Bovine costimulator. II. Generation and maintenance of a bovine costimulator-dependent bovine lymphoblastoid cell line.

Bovine peripheral blood leukocytes, activated with concanavalin A, were cultured in bovine costimulator-containing conditioned medium prepared in a totally defined, serum-free medium. A population of leukocytes subsequently grew exponentially. These bovine cells had the morphology of lymphoblasts, were negative for chloroacetate esterase, slightly positive for conspecific esterases, and highly peanut agglutinin-positive. These data suggested that the bovine leukocytes were of the T-cell lineage and that the active factor in the costimulator-containing conditioned medium might be the bovine equivalent of interleukin 2. A quantitative microassay, subsequently developed, revealed that the lymphoblastoid cell line was costimulator-dependent and lectin-independent. Further utilization of the microassay supported this contention and strengthened the concept of a bovine interleukin 2-dependent bovine T-cell line: Phytohemagglutin-M, phytohemagglutinin-P, and concanavalin A induced active factor from peripheral blood leukocytes, while lipopolysaccharide, a potent inducer of Interleukin 1 in other systems, failed to induce activity; and both T-cells and macrophages were required for optimal factor activity. Finally, a means by which to optimize production of the active moiety, utilizing lymph node cells, as opposed to peripheral blood leukocytes, was examined.