Antigen-specific suppression of delayed type hypersensitivity to murine cytomegalovirus in MCMV-infected mice.

When primary infection with murine cytomegalovirus (MCMV) was by the intravenous route, the resulting delayed type hypersensitivity (DTH) to MCMV was reduced compared with subcutaneous or intraperitoneal infection. Intravenous injection of 10(3) or more p.f.u. of MCMV also reduced the DTH response to virus injected at the same time subcutaneously. When spleen cells from mice injected intravenously with MCMV 1 to 3 weeks earlier were transferred to subcutaneously infected mice, the resulting DTH response was suppressed. The cells responsible were T cells, being non-adherent and Thy-1 positive; they were not destroyed by complement plus antibody to either Lyt-1 or Lyt-2. Suppression was not transferred by serum. The suppression was antigen-specific; DTH responses induced by sheep red blood cells and by a thymidine kinase-negative strain of herpes simplex virus type 1 were not significantly suppressed by concurrent intravenous infection with MCMV. Suppression of DTH to MCMV caused by intravenously injected MCMV was reduced in mice given 50 mg/kg cyclophosphamide, but not in those given 200 mg/kg. Deoxyguanosine had no effect on the induction of DTH to MCMV.