|Ametaj, Burim - IOWA STATE UNIV., AMES|
|Beitz, Donald - IOWA STATE UNIV., AMES|
Submitted to: Autumn Immunology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 21, 1998
Publication Date: N/A
Technical Abstract: Periparturient dairy cows are supplemented frequently with vitamins A and D at concentrations greater than recommended by the National Research Council and because these vitamins are known modulators of immune function, this practice may influence the functional capacity of dairy cow's immune system. We evaluated in vitro the effects of 1,25(OH)2D3 alone and in combination with retinoic acid (9-cis or 9,13-di-cis-RA) on interferon-gamma (IFN-y) secretion by MNL from postparturient and nulliparous dairy cows. Animals were bled at calving and at 2, 4 and 16 d after parturition. The MNL-enriched populations were incubated (48 h at 39 C) with pokeweed mitogen (PWM, 10 ug/ml), 1,25(OH)2D3 (0.01-100 nM) alone or with combination of 9-cis or 9,13-di-cis-RA (0.01-100 nM). IFN-y secretion was quantified by ELISA. A group of 6 nonpregnant, age-matched, nulliparous cows served as controls. In all cows, 1,25(OH)2D3 or 9-cis-RA alone inhibited IFN-y secretion while 9,13-di-cis-RA alone had no effect. In postparturient cows, IFN-y secretion by MNL was low at parturition and at 2-4 d later, but by 16 d after calving, had increased by almost 3-fold. Combinations of 1,25(OH)2D3 and 9-cis- or 9,13-di-cis-RA acted synergistically in inhibiting IFN-y secretion by postparturient and control bovine MNL. Inhibition was greatest when 1,25(OH)2D3 at 1, 10 and 100 nM was present with 9-cis or 9,13-di-cis-RA at 0.01, 0.1 and 1 nM. High conc of 9-cis or 9,13-di-cis RA (10-100 nM) abrogated 1,25(OH2D3)-induced inhibition of IFN-y secretion. Overall, results suggest that biologically active metabolites of vit A and D influence IFN-y secretion by bovine MNL and suggest that excess supplementation with these vitamins may affect the bovine immune system.