Adherent spleen cells from mice acutely infected with cytomegalovirus suppress the primary antibody response in vitro.

In the present study, we have demonstrated that the hemolytic plaque response of spleen cells from mice acutely infected with murine cytomegalovirus (MCMV) is suppressed in vitro. Mishell-Dutton cultures established with spleen cells from C57BL/6 mice infected 4 days earlier with 4.2 X 10(3) plaque-forming units of MCMV were found to produce significantly fewer direct plaques upon stimulation with sheep red blood cells than corresponding control cultures. Suppression could not be attributed to a generalized lytic destruction of spleen cells, nor was it produced by addition of virus directly to uninfected spleen cell cultures. However, in cultures containing various mixtures of cells from control and infected mice, the direct plaque response was markedly below the predicted response, suggesting that the uninfected cells were actively suppressed by cells from infected mice. Suppression was dependent on the presence of intact spleen cells, since it was not found in the presence of lysed cells. The capacity of spleen cells from infected mice to mediate suppression was demonstrated in the plastic-adherent subpopulation. Treatment of these cells with anti-thymocyte serum (ATS) and complement did not abolish the capacity to suppress the immune response. Thus, adherent ATS-resistant cells from the spleens of mice acutely infected with MCMV, rather than virus alone, have the capacity to actively suppress the hemolytic plaque response in vitro.