Immunorestoration of old mice by injection of thymus extract: Enhancement of T cell-T cell cooperation in the in vitro antibody response☆

Abstract The effect of injecting a thymus extract (TP-1 or Thy-5) into immunodeficient old mice on the in vitro antibody response of their spleen cells was investigated by techniques suitable for dissecting out T- and B-cell reactivities. The anti-TNP antibody response of HRBC-primed spleen cells from old mice uninjected or injected with TP-1 or Thy-5 was elicited in vitro by TNP-HRBC or TNP-Ficoll. Treatment with TP-1 or Thy-5 was found to induce only a slight increase in the anti-TNP antibody response to both immunogens. The helper activity of HRBC-primed spleen cells from untreated or treated old mice was titrated by adding graded numbers of these primed cells to cultures containing a constant number of normal spleen cells from young mice and the immunogen TNP-HRBC. Under these conditions it was found that both thymus extracts are very effective in restoring T cell-T cell cooperation in the generation of helper cell activity.