Characterization of chemotactic activity produced in vivo by a cell-mediated immune reaction in the guinea pig.

A system that allows repeated sampling of peritoneal fluid at various time intervals has been adapted to study mechanisms of leukocyte accumulation in vivo. Application of this technique in guinea pigs exhibiting delayed hypersensitivity (DH) to horse radish peroxidase (HRPO) has allowed characterization of some events after i.p.challenge with the sensitizing antigen. Within 24 hr of the administration of HRPO i.p. to such animals there is a significant increase in the number of peritoneal macrophages and in the chemotactic activity (CTX) for macrophages in the sampled peritoneal fluid. At 48 and 72 hr the CTX returns to the pre-challenge level and i.p. macrophages appear to be actively phagocytic. Molecular sieve chromatograms of concentrated peritoneal fluid obtained 24 hr after i.p. challenge with HRPO and of supernatants derived from immune spleen cells cultured in the presence of HRPO in the presence of HRPO in vitro revealed that the major portion of CTX for homologous macrophages eluted in the region of the 12,500 dalton protein marker. The partially purified CTX obtained from peritoneal fluid and supernatants of spleen cell cultures was heat stable (56 degrees C for 30 min) and was destroyed by trypsin digestion. These data demonstrate that a chemotactic factor (LDCF) obtained in vitro, is present in vivo at the site of a cell-mediated immune reaction. Moreover, these observations demonstrate the feasibility of studying the kinetics of leukocyte accumulation and the production of mediators of inflammation at the site of well defined immunologic reactions in vivo.