L-5178-Y lymphoma associated immunosuppression in Balb/c mice.

Lymphoma L-5178-Y bearing Balb/c mice were unable to mount a delayed-type hypersensitivity reaction to dinitrofluorobenzene (DNFB). A suppressor factor present in the ascitis of these mice inhibited the response if given during DNFB sensitization, but not during challenge. The factor was not present in lymphoma-bearing Balb/c nu/nu mice. It appeared to be a 35-66 kDa protein. Non-specific esterase staining indicated that the spleens of tumor-bearing and ascitis-injected mice contained a large excess of macrophages. Our observation that the suppressor factor prevented the very start of the immune response may indicate why immunostimulation is difficult to obtain in cancer bearing hosts.