Iron deficiency reduces serum and in vitro secretion of interleukin-4 in mice independent of altered spleen cell proliferation

Abstract

Iron deficiency, a worldwide public health problem in children and adult women, impairs innate and cell-mediated immunity including interferon-γ secretion. Its effects on interleukin (IL)-4 have not been well investigated. Interleukin-4, a cytokine primarily secreted by TH2 lymphocytes, regulates B-cell proliferation and the switching of immunoglobulin (Ig)M to IgE subtypes; the latter is involved in the defense against helminth infection. Considering the fact that interferon-γ is a potent inhibitor of IL-4, we hypothesize that iron deficiency would increase the secretion of IL-4 and IgE. We measured IL-4 in serum and supernatant of concanavalin A and anti-CD3 antibody-treated spleen cells from iron-deficient, control, pair-fed DBA and C57BL/6 mice (20-24/group) and iron-replete mice for 3, 7, and 14 days (8-13/group). Feeding the low-iron diet (5 ppm vs 50 ppm for the control diet) for 2 months significantly reduced the mean levels of hemoglobin, hematocrit, liver iron stores, thymus weight, and induced splenomegaly in both strains of mice (P < .001). Iron deficiency, and not pair-feeding, reduced plasma IL-4 levels (P < .05), although it did not significantly affect IgE levels. Iron deficiency, especially when associated with thymus atrophy, reduced in vitro IL-4 secretion by activated spleen cells, cell proliferation, and percentage of CD4⁺IL-4⁺ cells (P < .05). Impaired cell proliferation did not fully explain reduced in vitro IL-4 secretion because iron-deficient mice with a normal thymus weight had a normal (3)H-thymidine uptake but decreased supernatant IL-4. It was likely due to low percentage of CD4⁺IL-4⁺. Iron repletion improved IL-4 measurements. Data suggest that iron deficiency has generalized negative effects on T-cell function. Unaltered plasma IgE may be due to other cytokines (ie, IL-13) that also modulate its secretion.