Prostaglandin F2α Induces Pro-Inflammatory T Lymphocyte Phenotypes in the Bovine Corpus Luteum.

Abstract

Lymphocytes are present in the fully functional corpus luteum (CL) and have been shown to proliferate during luteal regression due to migration into, as well as proliferation within, the tissue. Previous work in our laboratory has demonstrated that functional interactions exist between peripheral T lymphocytes (PTC) and luteal cells in culture. Functionally distinct classes of lymphocytes express distinctive cell surface proteins. Thus, we hypothesize that the function, based on cell surface proteins, of resident T lymphocytes (RTC) in the CL are dependent upon luteal status, either functional or regressing. We previously demonstrated that gamma-delta positive (γδ+) lymphocytes responded to luteal cell stimulation in vitro and were capable of producing both pro-and anti-inflammatory cytokines. Based on those results, the objectives of the present study were to: 1) isolate and characterize functional classes of RTC based on cell surface proteins; 2) compare RTC phenotypes from midcycle or 8 hour post PGF2α CL to PTC phenotypes, and 3) determine if lymphocyte populations isolated from CL or peripheral blood change as a result of prostaglandin (PG) F2α injection. Peripheral and resident T lymphocytes were isolated from whole blood and from dissociated luteal cell suspensions immunomagnetically by positive selection for cell surface proteins (CD2 and γδ). This procedure has been validated in our laboratory and yielded a population of cells that were ≥95% pure T cells. Lymphocytes were labeled with specific antibodies and analyzed to evaluate functional phenotypes. These analyses revealed the presence of pro-inflammatory (CD4+,γδ+ WC1+) and anti-inflammatory (γδ+ CD8+) lymphocytes in both RTC and PTC. Analysis of RTC from midcycle CL (n=4) and 8 hr post PGF2α CL (n=5) revealed a notable decrease in γδ- CD8+ lymphocytes after a luteolytic injection of PGF2α. In contrast, after a luteolytic injection of PGF2α RTC displayed an increase in γδ- WC1+ lymphocytes (p<0.01) and a numerical increase of γδ+ WC1+ lymphocytes. Additionally, there was a small increase in CD4+ lymphocytes after a luteolytic injection of PGF2α. In peripheral blood, a greater proportion of γδ+ CD8+ lymphocytes was observed in midcycle (n=4) compared to after PGF2α injection (n=5). Moreover, an increase in γδ+ WC1+ lymphocytes was observed in PTC after a luteolytic injection of PGF2α. Overall, comparison of RTC to PTC demonstrated a smaller percentage of positively labeled γδ+ (p<0.05), CD4+ (p<0.05), and WC1+ (p<0.05) lymphocytes isolated from the CL than from peripheral blood. However, the percentage of positively labeled CD8+ lymphocytes was greater in RTC than in PTC (p<0.0001). Based on these data, it is concluded that when the CL is fully functional, such as at midcycle, the RTC are predominately anti-inflammatory, however upon the induction of luteolysis with PGF2α, the proportion of pro-inflammatory lymphocytes is increased. These are the first data collected in any species to demonstrate a shift in functional phenotypes of T lymphocyte subsets isolated from the corpus luteum. Further, differences in T lymphocyte subsets within the CL compared to those in the peripheral circulation implies tissue-specific regulation of lymphocyte trafficking and/or proliferation. This project was supported by National Research Initiative Competitive Grant no. 2004-35203-14789 from the USDA Cooperative State Research, Education, and Extension Service.