Abstract
The effect of thymosin fraction 5 (of calf origin) on the response to PHA and Con A by lymphocytes from different organs of human fetus was studied. The cells were isolated from the liver, thymus, spleen and bone marrow of 15 fetuses at 9-23 wks of gestation, and preincubated with different concentrations of thymosin. The increasing effect of thymosin on the mitogen responses was most obvious with thymus and spleen cells at 15-23 wks of gestation. Responses by fetal liver cells were only occasionally increased by preincubation with thymosin, and responses of fetal bone marrow were affected not at all. These results are different from the effects of thymosin on fetal lamb cells; our earlier work has indicated that, in the fetal lamb, the effect of thymosin is most pronounced on the early fetal liver cells. These findings led us to conclude that mitogen responses of fetal lamb lymphocytes or lymphocyte precursors can be induced by thymosin in the cells which have not yet reached those responses spontaneously. However, if the cells have already reached the stage where a response occurs naturally, it cannot be increased any more by preincubation with thymosin (Leino et al., 1977). The present findings on human fetal lymphocytes are compatible with these conclusions if the findings on fetal liver cells are excluded. Whether differences between human and sheep cells are attributable to restrictions in the species specificity of thymosin remains at the present unknown.
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Leino, A., Hirvonen, T., Soppi, E. et al. Effect of thymosin on PHA and Con A responses by human fetal lymphocytes. Pediatr Res 13, 83 (1979). https://doi.org/10.1203/00006450-197901000-00084
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DOI: https://doi.org/10.1203/00006450-197901000-00084