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