Studies on the modulation of leucocyte subpopulations and immunoglobulins following intramammary infusion of β1,3-glucan into the bovine udder during the dry period

Inflammatory and immunological reactions after intramammary infusion of beta 1,3-glucan were studied during the steady dry period and involution phase of the bovine udder. The effects of a single intramammary infusion of two different doses (100 and 200mg) of beta 1,3-glucan were evaluated during the steady dry period. In a second study the effects of beta 1,3-glucan at drying off were studied by using two treatment regimens; a single infusion at drying off, compared with Mo infusions of the compound, at drying off and again 2 weeks later. Total and differential leucocyte counts were measured in both blood and udder secretions. Additionally, the expression of receptors for CD14 and MHC class II on leucocytes, and the expression oFreceptors for CD4, CD8, WC1, IL2Rand B-cells on lymphocytes was measured in mammary secretions by flow cytometric analyses. The concentrations of immunoglobulins in udder secretions were measured by radial immunodiffusion. The results showed that a single intramammary infusion of beta 1,3-glucan during the steady dry period causes transient enhancement of some aspects of the inflammatory and immune responses. The increases in somatic cell counts, numbers of monocytes/macrophages, and in proportions of CD14 + and MHC class II + leucocytes in udder secretions were dose-dependent. Infusion of beta 1,3-glucan also slightly increased the proportion of CD4 + lymphocytes and the concentrations of IgG(1) and IgG(2) in dry secretions. Infusion of beta 1,3-glucan at drying off seemed to accelerate the involution process through an increase in somatic cells, particularly in the numbers of macrophages, in mammary secretions. The numbers of lymphocytes and polymorphonuclear leucocytes, the proportions of IL2R + lymphocytes, the proportions of CD14 + or MWC class II + leucocytes and the concentrations of IgG(1) and IgG(2) also increased in comparison with untreated controls. Moreover, a second infusion of beta 1,3-glucan tended to prolong this response, indicating that this might be an effective means of enhancing the mammary defence against udder infections closer to calving. In conclusion, the results indicate that intramammary infusion of beta 1,3-glucan could be used to enhance the defence mechanisms of the bovine udder against infections, especially during early involution.