Abstract: 21

CHARACTERIZATION OF IMMUNE CELL POPULATIONS IN THE BOVINE CORPUS LUTEUM.

CL O'Connor¹ , DH Townson^{1 *}
Dept of An.& Nutr.Sci.,Univ of New Hampshire, Durham, NH, USA ¹

Immune cells are thought to have a role in luteal function in the cow, yet there is little information available about these cells within the corpus luteum (CL). Here we have characterized in cow CL populations of immune cells throughout the estrous cycle. Ovulation (D0) was synchronized in cows with GnRH/prostaglandin F₂. Blood was taken prior to tissue collection, and CL were removed on D6 (n=4 cows), D12 (n=3), and D18 (n=4) postovulation. Frozen sections of CL were incubated with antibodies against monocytes (DH59B), macrophages (EBM11), and CD4+ & CD8+ T-lymphocytes (IL-All & MCA837). Cells stained positively were quantified in multiple low power fields (lpf) of multiple sections on coded slides. Plasma progesterone confirmed functional CL in D6 and D12 cows, and the onset of luteolysis in 2 of 4 cows at D18. Monocytes were the most abundant immune cell detected: CL at D6 contained the fewest monocytes (40±4 cells/lpf; p<.01) compared to CL of cows at D12 and D18 (range 54–95 cells/lpf). Numbers of macrophages were similar in CL of D6 and D12 cows (18–29 cells/lpf), but increased significantly by D18 (36±4 cells/lpf; p<.05). CD4+ cells were relatively sparse: CL at D6 contained the fewest cells (10±2 cells/lpf; p<.01) compared to CL at D12 and D18 (23–31 cells/lpf). Similarly, CL of D6 cows contained fewer CD8+ cells (19±2 cells/lpf; p<.01) than CL of D12 and D18 cows (28–52 cells/lpf). These results show that immune cells increase in CL of cows by D12-D18 postovulation, which might explain why the CL is most responsive to luteolytic stimuli during this period.[USDA 97–35208–4705 & 98–35208–6654]

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.