Effect of tumor growth on the blastogenic response of splenocytes: a role of macrophage-derived nitric oxide.

In vivo growth of Dalton's lymphoma (DL), a spontaneous T cell lymphoma, has been found to increase the count of peripheral blood leukocytes (PBL). However, bone marrow cell proliferation and differentiation remained unaffected (A. Kumar and S.M. Singh, Immunol. Cell Biol., 73, 220-225). The present investigations were undertaken to study the effect of DL growth on the blastogenic response of splenocytes. A decrease in the wet weight of the spleen and in the count of splenocytes was observed at the early DL-bearing stage which, however, increased through the mid and late stages of the tumor growth. In vitro, the blastogenic response of the splenocytes of DL-bearing mice to phytohemagglutinin (PHA) was low at the early stage of the tumor, and subsequently increased at the mid and late stages. Macrophage-derived nitric oxide (NO) was found to be involved in regulating the blastogenic response of the splenocytes. DL cells are thus shown to influence splenocyte blastogenesis by altering the NO production of splenic macrophages.