Retinyl acetate (Vitamin A acetate) is a group of unsaturated nutritional hydrocarbons, that contains retinal, retinol, retinoic acid, and several provitamins A carotenoids, among which beta-carotene is the most important.

Vitamin A deficiency impairs innate immunity by impeding normal regeneration of mucosal barriers damaged by infection, and by diminishing the function of neutrophils, macrophages, and natural killer cells. Vitamin A is also required for adaptive immunity and plays a role in the development of T both-helper (Th) cells and B-cells. Vitamin A deficiency diminishes antibody-mediated responses directed by Th2 cells, although some aspects of Th1-mediated immunity are also diminished. [1]

Vitamin A acetate (VAA) (fed on an otherwise conventional diet) responds to 105 semiallogeneic cells (a suboptimal dose) in a host-versus-graft (HvG) reaction in mice, whereas mice on a conventional diet do not. [2] Vitamin A acetate can bring a solid and long-lasting state of tolerance induced by the intravenous injection into newborn CBA mice of lymphoid cells from (CBA X C57BL/10ScSn) F1 hybrids to an end, the effect of which is to increase the proportion of the moiety of the T-cell population that produces IL-2. [3] Vitamin A acetate-supplemented diet develops a positive skin reaction to purified protein derivative of mycobacteria in High-dose Mycobacterium bovis-infected mice, and their spleen cells show an increased IL-2 production in vitro. [4]