Effect of bovine skim milk and whey on monocyte function

High frequency of Mycobacterium bovis DNA in colostra from tuberculous cattle detected by nested PCR

We evaluated by nested PCR reaction, different cow secretions from a herd with 48% of prevalence of bovine tuberculosis (BTB), seeking to determine niches where Mycobacterium bovis could be found. Postmortem examination of 18 (75%) tuberculin reacting cows allowed demonstrates BTB-compatible lesions in six, all of them PCR positives in milk and four in colostra samples. Our results showed that up to 62% of the colostra analysed contained M. bovis DNA, whereas only 18% of milk gave a positive reaction. Moreover, in bronchoalveolar lavages from cattle with compatible lesions in lungs or lymph nodes, where macrophages account up to 90% of cells, we did not find evidences of M. bovis. Altogether, these results suggest that differences in the anti-bacterial capacity of bovine macrophages, dependent upon microenvironment and organ-specific factors, exist. Alternatively, we hypothesize that hypoxic conditions that are encountered in mammary glands macrophages could induce M. bovis entrance into a 'dormancy-like' state, and that the high number of colostra samples were M. bovis was detected, could be an indicator of reactivation during 'peripartum'.

Immunomodulatory properties of milk

There is increasing commercial interest in the production of functional foodstuffs which have health-promoting properties. Over the last five to ten years, significant progress has been made in the identification and characterisation of bovine milk components that can affect the function of the immune system. This review outlines the major components of bovine milk that have been shown to modulate immune function, and discusses experimental approaches to the identification of various facets of the immune response that are known to be affected by milk-derived proteins.

Effects of purified bovine whey factors on cellular immune functions in ruminants

The immunomodulatory properties of bovine milk and whey have long been documented. The recent advance of whey protein fractionation technology has now allowed us to study the immunobiological properties of some highly purified components of whey, with a view to exploiting their possible industrial and biomedical applications. The effects of fractionated bovine whey proteins on cellular immune responses were therefore examined using a panel of in vitro assays. Both lactoferrin (LF) and lactoperoxidase (LP) were found to inhibit proliferation and interferon-gamma (IFN-gamma) production of ovine blood lymphocytes in response to mitogenic stimulation. However, their effects in a combined fraction or in whey protein concentrate (WPC) were either diminished or eliminated. LF and LP had no effect on lipopolysaccharide (LPS)-induced ovine blood lymphocyte proliferation, production of interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF alpha) by ovine bronchoalveolar lavage (BAL) macrophages, major histocompatibility complex (MHC) Class II antigen expression by ovine BAL macrophages and bovine natural killer (NK) cell activity. However, alpha-lactalbumin (alpha LA) exhibited an enhancing effect on IL-1 beta production. It is noteworthy that as bovine whey fractions become progressively more purified, their modulatory effects on the immune response also become more clear-cut. The effects of LF, LP and alpha LA may be eliminated by their combination in whey or by other minor components of whey. Further investigation of industrial applications for whey proteins of high purity is warranted.

Immunomodulatory activities of whey fractions in efferent prefemoral lymph of sheep

Studies on the immunomodulatory activities of ruminant milk and colostral whey fractions were undertaken. By comparing with boiled colostral whey in a preliminary experiment, a putative heat-labile immunostimulatory factor for antibody responses was found to be present in ovine colostral whey. Studies were then undertaken in sheep in which the efferent prefemoral lymphatic ducts were cannulated bilaterally, and immune responses in the node were measured following subcutaneous injection in the flank fold of whey protein preparations of various purities. A significant sustained decline of efferent lymphocyte output was observed following injection with autologous crude milk whey or colostral whey preparations, but no changes were observed in interferon-gamma levels in lymph plasma. Two bovine milk whey fractions (lactoperoxidase and lactoferrin) of high purity were compared in bilaterally cannulated sheep. A transient decline over the first 6 h was seen in the efferent lymphocyte output and lymph flow rate after injection of both fractions. A significant difference was seen between the two fractions in interferon-gamma levels in lymph at 6 h after injection. However, no significant changes in the proportion of the various efferent lymphocyte phenotypes were seen following either treatment. Whereas both fractions showed a significant inhibitory effect in a dose-dependent manner on the proliferative response of T lymphocytes, but not B lymphocytes, to mitogenic stimulation in vitro, no similar changes were seen following in vivo stimulation with these two fractions.