In vitro effect of a bovine thymic extract (thymostimulin) on T-cell differentiation in cord blood lymphocytes.

Cord blood lymphocytes were isolated from 40 normal newborns. The initial 20 samples were used to determine the dose-response curve of bovine thymic extract (Thymostimulin) by the measurement of active T cells. Results showed that the active T cells increased significantly when the Thymostimulin concentration was increased to 50 ng/ml and 100 ng/ml. The remaining 20 samples were divided into three portions and preincubated either with 50 ng and 100 ng of Thymostimulin or without Thymostimulin. The total T cells, active T cells, B cells, T-cell subsets, and lymphoproliferative responses to phytohemagglutinin, concanavalin A, and pokeweed mitogen were determined. The results showed that the active T cells, total T cells, B cells, OKT4 cells, and OKT8 cells were significantly increased after Thymostimulin treatment. The lymphoproliferative responses were also significantly increased. These data strongly support our conclusion that Thymostimulin has a marked stimulating effect on human lymphocyte proliferation and differentiation.