Cellular sources of thymic hormone (thymosin) in human thymus.

Antiserum against partially purified calf thymosin (5) was used for the localisation of this complex material in human thymus for comparison with calf thymi. Antithymosine IgG produced with human thymosin 5 by comparative immunoelectrophoresis one line identical with one of the lines of calf thymosin 5. Immunofluorescent evidence suggests the presence of the material in question, which also contains a biologically active principle, mainly in the epithelial cells of the thymus cortex. The contents of the traced material, however, fluctuates substantially between individual thymic lobules.