Corynebacterium parvum stimulation of adherent and non-adherent cytotoxic cells in mice

Two naturally occurring cytotoxic cell populations have been identified in the peritoneal cavity of mice inoculated with C. parvum (CP), and are distinguishable on the basis of target-cell reactivity and intrinsic properties. The first effector cell was non-adherent to nylon wool and glass and non-phagocytic. These cells were selectively cytotoxic to the NK-sensitive target cell line K562, and present in the peritoneal cavity of mice 2 days after treatment with 700 micrograms of CP. The second cytotoxic effector cell was adherent to nylon wool and glass, and killed EL4 lymphoma cells derived from in vivo tumour transplants; these target cells are susceptible to phagocytic cell killing, but not NK-cell cytotoxicity in short-term (4h) assays. The adherent cytotoxic population of effector cells was present 4 days after inoculation of CP. In vivo studies showed that CP injected i.p. induced resistance to i.p. challenge with lymphoma EL4 cells, but no resistance was evident when the challenge dose was administered s.c. Adoptive-transfer studies showed that the effector cell type responsible for inhibiting tumour growth was nylon-wool adherent, probably CP-activated macrophages.