Influence of tumour carriage on the production of lymphokines affecting macrophage behaviour.

Normal and cyclophosphamide (Cy)-enhanced delayed-type hypersensitivity (DTH) reactions to sheep red blood cells (SRBC) were severely impaired in CD1 mice injected with 10(6) viable Landschutz ascites carcinoma (LAC) cells at the time of immunization. The tumour-induced suppression of DTH was accompanied by inhibition of splenic T-lymphocyte responses to antigen and mitogen. This was assessed by measuring lymphocyte transformation and the production of two lymphokines affecting macrophage behavior, i.e. lymphocyte-derived chemotactic factor (LDCF) and macrophage procoagulant-inducing factor (MPIF). Our results imply that impaired production/function of lymphokines affecting macrophage behaviour may play a key role in tumour-induced suppression of cell-mediated immunity and that this inhibition is independent of Cy-sensitive suppressor cells.