Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/1997
Publication Date: N/A
Interpretive Summary: The immune system helps defend the body against infectious diseases. In order to maximize the health of livestock, a better understanding of their immune system is required. Luteinizing hormone-releasing hormone (LHRH) is a chemical produced in the brain and is an important regulator of reproduction in mammals. The effects of LHRH are conveyed through LHRH receptors. Interestingly, LHRH and its receptors have been found in the immune systems of monkeys and rats. In these studies, we wanted to determine if LHRH and its receptors are produced in the immune system of the pig. Several body tissues in the pig were examined for evidence of LHRH and its receptor being produced. These tissues included two parts of the brain (hypothalamus and cortex), pituitary (a gland near the brain), liver, and three parts of the immune system (thymus, spleen, and white blood cells). We found evidence of LHRH production not only in the hypothalamus, as expected, but also in all of the parts of the immune system examined. LHRH receptor production was found in the pituitary gland, as expected, as well as in all parts of the immune system studied. We found no indication that LHRH or its receptors were produced in the cortex or liver, demonstrating that production of these compounds is restricted to certain parts of the body. In summary, this study provides evidence that LHRH and its receptor are produced in the immune system of the pig. And, though not yet demonstrated, this raises the possibility that LHRH is involved in the pig's defense against infectious diseases. A possible role for LHRH in mediating the immune response, and its impact on animal health, can now be examined in the pig.
Technical Abstract: Luteinizing hormone-releasing hormone (LHRH) is the primary regulator of pituitary LH release. In several mammals, however, LHRH has also been identified in extrahypothalamic sites including immune tissues. Accordingly, immunodulatory properties for LHRH have been suggested. In these studies, we wanted to determine if LHRH and its receptor are produced dby immune tissues in the pig. First, a cDNA was cloned and sequenced (dideoxy termination and incorporation of 35S-dATP) from the porcine hypothalamus that corresponded to preproLHRH. This cDNA showed 87.5% homology with the human LHRH gene. Internal primers were identified from this sequence for amplifying a 268 bp fragment by PCR. In addition to the hypothalamus, PCR products reflecting LHRH mRNA were successfully amplified in porcine spleen, thymus, and peripheral blood lymphocyte (PBL) cDNA. LHRH mRNA was not identified in liver, cerebral cortex, or pituitary tissue esamples. Primers were designed to amplify a 360 bp fragment of the LHRH-receptor gene. PCR products reflecting LHRH-receptor mRNA were identified in pig hypothalamus, pituitary, thymus, spleen and PBL cDNA samples. No such products were detected in cortex and liver samples. In summary, there is evidence that LHRH and its receptor are synthesized in the porcine immune tissues. This leads us to speculate that LHRH may have local immunomodulatory functions in the pig.