The effect of thymectomy on the genetically controlled murine immune response-1 (Ir-1) to the synthetic polypeptide poly-L(Tyr, Glu)-poly-D, L-Ala--poly-L-Lys [(T, G)-A--L] was studied with both aqueous and adjuvant immunization regimens. Adult thymectomy (combined with irradiation and bone marrow transfusion) did not affect the aqueous antigen-induced (IgM) primary response of either high or low responder mice, but did ablate the (IgG) secondary or tertiary response, a response which is restricted to the high responder strains. Adult thymectomy also blocked the normal high response to (T,G)-A--L in Freund's adjuvant in high responder mice and the high response to methylated bovine serum albumin (MBSA)-(T,G)-A--L in low responder mice. Neonatal thymectomy was also effective in blocking the response to (T, G)-A--L in Freund's adjuvant in high responder mice.

These data are consistent with the concept that the Ir-1 gene effect is mediated via thymus cell interaction with antigen and with "B"-cells during the time of induction of IgG antibody formation.

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