Guinea pigs immunized with protein antigens emulsified with complete Freund's adjuvant (CFA) and skin tested at 3-4 wk have classical tuberculin-type delayed hypersensitivity (DH) reactions with few basophils present. However, recipients of T cells from these animals have delayed responses containing large basophil infiltrates and thus resemble basophil-rich cutaneous basophil hypersensitivity (CBH) responses that are elicited in animals immunized without CFA. This suggests that animals immunized with CFA have T cells with basophil-recruiting capacity but that this activity is suppressed. Using a transfer system, we found that immune serum from donors immunized with CFA had the ability to suppress the basophil-recruiting capacity of immune T cells. When immune serum and peritoneal exudate cells from guinea pigs immunized with CFA were co-transferred intravenously to normal recipients, the cell-mediated transfer of basophil-rich responses was suppressed. The responsible serum factor was antigen nonspecific, had an approximately 70,000 mol wt, and acted preferentially on cells from donors that express basophil-poor DH responses. Thus, tuberculin-type delayed hypersensitivity and CBH might be mediated by a common T cell, but the resulting basophil component of the delayed response depends on the modulation of T cell recruitment of basophils by factors in CFA-immune serum.

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