Surface antigens, SBU-T4 and SBU-T8, of sheep T lymphocyte subsets defined by monoclonal antibodies.

Monoclonal antibodies have been used to characterize molecules found on the surfaces of T cells of sheep. SBU-T4 and STU-T8 are present on 80-85% of thymocytes, absent from B lymphocytes, and present on two-thirds and one-third of lymph node T lymphocytes, respectively. Double-labelling of T lymphocytes shows that the populations recognized are mutually exclusive. Immunoprecipitation of the SBU-T4 antigen from thymocytes and T lymphocytes reveals a molecule which migrates on SDS-PAGE as a single band of 56,000 MW under both reducing and non-reducing conditions. Under reducing conditions, the SBU-T8 molecule migrates as two bands of 33,000 and 36,000 MW when immunoprecipitated from thymocytes, but only the higher MW band is present following immunoprecipitation from peripheral lymphocytes. Under non-reducing conditions, SBU-T8 migrates as dimers and other multiples. Based on immunofluorescent, immunochemical and immunohistological data, these molecules are considered to be the structural analogues of the marker molecules used to delineate T-helper and T-cytotoxic/suppressor lymphocyte subsets of other species.