Augmentation of delayed-type hypersensitivity in antigen-primed guinea pigs by human dialyzable leukocyte extract. Chromatographic and enzymatic characterization of the active principle.

Column chromatographic purification and sensitivity towards enzymatic treatments of dialyzable transfer factor (TFd), the immunologically specific component of dialyzable leukocyte extract (DLE), have previously been used in its biochemical characterisation. In the present work we studied the effect of enzymes and the Sephadex G-10 chromatographic separation of the components of DLE augmenting delayed-type hypersensitivity. Skin reactivities to streptokinase-streptodornase (SK-SD) and tuberculin PPD were significantly augmented by injecting DLE into antigen-primed guinea pigs. The augmentation caused by DLE treatment correlated to the pre-existing level of immunity in the recipients. Most of the augmentory activity resided in 2 adjacent fractions, eluting early from a Sephadex G-10 column. This augmentation was destroyed by alkaline hydrolysis, by treatment with pronase, proteinase K, ribonuclease, and nuclease P1, but not by alkaline phosphatase or phosphodiesterase II. The observed sensitivities towards these enzymes, except that for ribonuclease, were closely similar to those described for the specific TFd component of DLE. These results are compatible with the idea that either the nonspecific augmenting and the specific TFd molecules are principally similar, or that the TFd molecules, in addition to their capacity to transfer specific immunity, also have an augmenting effect, which needs in its manifestation a sub-threshold dose of immunogen.