Effect of serum on lymphocyte blastogenesis. 2. Characterization of disease-induced immunosuppressive factors by chromatography and molecular weight determination.

Numerous infectious and noninfectious diseases are associated with the appearance of suppressive serum lymphocyte immunoregulatory factors (SLIFs). The suppressive SLIFs in sera from clinically healthy dogs and from dogs with bacterial (staphylococcal, brucellar) or mycotic (blastomycotic) infections were further characterized by dialysis, fractionation by ultrafiltrations and HPLC (high performance liquid chromatography) sieving, by affinity chromatography on protein A-Sepharose columns, and by DEAE-cellulose ion exchange chromatography. Factors of various molecular weights and of various elution patterns from DEAE-cellulose and affinity chromatography columns were taking part in the suppressive action of the whole serum. The 'common' inhibitors present in all sera were in the molecular weight range of 28 to 35 Kd, whereas the disease-induced suppressive SLIFs were present in various molecular weight categories. 'Common' suppressor SLIFs and some SLIFs from dogs with staphylococcal infections were partially dialysable; suppressive SLIFs induced in dogs with generalized brucellosis and blastomycosis were not dialysable. Protein A bound suppressive SLIFs from two of three dogs with staphylococcal pyodermas. DEAE-cellulose chromatography gave variable elution patterns with different animal sera. It is concluded that various suppressive SLIFs contribute to the immunosuppressive effect of the whole serum and no disease-specific suppressive SLIF could be identified.