Vitamin A Supplementation in Early Life Enhances the Intestinal Immune Response of Rats with Gestational Vitamin A Deficiency by Increasing the Number of Immune Cells

Vitamin A is a critical micronutrient for regulating immunity in many organisms. Our previous study demonstrated that gestational or early-life vitamin A deficiency decreases the number of immune cells in offspring. The present study aims to test whether vitamin A supplementation can restore lymphocyte pools in vitamin A-deficient rats and thereby improve the function of their intestinal mucosa; furthermore, the study aimed to identify the best time frame for vitamin A supplementation. Vitamin A-deficient pregnant rats or their offspring were administered a low-dose of vitamin A daily for 7 days starting on gestational day 14 or postnatal day 1, day 14 or day 28. Serum retinol concentrations increased significantly in all four groups that received vitamin A supplementation, as determined by high-performance liquid chromatography. The intestinal levels of secretory immunoglobulin A and polymeric immunoglobulin receptor increased significantly with lipopolysaccharide challenge in the rats that received vitamin A supplementation starting on postnatal day 1. The rats in this group had higher numbers of CD8(+) intestinal intraepithelial lymphocytes, CD11(C) (+) dendritic cells in the Peyer's patches and CD4(+)CD25(+) T cells in the spleen compared with the vitamin A-deficient rats; flow cytometric analysis also demonstrated that vitamin A supplementation decreased the number of B cells in the mesenteric lymph nodes. Additionally, vitamin A supplementation during late gestation increased the numbers of CD8(+) intestinal intraepithelial lymphocytes and decreased the numbers of B lymphocytes in the mesenteric lymph nodes. However, no significant differences in lymphocyte levels were found between the rats in the other two vitamin A supplement groups and the vitamin A-deficient group. In conclusion, the best recovery of a subset of lymphocytes in the offspring of gestational vitamin A-deficient rats and the greatest improvement in the intestinal mucosal immune response are achieved when vitamin A supplementation occurs during the early postnatal period.