EFFECTS OF SUPPLEMENTAL CHROMIUM ON PRODUCTION OF CYTOKINES BY MITOGEN-STIMULATED BOVINE PERIPHERAL-BLOOD MONONUCLEAR-CELLS

This study determined whether supplementing the diets of dairy cows du ring the peripartum period with organic trivalent Cr influenced the ca pacity of their peripheral blood mononuclear cells to produce activati on cytokines in response to stimulation with mitogens in vitro. Nine c ows were fed 0.5 ppm of Cr/d per cow from 6 wk prepartum to 16 wk post partum; 10 other periparturient cows served as unsupplemented controls . Mononuclear leukocytes, enriched from peripheral blood during wk 0, 2, 4, and 6 of lactation, were cultured with or without the T-lymphocy te mitogen, concanavalin A. Culture supernatants, harvested at 24, 48, or 72 h, were assayed for interleukin-2, interferon-gamma, and tumor necrosis factor-alpha. The cytokines were barely detectable in the sup ernatants from the unstimulated cultures, but supernatants from mitoge n-stimulated cultures contained higher concentrations of each cytokine . For cows fed Cr, concentrations of all three cytokines in the cultur e supernatants of the mitogen-stimulated mononuclear cells decreased s ignificantly relative to values for unsupplemented cows, particularly around peak lactation for the 24- and 48-h cultures. Theses results ex tended our previous observations and supported the hypothesis that org anic Cr is immunomodulatory in high producing cows.