DETECTION OF GROWTH HORMONE-PRODUCING CELLS IN HUMAN THYMUS BY IMMUNOHISTOCHEMISTRY AND NONRADIOACTIVE IN-SITU HYBRIDIZATION

It is well recognized that growth hormone (GH) may act as a growth and differentiation factor for the thymus gland. Recently, it has been re ported that Pit-1/GHE-1 transcription factor, which controls the expre ssion of both GH and prolactin, is expressed in stromal (not lymphoid) cells of human thymus. Here, we demonstrated by immunohistochemistry and in situ hybridization the presence of distinct GH-producing epithe lial cell subsets in human thymus. The cells positive for GH mRNA and GH-immunoreactive substance are both located in the same thymus compar tments, i.e., along the thymus capsule, in the subcapsular cortex, and within the septa. Local concentration of GH higher than systemic ones , in combination with other factors, may be important in regulating th e thymic microenvironment necessary for T-lymphocyte differentiation.