Bovine colostrum fraction as a serum substitute for the cultivation of mouse hybridomas

β-Lactoglobulin Influences Human Immunity and Promotes Cell Proliferation

β-Lactoglobulin (LG) is suspected to enhance or modulate human immune responses. Moreover, LG is also hypothesized to increase human cell proliferation. However, these potential functions of LG have not been directly or thoroughly addressed. In this study, we demonstrated that LG is a potent stimulator of cell proliferation using a hybridoma cell (a splenocyte fused with a myeloma cell) model. LG's ability to promote cell proliferation was lost when the protein is denatured. To further investigate the influence of LG's conformation on cell proliferation, we chemically modified LG by either carboxymethylation (CM) or acetylation and observed significantly reduced cell proliferation when the protein structure was altered. Furthermore, we proved that LG enhances cell proliferation via receptor-mediated membrane IgM receptor. These data indicated that nondenatured LG is the major component in milk that modulates cell proliferation. Collectively, our study showed that LG plays a key role in enhancing immune responses by promoting cell proliferation through IgM receptor.

Bovine colostrum promotes growth and migration of the human keratinocyte HaCaT cell line

Bovine colostrum represents a rich source of growth factors, which are known to play a central role in wound healing. The aim of our study was to investigate the possible mitogenic and motogenic effects induced by colostrum on human keratinocytes. Cell proliferation evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide test and 5-Bromo-2'-deoxyuridine incorporation revealed that colostrum exerts a growth promoting activity. Scratch assay and immunofluorescence of actin cytoskeleton showed its effectiveness also in inducing cell migration. Furthermore, colostrum treatment increases the levels of tyrosine phosphorylated proteins and the activated forms of the extracellular signal-regulated kinases 1 and 2 and such effects appear to be repressed by the tyrosine kinase inhibitor genistein. Our results indicate that the biological activities of colostrum are specifically mediated by the growth factor-induced activation of tyrosine kinase receptors and underline the relevance of the synergistic action exerted by the growth factors in stimulating keratinocyte proliferation and migration essential for tissue repair.

Biologically active factors in bovine milk and dairy byproducts: influence on cell culture

Substantial progress has been made in our knowledge of the biological properties of mammal milks. Many nutritional, biochemical, immunological, or other biological properties have been studied in mature or industrially processed bovine milk as well as in human milk and colostrum. This article is a critical review of selected publications covering (1) the use of bovine milk or dairy byproducts (processed acid and enzymatic whey fractions) as a serum substitute for cell cultures, (2) specific factors in bovine milk and industrially processed milk the affect cell proliferation, and (3) the known functional and biological roles of two whey proteins: beta-lactoglobulin and the PP3 component.

Inhibition of S-fimbria-mediated adhesion to human ileostomy glycoproteins by a protein isolated from bovine colostrum

The aim of this study was to isolate and purify the component in bovine colostrum which is responsible for the inhibition of S-fimbria-mediated adhesion of Escherichia coli. Whey from defatted colostrum was fractionated by ultrafiltration, and the < 100K, < 30K, and < 10K fractions and the colostral whey were tested for inhibition of in vitro adhesion of radiolabelled S-fimbria-bearing E. coli to human ileostomy glycoproteins, which provide a model for human intestinal mucus. The inhibiting compound was purified from a dialyzed < 30K fraction with an anion exchange column which was eluted with a NaCl gradient (0 to 1.0 M). The compound was found to be a heat-resistant but pepsin-sensitive protein with an Mr of approximately 18,000 and an isoelectric point of approximately 5.75. The protein appears to block receptor sites for S-fimbriae on ileostomy glycoproteins, with steric hindrance being the most likely mechanism. Analysis of the amino acid sequence of the amino terminus of the 18K protein showed similarity with the sequence of beta-lactoglobulin.

Milk-derived growth factors as serum supplements for the growth of fibroblast and epithelial cells

We have investigated the response of several epithelial and fibroblastic cells to a mitogenic extract of bovine milk. Cation exchange chromatography was used to produce a mitogen-rich fraction from an industrial whey source that, although comprising only 0.5% of total whey protein, contained the bulk of the growth factor activity. This fraction was a source of potent growth promoting activity for all mesodermal-derived cells tested, including human skin and embryonic lung fibroblasts, Balb/c 3T3 fibroblasts, and rat L6 myoblasts. Maximal growth of all these cell types exceeded that observed in 10% fetal bovine serum. Feline kidney and baby hamster fibroblasts and Chinese hamster ovary cells were less responsive, achieving a maximal growth response of 50-75% that observed in 10% fetal bovine serum. Maximal growth achieved in whey-extract-supplemented cultures of Balb/c 3T3 and human skin fibroblasts, and L6 myoblast cultures exceeded that seen in response to recombinant acidic or basic fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or epidermal growth factor. Importantly, addition of low concentrations of fetal bovine serum to the whey-derived mitogenic fraction produced an additive response. However, concentrated milk-derived factors were found to be inhibitory to the growth of all epithelial lines tested, including rat intestinal epithelial cells, canine kidney epithelial cells, and mink lung cells. It is concluded that industrial whey extracted in this form constitutes an important source of potent growth-promoting agents for the supplementation of mesodermal-derived cell cultures.

Bovine colostrum ultrafiltrate supplemented with adult bovine serum and transferrin: an effective FBS substitute for cultivation of Vero and CHO-K1 cells

A mixture containing an ultrafiltrate fraction (UF) of bovine colostrum (6.7%), adult bovine serum (BS) (1%), and human holo-transferrin (hTF) (5 mg/liter) was developed for cultivation of Chinese hamster ovary cells (CHO-K1) and African green monkey kidney cells (Vero). The growth-supporting activity of the mixture (UF/BS/hTF) was comparable to that of 1 to 10% fetal bovine serum (FBS) and considerably better than 1 to 2% BS. Cells could be directly seeded from FBS-supplemented medium to UF/BS/hTF-supplemented medium without any weaning period, even at initial plating density of 1700 cells/ml. Vero and CHO-K1 cells were cultivated in UF/BS/hTF-supplemented media for up to 43 days without any apparent reduction in growth. The UF/BS/hTF mixture could also be used as a freezing medium. Cells were passaged twice in the mixture, frozen, and stored at liquid N2 for 11 wk. After thawing, the viability of Vero and CHO-K1 cells was reduced 13 and 7%, respectively, and both cell lines started to grow well. Additional hTF could be replaced with bovine holo-transferrin, although a high concentration (150 mg/liter) should be used for CHO-K1 cells. The results suggest that the UF/BS/hTF mixture provides a new economical alternative to FBS in cultivation of Vero and CHO-K1 cells in the presence of reduced protein amounts.

Bovine colostrum ultrafiltrate: an effective supplement for the culture of mouse-mouse hybridoma cells

An ultrafiltrate fraction (UF) of bovine colostrum has been successfully used as a cell culture supplement for growth and monoclonal IgG antibody production of cultured mouse-mouse hybridomas derived from spleen cells. In this study we compared the ability of UF to support growth and antibody production of IgA hybridomas derived from Peyer's patch cells with that of an IgG hybridoma cell line. One IgG (LPC2) and two IgA hybridoma cell lines (RB3 and P2E7) were used as models. The optimal UF concentration for Ig production and cell growth for both the IgA hybridoma RB3 and the IgG hybridomas was 5-10%. Initial plating density was found to be a critical factor for IgA hybridoma cell growth: the IgA hybridomas required a seeding density of at least 70,000 cells/ml to grow compared to 15,000 IgG hybridoma cells/ml (Pakkanen et al., 1992). The addition of small amounts (up to 2%) of FBS in 10% UF supplemented medium did not enhance IgA production or cell growth. RB3 and LPC2 cells seeded at equal density and grown in 10% UF for 8 days attained maximum cell densities at 3-4 days that were 58% (RB3) or 34% (LPC2) lower than those in 10% FBS, but the total amounts of monoclonal antibody produced were 73% and 83%, respectively, of that in 10% FBS. Thus, Ig production per cell was 22-27% higher in 10% UF than in 10% FBS. Hybridoma cells could be cultured for at least 5 weeks without any reduction in growth rates, if medium was partially but not completely replaced twice a week. This suggests that hybridoma cells maintained in UF supplemented medium secrete growth promoting factors. Cells maintained in UF for up to 5 weeks sustained similar monoclonal antibody production rates as in short term culture. These results show that UF can be used as an economical and effective hybridoma culture supplement for the production of both IgG and IgA antibodies.