Demonstration of two distinct macrophage specific antigenic determinants in rats.

Exhaustive cross-absorptions of rabbit anti-rat alveolar macrophage sera with peritoneal macrophages and of anti-rat peritoneal macrophage sera with alveolar macrophages did not prove the existence of antigenic determinants specific for alveolar or peritoneal macrophages. Titer-differences of these sera on RAM and RPM seem to be caused by a different distribution of two or more macrophage specific determinants present in both cell populations. Macrophages from other rat tissues show reactivity with these two sera different as well from alveolar as from peritoneal macrophages.