Level of macrophage induction during tumor growth: primed or activated?

The activation level of thioglycolate (TG)-elicited peritoneal macrophages (Mphi) from normal and fibrosarcoma-bearing BALB/c mice was investigated. Lipopolysaccharide was used to distinguish in vitro levels of Mphi activation. The results of cytotoxicity assays, which measured nonspecific killing of P815 tumor cells by activated Mphi, indicated that tumor-bearing host Mphi were primed in situ while normal host Mphi remained in a resting state. This level of Mphi induction may contribute to the resulting tumor-bearing host T cell immune hyporesponsiveness.