Murine transfer factor. IV. Studies with genetically regulated immune responses

Transfer factor--current status and future prospects

We have detected new clues to the composition and function of "Transfer Factor" using the direct Leucocyte Migration Inhibition (LMI) test as an in vitro assay of Dialysates of Leucocyte Extracts (DLE). This approach has revealed two opposing antigen-specific activities to be present in the same > 3500 < 12,000 DA dialysis fraction - one activity is possessed of Inducer/Helper function (Inducer Factor). The opposing activity is possessed of Suppressor function (Suppressor Factor). When non-immune leucocyte populations are cultured with Inducer Factor they acquire the capacity to respond to specific antigen and inhibition of migration occurs. This conversion to reactivity is antigen-specific and dose-dependent. When immune leucocyte populations are cultured with Suppressor Factor their response to specific antigen is blocked and Inhibition of Migration is prevented.

Structural nature and functions of transfer factors

Transfer factors are molecules that "educate" recipients to express cell-mediated immunity. This effect is antigen-specific. The most consistent effects of transfer factors on the immune system are expression of delayed-type hypersensitivity and production of lymphokines such as macrophage migration inhibitory factor (MIF), which is probably identical to gamma-interferon in response to exposure to antigen. Transfer factors bind to antigens in an immunologically specific manner. This discovery has enabled us to isolate individual transfer factors from mixtures that contain several transfer factors. This reactivity probably explains the specificity of individual transfer factors, and it has provided a method for purification of individual transfer factors to apparent homogeneity. The purified materials are immunologically active and antigen-specific. They have molecular weights of approximately 5,000 Da and appear to be composed entirely of amino acids. Transfer factors appear to offer a novel means of molecular immunotherapy for certain patients with defective cell-mediated immunity.

Purification of transfer factors

Transfer factor activities have been studied in both clinical and basic science settings for several decades. Until now, highly purified transfer factors that are suitable for molecular analysis have not been available. This has impeded progress towards understanding the molecular and cellular basis of the activities of these important inducers of cell-mediated immune responses. Murine transfer factors with specificities for chicken egg albumin or horse spleen ferritin were purified to virtual homogeneity using a combination of affinity chromatography and reversed-phase and polytypic high performance liquid chromatography (hplc). Transfer factors prepared by this methodology were recovered in high yield and in biologically-active, antigen-specific forms. The purified materials were further analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis, chromatographic methods and an in vivo assay for immunological activity. For the first time definitions for unit transfer factor activity and specific activity are introduced. The results of these experiments indicate that transfer factors are a family of highly polar, hydrophilic molecules of low molecular weight (approximately 5,000) which are produced in small quantities by lymphoid cells and which have potent biological activity. The availability of purified transfer factors should facilitate definitive studies into the nature and mechanisms of production and action of these molecules.