Identification of A T lineage antigen in the catfish

A murine monoclonal antibody produced against catfish thymocytes and immunoglobulin-negative lymphocytes in the blood identified a catfish T cell antigen designated Cf T1. The Cf T1 antigen was found to be expressed on thymocytes, a subpopulation of the lymphoid cells in blood and other lympho-hemopoietic tissues, and a T cell line, but was not expressed by erythrocytes, thrombocytes, myeloid cells, B cells or macrophage cell lines. Stimulation of blood mononuclear cells with the T cell mitogen, concanavalin A, resulted in an increased frequency of Cf T1 + cells. Conversely, lipopolysaccharide stimulation increased the number of IgM + B cells and decreased the frequency of Cf T1 + cells. The Cf T1 antigen was defined as a single chain protein of M r 35 000 lacking N- and O-linked sugars. The Cf T1 molecule thus provides a T lineage-specific marker in this bony fish representative.