Vitamin A Levels and Immunity in Humans

In animal studies, vitaminA deficiencyinduces a shift from type 2 (humoral) to type 1 (cellular) cytokines; there are no similar data for humans. Control of human immunodeficiency virus (HIV) and Mycobacterium tuberculosis infections requires type 1 cytokine (cellular) immunity. These infections and vitaminA deficiencyare highly prevalent in Africa. We therefore examined the interactions among serum vitaminA levels, immune parameters, HIV infection status, Mycobacterium bovis BCG vaccinescarring (as an indicator of a type 1 cytokine profile), and clinical findings for 70 hospitalized children in Malawi, Africa. Directly conjugated monoclonal antibodies and flow cytometry were used to assess cell-specific cytokine production by peripheral blood monocytes and lymphocyte subpopulations. The statistical techniques employed included nonparametric statisticsand logistic regression analyses. Thirty percent of the participants had severe vitaminA deficiency( 20 g/dl). VitaminA levels were lower for HIV-positive than for HIV-negative children (median, 10 and 17 g/dl, respectively). VitaminA- deficientchildren (<20 g/dl) were more likely than non- vitaminA- deficientchildren to have higher proportions of natural killer (NK) cells (median, 8.3 and 5.2%, respectively) and lower ratios of interleukin10-producing monocytes to tumor necrosis factor alpha-producing monocytes after induction (median, 1.0 and 2.3, respectively). VitaminA- deficientchildren were also more likely than non- vitaminA- deficientchildren to exhibit respiratory symptoms (47% versus 12%) and visible BCG vaccinescars (83% versus 48%), which are indicative of a type 1 response to vaccination. VitaminA status did not vary with gender, age, incidence of malaria parasitemia, blood culture positivity, or rates of mortality (6% of vitaminA- deficientchildren died versus 20% of non- vitaminA- deficientchildren). Lower vitaminA levels were associated with a relative type 1 cytokine dominance and proportionately more NK cells, both of which may be somewhat beneficial to persons who are exposed to HIV, M. tuberculosis, or other type 1 pathogens.