Suppressor T cells and host resistance to tye 111 pneumococcus after treatment with antilymphocyte serum

The antibody response to type III pneumococcal polysaccharide (SS-II) was significantly increased in mice treated with antilymphocyte serum (ALS). BALG/c mice given 0.25 ml of ALS on days -1, 0, and 1 relative to the days of immunization with 0.5 mug of SSS-II had a 20-fold increment (11,383 increased to 199,917) in the number of splenic plaque-forming cells enumerated on day 5 compared with untreated, immunized controls. This effect has been attributed to the elimination of subpopulation of thymus-derived lymphocytes (T cells) that has suppressor function. The present series of experiments relate the augmented antibody response to SSS-II in mice treated with ALS to increased host resistance after infection with Streptococcus pneumoniae, type III (Pn-II). The 50% lethal dose of Pn-III in niminnunized mice was 102 and the 100% lethal dose was 103 organisms. Mice immunized with 0.5 mug of SSS-III and challenged 5 days later with Pn-III were completely protected against a dose of up to 108 organisms. Mice treated with 0.25 ml of ALS on days -1, 0, and 1, immunized with SSS-III on day 0, and challenged with 2.5 X 10(9) Pn-III on day 5 had a mean survival time of greater than 100 h compared with 16 h for immunized non-serum-treated ...Continue Reading