Peripheral and intrauterine neutrophil function in the cow: The influence of endogenous and exogenous sex steroid hormones

It has been accepted for many years that the susceptibility of the genital tract to infection is reduced during the follicular phase compared with the luteal phase of the estrous cycle. Since the role of intrauterine neutroph ils is paramount in the elimination of bacteria, it can be hypothesized tha t these differences in resistance to infection could be mediated by differe nces in uterine-derived neutrophil function. In order to test this hypothes is two groups of cows were used in this study. Group 1 cows (n=5) were stud ied at estrus, diestrus, after ovariectomy, after exogenous estradiol and a fter progesterone treatment, at which time they underwent intrauterine infu sion with 1% oyster glycogen (OG) and a bacterial-free filtrate (BFF) of Ac tinomyces pyogenes (BFF), the latter having been recovered from a clinical case of endometritis; neutrophils were harvested by flushing from the lumen 15 to 18 h later. A peripheral blood sample was collected at the time of f lushing for the assay of estradiol and progesterone for a WBC and different ial count and for the harvesting of neutrophils using a Percoll single-stag e discontinuous gradient. After the recovery of the cells they were re-susp ended in HBSS. Group 2 (n=4) were infused with BFF during during all reprod uctive states as Group 1, but with OG only after ovariectomy and after trea tment with progesterone and estradiol. Neutrophil chemotaxis was assessed b y measuring their migration using a modified Boyden chamber and Zymogen-act ivated serum as a chemoattractant. Phagocytic activity was measured by dete rmining the number of Candida albicans ingested by each neutrophil after in cubation. The percentage of kill was determined using a radiometric assay i n which C. albicans was labeled with L-(5-H-3) Proline. Peripheral WBC concentration was not influenced by the reproductive state o f the cow; however, the mean neutrophil concentration was significantly dif ferent between the reproductive states (P<0.001) and between individual cow s (P<0.001). In Group 1, there was little difference in the function of the peripheral and uterine neutrophils, and while there were differences in al l 3 aspects of neutrophil function from both sources between reproductive s tates and individual cows, of which some were statistically significant, th ere was no consistent pattern. In Group 2, neutrophils recovered after the infusion of BFF had poorer function compared with those recovered after the infusion of OG. There was no consistent influence of the reproductive stat e or individual animal. The hypothesis that the influence of the reproducti ve state of the cow on the resistance of the uterus to infection is mediate d by the inherent differences in either peripheral or intrauterine neutroph il function was not supported by this study. (C) 2000 by Elsevier Science I nc.