| Abstract: | These experiments deal with a subpopulation of T cells bearing adsorbed Ig, thus considered to be Fc-receptor positive. Such cells were collected from spleens of lethally irradiated mice reconstituted with thymocytes 6 h after priming with heterologous erythrocytes (sheep or horse red blood cells). The helper cell function of such cells was examined upon transfer to secondary hosts with normal bone marrow cells. Such educated thymocytes upon challenge generated a 2–3-fold increase of 19 S plaque-forming cells (PFC) and a 6–7-fold increase of 7 S PFC above the level given by unprimed thymocytes. Such amplification of antibody formation is highly specific. No helper cell function was detected in cells obtained similarly from nonreconstituted animals or from mice reconstituted with bone marrow cells. Carrier-primed thymocytes collected 6 h after priming are also able to enhance the primary 7 S anti-hapten response but only when the hapten is provided on the same carrier used for priming. The helper cell function of 6 h primed thymocytes was compared to that of more conventionally educated thymocytes collected 5 days after priming. Although both cell preparations induced similar enhancements of 19 S PFC, the 6 h primed cells gave more than twice the number of 7 S PFC as compared to 5 day primed cells. This difference is statistically highly significant (p < 0.001). Since the 6 h primed thymocytes contain a subpopulation which has acquired surface Ig, as shown by our previous work, their role in the mechanism of the enhancement of the helper cell function is discussed. |
