AdvisorLarson, Douglas F.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractIt has been suggested by immune system studies that pituitary prolactin (PRL) may have an immunomodulatory role and that lymphocytes themselves may produce prolactin-like proteins (Ly-PLP). The studies in this dissertation focused on Ly-PLP production and PRL/Ly-PLP actions in an enriched population of rat splenic T helper (TH) CD4 and cytotoxic CD8 cells. Studies were planned on a dual hypothesis: first, that T-cells produce Ly-PLP which may act in an autocrine manner and second, that Ly-PLP may be necessary for interleukin 2 (IL-2) production. To study the possible mechanisms by which PRL and Ly-PLP regulate lymphocyte proliferation, a PRL-free medium was used and a polyclonal antibody to rat PRL (A-PRL) was used to inactivate the residual PRL and the expressed Ly-PLP in the cell culture system. This antibody inhibited T-cell proliferation in both a time and a concentration-dependent manner. Based on four lines of evidence, the in vitro inhibitory activity of A-PRL on cell proliferation appeared to be modulated in part by inhibition of IL-2 production. First, the A-PRL induced inhibition of T-cell proliferation was overcome by addition of recombinant human IL-2 (rhuIL-2). Second, A-PRL treatment of mitogen stimulated T-cells was shown by RT-PCR analysis to inhibit IL-2 mRNA expression. IL-2 receptor beta (IL-2rB) mRNA, which is constitutively expressed in T-cells, was not inhibited. Third, A-PRL inhibited IL-2 protein production in a concentration dependent manner. Fourth, the A-PRL induced inhibition of IL-2 production was overcome by preincubation of the A-PRL with purified rat pituitary PRL (rPRL). Dot Blot and RT-PCR analysis data in this dissertation were suggestive but were inconclusive in support of the hypothesis that rat lymphocytes and specifically T-cells constitutively express mRNA for PRL and/or Ly-PLP. Western blot studies of T-cell lysates suggested that rat T-cells express a Ly-PLP with the apparent molecular weight 46 kD, as well other variants. In summary the data presented in this dissertation indicate that rat T-cells expressed Ly-PLP and treatment with A-PRL to inactivate Ly-PLP inhibited cell proliferation, expression of IL-2 mRNA, and IL-2 protein expression by CD4 cells. The inhibition of IL-2 production was the likely mechanism by which A-PRL binding of Ly-PLP inhibited mitogen induced T-cell proliferation in rats. The inhibition of IL-2 production suggests that extracellular pituitary PRL or Ly-PLP through a hormone and/or an autocrine mechanism respectively may be necessary but not sufficient for the induction of IL-2 mRNA and IL-2 protein expression in activated rat T-cells.
Degree ProgramGraduate College
Pharmacology & Toxicology