Angiogenic activity by spleen cell supernatants from tumor-bearing and tumor-resected mice

Supernatants of cultured spleen cells (SCS) from small tumor‐bearing mice (STBM) and large tumor‐bearing mice (LTBM) are able to enhance tumor growth as well as accelerate tumor takes in vivo when inoculated 24 h before tumor implant. After tumor resection enhancing activity disappears at a rate depending on the size of the resected tumor. Spleen cells from tumor‐bearing mice also evoke a complex vascular response, lymphocyte‐induced angiogenesis (LIA) elicited via the release of lymphokines from activated T cells. As angiogenic factors promote tumor development we investigated if SCS from tumor‐bearing and tumor‐resected mice contain factors capable of evoking a LIA response. Angiogenic activity was detected by SCS of small and large tumor‐bearing mice as well as in large tumor‐resected mice. On the other hand, SCS from small tumor‐resected mice are not able to evoke an angiogenic response. Possibly, the large antigenic burden in LTRM stimulate the immune system in a different way than in STRM. We can suggest that the different behavior of spleen cells after small and large tumor removal can be explained by quantitative or qualitative changes in the spleen subpopulations.