Autocytotoxic cells against normal leucocytes identified in mouse mesenteric lymphnodes

Plaques were formed in monolayers of leucocytes prepared from mesenteric lymphnodes (LN) of normal mice. The plaques were first detected after 2 h incubation, followed by a sudden increase in number at 7 h, and reached a peak between 11 and 21 h. Large cells were observed in almost all plaques under the microscope. The large cells attached surrounding leucocytes via cytoplasmic extensions, and held aggregated leucocytes on their cell surface. Aggregated leucocytes were lyzed and/or phagocytized by the large cells. Results suggest that plaque formation was due to the direct, indiscriminate killing of normal leucocytes by the large cells. The large cells increased with age. The large cells were contained in the adherent cell fraction but not the non-adherent fraction, and were removed from leucocytes by the carbonyl iron method. Thus, the large effector cells may be related to macrophages.