Plaque-Forming Cells of Two Different Origins in Single Hemolytic Foci

Abstract

When small numbers of spleen cells and heterologous red blood cells as antigens are injected into lethally irradiated mice, regions of hemolytic antibody-forming cell activity—hemolytic foci—can be detected in the spleens of these recipient mice. It has been shown that the number of hemolytic foci in a recipient spleen is directly proportional to the number of cells injected (1, 2), suggesting that each focus represents a single clone of antibody-forming cells, i.e., plaque-forming cells arising from one precursor cell only. Recent observations indicate, however, that formation of hemolytic foci may depend on interaction between at least two cell types. Claman et al. (3) showed that the spleens of irradiated mice injected with sheep red blood cells (SRBC) and either bone marrow or thymus cells did not develop hemolytic foci but that foci were seen when mice were injected with both cell types.