Differences in thymus-dependency among various T-cell functions.

Effects of thymectomy of various times after birth on cytotoxicity, delayed footpad reaction and antibody production were examined in 6 week old mice immunized intraperitoneally with chicken erythrocytes. Cytotoxicity and antibody production were abolished by thymectomy within 3 days after birth. Mice thymectomized at 5 days of age or later showed appreciable degrees of cytotoxicity and antibody production. On the other hand, a delayed footpad reaction could be elicited even in mice thymetocmized within 24 h after birth, although the degree of the reaction was reduced by such a treatment. Therefore, T cells responsible for delayed hypersensitivity were less thymus-dependent and required the presence of the thymus for a shorter period in their development that those responsible for cytotoxicity or antibody production.