<prompt> In Vitamin A deficiency, respiratory tract infection due to:Keratinization of upper epithelial cellsLack of antibody productionDysfunction of epithelial layerDefective chemotaxis  <response>: Vitamin A: - Role 1 Vision 2 Reproduction growth 3 Maintenance of epithelial cell 4 Stabilization of cellular and intra Cellular membrane 5 Synthesis of glycoprotein 6 Antioxidant 7 Skin Bone Metabolism 