rat kidney, spleen, thymus and bone marrow cells. The differences were not due to antigens specific for one of the macrophage populations, as demonstrated by cross-adsorption studies with macrophages of different localization. It is assumed that two or more macrophage specific antigenic determinants are present in different density in the two macrophage populations.