Effect of intramammary infusion of β-1,3-glucan or interleukin-2 on leukocyte subpopulations in mammary glands of sheep

Abstract

Abstract Objective To investigate effects of intramammary infusion of β-1,3-glucan or recombinant ovine interleukin-2 (rOvIL-2) on blood and mammary leukocyte subpopulations and their expression of various surface antigens in sheep. Animals 12 healthy multiparous, nonpregnant, non-lactating fine-wool Merino ewes. Procedure β-1,3-Glucan in pyrogen-free saline solution (PFSS; n = 6), rOvIL-2 in PFSS (3), or PFSS (3) was infused on days 0 and 7 in 1 udder half of each ewe. Jugular vein blood and mammary secretion samples were taken before infusion and on days 2, 7, and 21 after infusion. Total and differential leukocyte counts were obtained, and blood and mammary cells were labeled for flow cytometry. Results Slight swelling of the mammary glands was observed on day 2 after rOvIL-2 but not after β-1,3-glucan infusion. Both substances induced significant increase in mammary secretion leukocyte numbers, compared with controls. β-1,3-Glucan induced an influx of monocyte/macrophages, whereas neutrophils were the predominating cell population after rOvIL-2 infusion. β-1,3-Glucan induced selection for CD4+, B-cell+, WC1+, and L-selectin+ lymphocytes on day 14 after infusion. By comparison, rOvIL-2 induced selection for B-cell+ and L-selectin+ lymphocytes on days 14 and 21 and depletion of CD8+ and, to some degree, of IL-2R+ lymphocytes. β-1,3-Glucan induced an increase in the proportion of CD14+ leukocytes, indicating selective migration of monocyte/macrophages to the nonlactating udder. Conclusion β-1,3-Glucan and rOvIL-2 can modulate nonspecific immunity in the udder of sheep but may exert their effects by differing mechanisms. Clinical Relevance Stimulation of the nonspecific defense against udder infections may improve control of mastitis. (Am J Vet Res 1999;60:703–707)