Changes in Localization of T Cell Subsets in the Ovarian Follicles during Follicular Growth and Ovulation in Hens

Abstract

Changes in the localization of helper and killer T cells (CD4⁺ and CD8⁺ T cells, respectively) in hen ovarian follicles with follicular growth and ovulation were examined in this experiment. White follicles (WF), the largest and the third largest preovulatory follicles (F₁ and F₃, respectively) and the largest postovulatory follicle (POF) were collected from birds after 5hrs of oviposition. Cryostat sections were prepared and immunostained for T cells using antibodies to CD4 (antigen of helper T cells) and CD8 (antigen of cytotoxic T cells). Populations of positive cells were observed under a light microscope and counted using a computer assisted image analyzer. The CD4⁺ and CD8⁺ T cells were localized in the theca interna and externa of all examined follicles. The frequencies of CD4⁺ and CD8⁺ T cells in the theca interna were similar among each type of follicles. The frequency of CD4⁺ T cells in the theca externa was significantly decreased in F₃ and F₁ compared with WF, with a further decrease in POF (P<0.05), and that of CD8⁺ T cells was lower in F₃, F₁ and POF than WF (P<0.01). The ratio of CD4⁺/CD8⁺ T cells in the theca interna was similar among each type of follicles but significantly lower in the theca externa of POF than WF, F₃ and F₁ (P<0.05). These results suggest that the T cell subsets, responsible for cell mediated immunity, are reserved in the theca layer of ovarian follicles, whereas their population decreases with follicular growth in theca externa.