Regulation of the immune response: III. The role of macrophages in the potentiation of the immune response by Fc fragments.

The Fc fragment-induced enhancement of the anti-SRBC response was found to be dependent upon the presence of functional macrophages. Fc fragments derived from human immunoglobulin were unable to enhance either the in vivo or in vitro anti-SRBC response in the C3H/HeJ mouse, whereas similar responses in histocompatible C3Heb/FeJ mice were enhanced. Macrophages were found to be required for the Fc fragment-induced adjuvant effect as evidenced by the inability of C3H/HeJ macrophages to substitute for C3Heb/FeJ macrophages in Sephadex G-10-filtered C3Heb/FeJ spleen cell cultures. Moreover, the C3H/HeJ anti-SRBC response could be enhanced when Fc subfragments were employed instead of Fc fragments. The C3H/HeJ-derived T cells were normal, since they could be added to B cells and macrophages derived from the C3Heb/FeJ mouse with an enhanced response observed in the presence of Fc fragments. The fact that C3H/HeJ macrophages function normally as accessory cells in generation of the anti-SRBC response but fail to function in the Fc-induced adjuvant effect allows the dissection of 3 macrophage functions in the modulation of the antibody response.