Modulatory Effects of Splenic Accessory Cells on in Vivo Antibody Response
We have previously reported that the transfer of 2 x 106 radioresistant (r.r.) spleen cells into normal syngeneic recipients enhanced antibody response to SRBC in rats (1). Similarly, an increased PFC response to 5 x 10 SRBC was induced in BALB/c mice by the i.p. injection of 1–5 x 106 r.r. syngeneic spleen cells, at the time of immunization (2). Elimination of adherent or phagocytic cells abolished the enhancing capacity of r.r. cells suggesting that cells responsible for the observed effect were macrophages. One hour preincubation in medium containing 0.4 mg/ml, kappa-carrageenan potentiated rather than inhibited the enhancing effect of r.r. spleen cells. The transfer of r.r. cells significantly increased the number of PFC in the spleens of mice immunized with suboptimal dose (5 x 105 SRBC) but did not abrogate the suppressive effect of the supraoptimal dose of antigen (5 x 109 SRBC). In order to test whether the potentiating effect of accessory cells is dose-dependent, graded numbers of r.r. spleen cells were injected into mice immunized with 5 x 107SRBC.