Thymus-derived lymphocytes control the expression of immunogenic properties of peritoneal macrophages.

Macrophages, given keyhole limpet hemocyanin in vitro, from normal mice initiate in culture antigen-specific T cell-mediated immune reactions. On the other hand, macrophages from nude, from adult-thymectomized, or from neonatal-thymectomized mice are impaired with respect to their capacity to signal such an antigen-specific T cell reaction. Thymocytes from hydrocortisone-treated donors, added in culture to such impaired macrophages, rendered them immunologically potent. The capacity of macrophages from adult thymectomized mice to promote the activation of antigen-specific "helper" T cells which, cooperating with B lymphocytes, would lead to antibody production, was also impaired. Thus, it appears that short-lived T lymphocytes control the maturation of macrophages up to a stage at which they can present antigen-specific T cells with antigen in an immunogenic form. We found that such T lymphocytes also control the phagocytic properties of macrophages, yet the impairment of their immunogenic properties does not seem to be derived from decreased phagocytosis.