Restoration of impaired immune functions in aging animals. II. Effect of mercaptoethanol in enhancing the reduced primary antibody responsiveness in vitro.

The enhancing effect of 2-ME on the in vitro primary antibody forming capacity of young and old spleen cells from 5 different strains and hybrids was investigated by assessing the number of antibody-forming cells in response to sheep RBC stimulation. The following results were obtained: (1) the optimum concentration of 2-ME is 5 x 10(-5) M; (2) the best time to expose cultures to 2-ME is on day 0 together with the antigen, although days 3 and 4 were equally as effective with young but not old spleen cells; (3) 2-ME can enhance slightly the time of peak antibody response, but this appears to be strain dependent; (4) in response to antigenic stimulation over a 10,000-fold range in antidgen dose, antibody response by cultures exposed to it; (5) 2-ME is comparable to, or better than, those which had been exposed to it; (5) 2-ME is effective in enhancing antibody response because it probably promotes proliferation and transformation, as well as protects dividing cells which otherwise could not survive the culture conditions; (6) the relative number of viable cells detected on the third day of culture after antigen stimulation can be used in predicting with a reasonable accuracy (pie 2, 0.94) the magnitude of peak antibody response, which is detected normally about 2 days later; (7) 2-ME enhances antibody response of young spleen cells by about 30%, but is quite variable depending upon the genetic strain, varying from a low of --20% with random bred CV1 cells to a high of 100% with inbred C57B1 cells; (8) the enhancing effect of 2-ME on old spleen cells is much more impressive, being more that 10 times greater than on young spleen cells (i.e., 500 vs. 30%), although it too is quite variable, ranging from a low of 85% with C3H cells to a high of about 1100% with C57BL cells; (9) the enhancing effect of 2-ME on limiting numbers of spleen cells is most impressive, as judged by the relative magnitude of response by limiting (3 x 10(6)) and optimum numbers (10 x 10(6)) of young and old spleen cells and by the frequency of antibody response of cultures with limiting and optimum numbers of cells exposed to 2-ME was 23 and 3 times greater than that not exposed to 2-ME, respectively; and with old spleen cells, it was 30 and 12 times greater. In terms of the frequency of antibody responding cultures with limiting numbers of young spleen cells (3 x 10(6)), 77% responded in absence of 2-ME, whereas 100% of the cultures responded in the presence of 2-ME. The effect of 2-ME on cultures containing limiting numbers of old spleen cells was much more striking, for, in contrast to only 9% of the cultures responding in the absence of 2-ME, 78% responded in the presence of 2-ME.