Abstract
It was observed that when normal mouse spleen cells were cultured alone in vitro (precultured) for 5 to 7 days, these precultured cells lost the ability to produce antibody during subsequent in vitro sensitization with antigen. These precultured cells, which were themselves unable to produce antibody, also actively suppressed the generation of antibody-forming cells from freshly cultured spleen cells. The supernatant from the precultured cells was not suppressive.
The suppressor cells inhibited both the primary and secondary antibody-formation responses. The suppression was nonspecific to both immunoglobulin class and antigen. The suppressor cells inhibited the mitogenic response of normal spleen cells to both phytohemagglutinin (PHA) and bacterial lipopolysaccharide (LPS), but the LPS-response was much more sensitive to the suppression than was the PHA-reponse. These results indicate that the target cells of the suppressor cells are both T and B cells, and the mechanism of action of the suppression is proliferation inhibition of target cells.
