Rabbit B spleen lymphocytes and macrophages as accessory cells in T-cell activation by mitogens

The enhancement of the response of T cells to concanavalin A (ConA) and phtyohaemagglutinin (PHA) by macrophages has been shown in most species, whereas the accessory role of B cells has been only described in studies using human or rabbit lymphocytes. In rabbit, the accessory activity is confined to a subpopulation of B lymphocytes: the majority of B cells have sedimentation velocity of 2.5 to 4 mm/h, whereas the maximum of the accessory activity is found among the B cells, sedimenting with a velocity of 3.5 to 8 mm/h; B cells sedimenting between 1 and 3.5 mm/h have only a very weak accessory activity. Splenic adherent and/or phagocytic spleen cells may contribute additional augmentation of the response of T cells to ConA, since other macrophages (peritoneal and alveolar) are able to increase the ConA response to spleen T cells.