Define the Role of Vitamin A in immune response?

Vitamins A is essential to normal immune function and- regulation. As discussed above, during vitamin A deficiency the goblet cell numbers are reduced in epithelial tissues and as a consequence, mucous secretions (with their antimicrobial components) diminish. Cells lining protective tissue surfaces fail to regenerate and differentiate; hence they flatten and accumulate keratin.  Both factors - the decline in mucous secretions and loss of cellular integrity- reduce the body's ability to resist invasion from potentially pathogenic organisms. Pathogens can also compromise the immune system by directly interfering with the production of some types of protective secretions and cells.