Rat Spleen Lymphocytes Contain an Immunoactive and Bioactive Luteinizing Hormone-Releasing Hormone

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Abstract
An interaction between the immune and endocrine systems has been long known. This associations is further strengthened by the finding that splenic lymphocytes have the capacity to produce molecules similar to if not the same as classical hormones, including several members of the opiate family, pRL, GH, and neuropeptide Y. Because of such findings and because of information from other laboratories suggesting that LHRH might have direct effects upon the immune system, we hypothesized that immune cells themselves might contain LHRH. Lymphocytes were purified from spleens of intact adult male Sprague-Dawley rats and the cells were lysed with sodium hydroxide. The concentration if immunoreactive LHRH was 403 .+-. 184 pg/20 .times. 106 lymphocytes. Increasing amounts of lymphocyte lysate displaced [125-I]LHRH form LHRH antibody in a manner parallel to that produced by synthetic hypothalamic LHR suggesting immunologic similarity between lymphocyte and hypothalamic LHRH. Lymphocyte LHRH-like immunoactivity coeluted from Nova-Pak C18 columns with synthetic hypothalamic LHRH. When lymphocyte lysates were applied to rat anterior pituitary cells in monolayer culture, significant stimulation of LHRH secretion was seen, from 2,144 .+-. 54 pg LH/ml.cntdot.4 h to 15,364 .+-. 587 pg LH/ml.cntdot.4 h (P < 0.001), a finding verified in five additional experiments. In other studies, this LH response evoked by lymphocyte lysates was found to be dose dependent and could be significantly inhibited by an LHRH-antagonist. Furthermore, when lymphcoyte lysate and identically treated synthetic LHRH were HPLC fractionated, there was coelution of lysate and hypothalamic LHRH bioactivity. The lysate itself contained no substantial LHR immunoreactivity. Thus, lymphocytes from spleens of adult male rats contain an immunoactive and bioactive LHRH, a finding further strengthening an association between the endocrine and immune systems.