Studies on the cellular site of action of macrophage RNA-antigen complexes.

Nonadherent spleen cell populations exposed in vitro to ribonucleic acid-rich preparations from mouse macrophages that had been incubated with human γ-globulin (RNA : HGG) were able to produce specific antibody, as measured by rosette-forming cells, in lethally irradiated (800 R), reconstituted, syngeneic mice. Exposure of the RNA to anti-HGG serum abrogated its ability to initiate antibody synthesis, as did monospecific anti-human γ chain and anti-human κ chain serum. Normal rabbit serum, anti-bovine albumin serum, anti-human μ chain or anti-human λ chain serum, when substituted for anti-HGG serum had no effect. Thus, the presence of both γ heavy chains and κ light chains of the antigen in the RNA moiety was indicated. Although both an adherent and a nonadherent cell were required by HGG to stimulate rosetteforming cells in irradiated mice, the need for the adherent cell was eliminated when RNA : HGG was substituted for HGG. In addition, anti-θ-treated bone marrow cells exposed to the RNA : HGG were capable of rosette-cell formation, suggesting that RNA attachment converted a T cell-dependent antigen to a T cell-independent antigen.