PARENT SESSION
SLIDE SESSION 20: GENE EXPRESSION AND HORMONE / CYTOKINE REGULATION IN THE CORPUS LUTEUM
Chairs: Milo Wiltbank, Richard Stouffer, Matthew Cannon (Trainee)
Univ Ottawa-Monpetit 203
1:30 PM-3:30 PM

PRESENCE AND STEADY-STATE AMOUNTS OF mRNA ENCODING COSTIMULATORY MOLECULES CD80 AND CD86 IN BOVINE LUTEAL TISSUE DURING THE ESTROUS CYCLE AND PGF₂-INDUCED LUTEAL REGRESSION.

Cannon, Matthew¹, Pate, Joy¹, ¹

ABSTRACT- Evidence of immune system involvement in regulation of luteal function is accumulating. We have hypothesized that specific interactions dependent on major histocompatibility complex (MHC) molecules occur between luteal cells and T cells, and that these interactions may facilitate normal luteal function and regression. Bovine luteal cells express class I and II MHC molecules, and stimulate a greater degree of class II-dependent T cell proliferation in vivo following a luteolytic dose of PGF₂. We recently demonstrated the presence in bovine luteal tissue of mRNA encoding proteins necessary for intracellular processing of peptides presented to T cells via MHC molecules. This suggests that luteal cells can act as antigen presenting cells, interacting with T cells in a manner specific to and dependent on MHC molecules. In addition to MHC molecules, a costimulatory signal is necessary to facilitate interaction between antigen presenting cells and T cells. Our objectives were to confirm the presence and determine the steady state amounts of mRNA encoding two costimulatory molecules, CD80 and CD86, in bovine luteal tissue. Northern analysis using riboprobes specific for CD80 or CD86 was performed on RNA extracted from corpora lutea (CL, n=5/time point) removed early (day 5), during midcycle (day 10-12), or late (day 18) in the estrous cycle, and at 0, 0.5, 1, 4, 12 and 24 hours after injection of 25mg PGF₂. Amounts of CD80 and CD86 mRNA were greatest (p<0.05) at midcycle compared to day 5 and day 18 CL, and were similar between day 5 and day 18 CL. No changes were detected in amounts of CD80 or CD86 mRNA following PGF₂ administration. This indicates that luteal cells may express costimulatory molecules that would facilitate interaction of luteal cells with T cells. However, the patterns of mRNA expression were unexpected, and a clear role for costimulatory molecules in luteal tissue remains to be revealed.

KEY WORDS: corpus luteum, reproductive immunology, costimulatory molecules