The appearance of eosinophil-directed chemotactic inhibitory factor in the serum of complete Freund's adjuvant-treated guinea pigs.

When guinea pigs were treated by complete Freund's adjuvant (CFA), eosinophil-directed chemotactic inhibitory factor (ECIF) appeared in the serum of the treated animals. The inhibition of the response of eosinophils by ECIF was selective for the T cell-derived chemotactic factor, which has been isolated from DNP-ascaris extract-induced skin lesions (termed delayed ECF-a) but not for another ECF (termed delayed ECF-b), which was also isolated from the same skin lesions. ECIF was detected in the serum after a single CFA injection, and no significant increase of ECIF activity was observed in the serum of animals injected with CFA twice. The ECIF activity in the serum was associated with fractions of MW 70,000 and 12,500, and failed to bind to Con A-Sepharose. Furthermore, ECIF was absorbed by eosinophils but not by macrophages suggesting that eosinophils have receptor sites for ECIF. On the other hand, chemotactic inhibitor against delayed ECF-b was not detected in the serum. It was thus suggested that inhibition of eosinophil reaction by CFA treatment is related to ECIF, inhibition being selective for the eosinophil response to delayed ECF-a.