LOCALIZATION OF GROWTH-HORMONE MESSENGER-RIBONUCLEIC-ACID IN THE HUMAN IMMUNE-SYSTEM - A CLINICAL RESEARCH-CENTER STUDY

GH is an immunomodulatory factor that can be synthesized and secreted by mononuclear leukocytes. To determine if GH can be produced by the h uman immune system, we assessed the presence of GH messenger RNA (mRNA ) in both normal and abnormal human lymphoid tissues by RT-PCR and non isotopic in situ mRNA hybridization. The predicted PCR product of 161b p from human thymus, spleen, tonsil, lymph node, thymoma, and T and B cell lymphomas was similar to the product amplified From the human pit uitary. Restriction enzyme digestion confirmed that complementary DNA generated using GH primers originated from GH mRNA. Furthermore, we pe rformed in situ hybridization to localize the GH mRNA-positive cells. A hybridization signal for CH mRNA was found in all tissues examined. The distribution patterns of GH in normal lymphoid tissues suggested t hat GH can be produced by lymphocytes, as well as endothelial cells an d other cell types. Also, GH mRNA-positive cells were distributed diff usely throughout T and B cell lymphomas and a thymoma. Our results dem onstrate GH gene expression in normal and neoplastic human lymphoid ti ssues including nonlymphoid cells. This finding supports the hypothesi s that the human immune system is an extrapituitary site of GH gene ex pression that may serve as an autocrine/paracrine factor in immunomodu lation.