Cell-mediated immune function in lambs chronically treated with dexamethasone.

Abstract

Crossbred ewe and wether lambs were individually stanchioned in environmentally controlled rooms at 20 degrees C. On d 0, lambs were treated with .04 mg of dexamethasone (DEX; n = 10)/kg of BW or given an equal volume of saline vehicle (SAL; n = 10). Treatment was repeated every 48 h for 14 d. Samples of blood were obtained by puncture of the jugular vein on d 0 (before treatment), 2, 4, 7, 10, and 14. Total and differential leukocyte numbers, lymphocyte blastogenic responses to mitogens, and in vitro production of interleukin-2 (IL-2) were determined. No treatment x day interaction was noted for any of the experimental end points (P greater than .10); therefore, within-day comparisons between DEX- and SAL-treated lambs were not made. However, over all 14 d, DEX-treated lambs had increased (P less than .05) numbers of lymphocytes (6.5 +/- .4 vs 5.1 +/- .4 x 10(3) cells/microliters for SAL) and monocytes (.8 +/- .1 vs .6 +/- .1 x 10(3) cells/microliters for SAL), and these increases contributed to an increase (P less than .01) in total leukocytes (11.2 +/- .5 vs 9.1 +/- .5 x 10(3) cells/microliters for SAL). Lymphocyte blastogenic responses to mitogens were not affected by DEX treatment. Production of IL-2 was reduced (P less than .05) for DEX- (.90 +/- .12 units/ml) compared with SAL-treated lambs (1.27 +/- .13 units/ml). The data suggest that continued treatment of lambs with DEX may result in a modest reduction in production of IL-2, but mitogen-stimulated blastogenic responses of lymphocytes are not reduced by DEX treatment.

Effects of beta-adrenergic receptor agonist and low environmental temperature on the immune system of growing lambs

“…Individual animal variations in leukocyte profile and lymphocyte functions might also account for variable results (Blecha et al 1984;Minton and Blecha 1990;Minton and Blecha 1991). In general, our results are close to those of previous studies, e.g., Minton and Blecha (1991) reported that total leukocytes, lymphocytes and neutrophils for lambs under conventional conditions were 9100, 5100 and 2800 cell µL -1 , respectively. The concentration of monocytes was decreased by the beta-agonist (Fig.…”

Uso da ciclofosfamida em modelo de imunodepressão experimental em ovinos

“…Por outro lado, modelos considerados bons para uma determinada espé-cie nem sempre se aplicam a outra. Em experimento anterior, Garcia et al (1999) não conseguiram provocar imunodepressão em ovinos com a dexametasona, resultado semelhante ao encontrado por Minton & Blecha (1991), apesar de diversos autores terem obtido sucesso em provocar a imunodepressão com a mesma droga em outras espécies (Roth & Kaerbele 1985, Pruett et al 1987, Wira et al 1990, Isobe & Lillehoj 1993, Doherty et al 1995, Bakker et al 1997). Assim, a principal motivação deste experimento foi a de avaliar o efeito de outra droga, a ciclofosfamida, em modelo de imunodepressão em ovinos.…”

“…Tal efeito foi bem documentado em várias espécies, como bovinos (Roth & Kaerbele 1985, Pruett et al 1987, Doherty et al 1995, ratos (Wira et al 1990, Bakker et al 1997) e até galinhas (Isobe & Lillehoj 1993). Todavia, Saulnier et al (1991) falharam ao tentar demonstrar o efeito imunodepressor da dexametasona em suínos e Minton & Blecha (1991) e Garcia et al (1999) também não conseguiram encontrar tal efeito em ovinos.…”

Cortisol and Immune Measures in Boars Exposed to Three-day Administration of Exogenous Adrenocorticotropic Hormone

“…In other studies, pigs exposed to acute stress such as shipping did not show changes in total leukocyte count (McGlone et al, 1993;Hicks et al, 1998). Increased leukocyte counts were found during the administration of dexamethasone, a synthetic glucocorticoid, every 48 h for 2 weeks in lambs (Minton and Blecha, 1991).…”

“…Numerous studies have demonstrated negative e¡ects of various stressors on the lymphocyte proliferative function mediated by cortisol in pigs (Keller et al, 1981;Brown-Borg et al, 1993;McGlone et al, 1993;Wallgren et al, 1994;Ekkel et al, 1995;Puppe et al, 1997;Deguchi and Akuzawa, 1998). Cortisol primarily in£uenced T-lymphocyte activation through suppression of interleukin-2 production (Minton and Blecha, 1991;Wallgren et al, 1994), which most likely resulted from glucocorticoid interference with transcription of the genes for cytokines (Northrop et , 1992). It has been shown that lymphocyte count decreases simultaneously with neutrophil increase in stressful situations such as shipping (McGlone et al, 1993;Hicks et al, 1998).…”