Retinol and retinol-binding protein: Gut integrity and circulating immunoglobulins

Vitamin A (retinol) is required to maintain immunity and epithelial turnove r and is a key micronutrient needed for combating infection. Vitamin A acti ons on the immune system are diverse and cannot be accounted far by a singl e effect or mechanism. The actions of retinol in maintaining gut integrity in humans and immunoglobulin levels in mice was investigated. For 30 childr en, performance on the lactulose/mannitol test, a test commonly used to ass ess intestinal barrier function, was inversely correlated (P = .012) with s erum retinol concentrations. Thus, children with lower serum retinol, and p resumably poorer vitamin A nutritional status, are more likely to have impa ired intestinal integrity. Knockout mice that have impairments in plasma re tinol transport have circulating immunoglobulin levels that are half those observed in matched wild type mice. No differences were observed in B and T cell populations present in spleen, thymus, and bone marrow.