Studies on the differentiation of T lymphocytes in sheep I. RECOGNITION OF A SHEEP T-LYMPHOCYTE DIFFERENTIATION ANTIGEN BY A MONOCLONAL ANTIBODY T-80.

The results presented in this paper demonstrate that a mouse IgM monoclonal antibody (T-80) recognizes an antigen on cells of the T-lymphocyte lineage of sheep. However, this antibody does not identify all T cells, as 10-20% of thymocytes and some peripheral-blood T cells are negative. T-80^- thymocytes reside in the medulla. The majority of cortical thymocytes are T-80⁺ and classified as dull cells on the basis of antigen density per cell as measured by flow microfluorometry. In contrast, T-80⁺ cells in the periphery can be categorized into two populations, i.e., dull cells and bright cells. Suggestive evidence was obtained that bright T-80⁺ cells are fast recirculating T cells, whereas dull ceils are sessile or less easily mobilizable T cells in the periphery. In foetal environment, over 90% of thymocytes and approximately 5% of spleen cells are T-80⁺ at 54 days of gestation (gestation period = 150 days), which may indicate that T-cell emigration from the thymus commences well before mid-gestation in sheep. [ABSTRACT FROM AUTHOR]