The effects of dialyzable products from human leukocyte extracts on cutaneous delayed-hypersensitivity response.

Fractions from human whole leukocyte lysates were prepared by sequential double dialysis against membranes with cut-offs of m.w. 12,000 and 3500, and by elution chromatography on Sephadex G-10. The effect of localized intracutaneous implantation of fractions with m.w. less than 3500 was studied. Two types of response were obtained: 1) the amplification of response to antigen to which the donor had preexisting immunity, and 2) the induction of inflammatory response histologically resembling delayed hypersensitivity in the absence of added antigen. The substances mediating these responses could be separated into unique components by use of a long (1 x 150 cm) G-10 column, or by hydroxylapatite chromatography. The active principles were derived from leukocyte extracts (as demonstrated by their absence from autologous RBC extracts prepared by identical methodology), and the histopathologic appearances after intracutaneous implantation were compatible with those of a delayed-hypersensitivity response. No evidence of transfer of antigen-specific information from a sensitive donor to a nonsensitive recipient was obtained under the conditions of study.