Capping of the lymphocyte C3 receptor and temperature-dependent loss of C3 rosettes

The percentage of mouse spleen cells rosetted by bacteria-antibody-complement complexes (BAC) was found to be temperature dependent. Maximal rosetting was observed when BAC and spleen cells were incubated in ice (0.5 degrees C), whereas less rosetting resulted from 37 degrees C incubations. When rosetted cells were incubated at 37 degrees C, cap formation was found to occur, and indirect evidence suggested that the capped bacteria were subsequently shed from the lymphocyte surface. Neither capping nor shedding occurred at 0.5 degrees C, suggesting that these phenomena were responsible for the decreased percentage of rosetted cells found after incubation at 37 degrees C. An incidental observation indicated that a second factor potentially contributing to the loss of rosetted cells at 37 degrees C was the removal of BAC from the surface of cells by phagocytes.