IN VITRO STUDY OF AN ENDOGENOUS IMMUNOSUPPRESSOR FACTOR DERIVED FROM HUMAN OR BOVINE SERUM

The effects of the human and bovine LSF (derived from sera) as well as their purified fractions were studied on murine lymphocytes reactions indicated by blast transformation (BT) assay, mixed lymphocyte culture (MLC) and IgG synthesis. The results indicated that bovine lipid suppressor factor (LSF) has significant immunosuppressive activity on lymphocytes proliferation both in BT and MLC assays. However, human LSF showed suppressive activity on lymphocyte proliferations only in MLC but not in BT assays. Concerning the effects of partially purified bovine LSF molecules on humoral immune response, we found that band #3 at 1:s dilution strongly suppresses IgG synthesis of murine spleenocytes in response to pokeweed mitogen stimulation. Band #1 and band #3 are agents with cellular immunosuppressor activity. However, band #2 is not as suppressive as the other bands in BT, MLC, and IgG assays. It seems that the mixture of all bands together may have synergistic activity in the in vitro studies. This idea has been concluded from the results in BT and MLC assays which are presented in histograms #1 and #2. Before concluding that we have found an alternative immunotherapeutic agent to cyclosporine A, we need to study the molecular structure of these compounds as well as in vivo reactions of bovine LSF in skin transplantation. Since purified human LSF and its three bands did not indicate as much cellular immunosuppressive activity as bovine LSF, the study of their effects was not followed up in detail like bovine LSF in this project