Immune modulation exerted by thymic humoral factor (THF-gamma 2), on T-cell subsets and IL-2 production of umbilical cord blood lymphocytes.

The effect of a synthetic thymic humoral factor, THF-gamma 2, on the immune competence of T-cells was investigated in vitro on lymphocytes from human cord blood (UCBL). It was found that preincubation of UCBL with THF-gamma 2 caused an increase in the percentage of cells expressing the CD4 or the CD8 differentiation antigens, but did not affect the percentage of CD3 cells. The effect of THF-gamma 2 on PHA-induced IL-2 secretion was also studied and found that a 3hr preincubation with THF-gamma 2, prior to suboptimal PHA stimulation caused an increase in the IL-2 activity of the treated UCBL cultures. This effect was THF-gamma 2 dose dependent with an optimum in the range of 300-600 ng/ml and was not influenced by irradiation of the UCBL. These results indicate that THF-gamma 2, a synthetic octapeptide, modulates the immune state and response of human umbilical cord blood lymphocytes.