Studies on Heterologous Antilymphocyte and Antithymocyte Sera: III. Differential Effects of Rabbit anti-Mouse Sera on Splenic Lymphocytes and Macrophages

Summary The in vivo effects of rabbit antilymphocyte (ALS) and antithymocyte sera (ATS) on splenic morphology and phagocytic function were studied in BALB/c mice which had been treated with one, two or three successive intraperitoneal injections of serum. There were no discernible differences between the effects produced by ALS or ATS, although the amount of histologic alteration varied from animal to animal. The major changes included red pulp hyperplasia, decreased cellularity of the marginal zone, and lymphocyte depletion of the periarteriolar lymphoid sheath. Following immunization with sheep erythrocytes, ALS-treated mice had a decrease in the size and number of germinal centers in splenic lymphoid follicles when compared to controls. ALS-treated mice which had been injected with 3 H-thymidine had a significant increase in the amount of isotope incorporated into splenic DNA when compared to both untreated and normal rabbit serum-treated mice. These findings correlated with autoradiographs, and suggested that ALS was more potent than NRS as an in vivo mitogen. Following the injection of 125 I-labeled flagella of S. typhi , ALS-treated mice retained much less antigen in lymphoid follicles than did NRS-or untreated controls. These data suggested that ALS preferentially impaired the function of splenic dendritic macrophages.