Mitogen and mixed lymphocyte culture responses of isolated bovine lymphocyte subpopulations

Examinations were made of the mitogen and mixed lymphocyte culture (MLC) responses of subpopulations of bovine lymphocytes isolated by density sedimentation following sequential E-rosetting with aminoethylisothiouronium bromide- and neuraminidase-treated sheep erythrocytes (EAET, EN). These procedures consistently separated 3 populations of E-rosetting T cells from a 4th population of non-E-rosetting cells (B and null cells). The isolated B and null cell population did not respond to phytohemagglutinin, concanavalin A, or pokeweed mitogen and responded minimally in mixed lymphocyte culture. Conversely, isolated T cells responded well to each of these stimuli. Moreover, differences in responsiveness were found among the 3 T-cell populations isolate by differential rosetting. T cells with receptors for both EAET and EN rosette formation were the most responsive to the mitogens used and demonstrated maximum activity in MLC. T cells with only EAET receptors had equivalent activity in MLC and less activity in response to mitogens. Cells with only EN receptors were the least active T-cell population in these assays. The different reactivities of these T-cell populations in lymphoproliferative assays indicated that they represent distinct subsets of bovine T cells.