Studies on the Inflammatory Response During Involution of the Ovine Mammary Gland

Abstract

SUMMARYCessation of lactation, initiated by the removal of lambs from their mothers, induced an inflammatory response with elevated numbers of neutrophil leucocytes in mammary secretions being detected within 16 h. Leucocyte numbers were still elevated 7 d later. Infusion of whole milk into non-lactating glands caused no change in leucocyte numbers after 24 h. Involution secretions, however, had the capacity to induce an inflammatory response when infused into non-lactating glands. Daily infusion of endotoxin (100 ng) into non-lactating glands resulted in a marked attenuation of the inflammatory response. Such desensitization did not accompany reinfusion of involution secretion. Responses to involution secretion were enhanced in glands desensitized to endotoxin. The failure of desensitization to develop in glands receiving repeated infusions of involution secretion and the lack of cross-desensitization between involution secretion and endotoxin indicate that a novel mediator of inflammation may be produced during mammary involution in sheep.

Involution of the mouse mammary gland is associated with an immune cascade and an acute-phase response, involving LBP, CD14 and STAT3

“…Although the early presence of neutrophils and the late presence of macrophages have been reported in the involution secretions of many species, including pigs, guinea pigs, sheep and cows [ 42 - 45 ], the same has not been reported for rats, humans or mice [ 30 ]. Our gene expression data strongly support a role for these cells during mouse mammary gland involution because the neutrophil-specific chemokine GRO1/CXCL1 was specifically upregulated fivefold on the first day of involution, and the neutrophilic-granulocyte marker LRG [ 46 ] was upregulated most strongly on day 2 after forced weaning (Fig.…”

Growth Hormone and Milking Frequency Act Differently on Goat Mammary Gland in Late Lactation

“…The opening of tight junctions in the case of once-daily milking could result from an inflammatory response due to the accumulation of milk in the cistern. It was observed that milk from distended udders of ewes exhibited more inflammatory activity (Colditz, 1988). Growth hormone has been reported to enhance neutrophil function and thus promote inflammation (Burvenich et al, 1999).…”

Survey of intramammary infections in ewes on the New England Tableland of New South Wales

“…The methods used in this survey may provide a slight underestimate of the prevalence of infection because the threshold value for cell count on doubtful specimens was deliberately set at a high value (750,000 cells/ml). This value was selected on the basis of recent evidence from this laboratory indicating that lactating ewes which are separated from their lambs for 24 h often have quite high neutrophil counts in milk without evidence of infection (Colditz 1988).…”