Dialysable Leukocyte Extracts (Transfer Factor) Augment Nonspecifically Keyhole Limpet Haemocyanin and Horseshoe Crab Haemocyanin Skin Reactivity in Unimmunized Human Recipients

Dialysable leukocyte extracts (DLE) may induce marked changes in the immune expression of human recipients. It is unclear whether the conversion of skin reactivity by DLE is due to a donor‐related specific transfer factor or to an antigen nonspecific augmenting factor which enhances a preexisting low‐level response in DLE recipients. In this study, DLE from immunized and unimmunized human and calf donors or saline was administered to 88 medical students. The recipient population demonstrated minimal background responses to the test antigens keyhole limpet haemocyanin (KLH) and horseshoe crab haemocyanin (HCH). The results indicate that the DLE preparations from both immunized and unimmunized donors significantly stimulated skin reactivity but not in vitro responses to both KLH and HCH in the recipient population. The results suggest that these DLE preparations contain an immunologically nonspecific augmentor, which stimulates a preexisting low‐level response in the unimmunized population to become a clearly observable skin reaction.