Specific Restoration of Delayed Hypersensitivity by Lymphoid Tissue Extracts

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Abstract
Mice lose demonstrable delayed hypersensitivity (DH) to DNFB, picryl chloride, or sheep red blood cells. Reconstitution of immune responsiveness can be accomplished by administration of cell-free lysates of spleens from mice with active DH to structurally related, but not to unrelated antigens. Peritoneal exudate cell lysates from mice with active DNFB-DH also restore DH to this antigen. Sera from sensitized mice, and sera and lymphoid tissue extracts from unsensitized mice are without activity. The restorative property of splenic lysates from DNFB-sensitized mice is unstable at 56°C, not sedimented at 90,000 × G and inactivated by trypsin or magnesium ions. The presence of unexpressed, restorable DH may provide a biologic basis for the so called “transfer factor” phenomenon.