EXPRESSION OF GROWTH-HORMONE RECEPTORS IN MURINE LYMPHOID-CELLS ANALYZED BY FLOW CYTOFLUOROMETRY

We have analyzed the expression of GH receptors (GHR) in murine lympho id organs using flow cytofluorometry with biotinylated bovine GH and s pecific fluorescein isothiocyanate-labeled monoclonal antibodies defin ing distinct lymphoid cell populations. GHR were widely expressed in a ll murine hematopoietic tissues and in fetuses, newborns, and 3- and 7 -week-old animals. In the bone marrow, all hematopoietic lineages expr essed variable levels of GH receptors, whereas in the thymus, this exp ression was mainly seen in CD4(-) CD8(-), CD4(+) CD8(+), and CD8(+) su bpopulations. At the periphery, 50% of splenocytes and peripheral bloo d lymphocytes and 20% of lymph node cells were GHR positive, with a wi der receptor expression on B cells and macrophages (similar to 50%) th an on T cells (similar to 20%), where the labeling was seen on both CD 4(+) and CD8(+) cell subsets. interestingly, the proportion of GHR-bea ring CD4(+) and CD8(+) splenocytes significantly increased after T cel l activation with Concanavalin A or anti-CD3. Finally, we demonstrated that all peripheral T cells expressing GHR also expressed PRL recepto rs. Our study provides a molecular basis to study the factors controll ing GHR expression and to better understand the influence of GH in the regulation of immune function.