Delayed hypersensitivity. I. Effect of in vitro exposure of cells to antigen upon leukocytic transfer of delayed hypersensitivity.

Exposure to picryl guinea pig albumin with 3-6 picryl groups per mole failed to affect the ability of peritoneal exudate or peripheral blood leukocytes from sensitized donors to transfer delayed sensitivity to normal recipients. In contrast, conjugates containing 40-48 picryl groups per mole altered the ability of exposed leukocytes to transfer delayed sensitivity. Evidence is presented that highly conjugated guinea pig albumin is self-aggregating. Lightly conjugated albumin, previously heat-aggregated, also was effective in "desensitization." The properties of antigen size, cell association of antigen after exposure, and desensitization appear to be associated.