Two molecularly independent surface receptors identify bovine T lymphocytes

E rosette formation is a commonly used technique to identify T lymphocytes in many species; however, treatment of bovine E rosettes with rhodamine-conjugated F(ab')2 anti-immunoglobulin resulted in 10% (range 3-18%) of these cells exhibiting fluorescence. The failure of E rosettes to identify only non-immunoglobulin bearing cells suggested that an alternative method for T lymphocyte identification was essential. Using a labeled heterologous T cell antiserum and peanut agglutinin (PNA), identical populations of bovine T lymphocytes were identified. Unique and molecularly independent cell surface receptors were detected by dual fluorescent staining experiments differential inhibition of cellular binding of PNA by its carbohydrate ligand and capping experiments. Moreover, both reagents bound to approximately 62% of peripheral blood lymphocytes (PBLs) and virtually all thymocytes. Use of either T cell reagent in combination with rhodamine-conjugated F(ab')2 anti-bovine immunoglobulin provided a rapid, simple and reliable method for simultaneous enumeration of bovine T and B cells and permitted the detection of rare cells (less than 1%) expressing both T and B cell markers. Approximately 90% of all PBLs were identified as either T or B cells.