Isolation and characterization of an immunomodulatory protein from bovine colostrum
A colostral protein that augments natural killer (NK) cell activity was isolated from bovine colostrum. This protein, designated matemal immunity enhancing factor (MIEF), increased NK cell-mediated cytotoxicity against human tumor targets when added to cultures of resting peripheral blood lymphocytes. The NK cell stimulatory activity of the MIEF was demonstrated at the concentrations as low as 0.1–0.01 μg/ml. Purified MIEF showed an apparent molecular weight of 22,000 in SDS-polyacrylamide gel electrophoresis. The unusual biochemical characteristics of the MIEF distinguish it from other cytokines. The MIEF was soluble at a cold temperature, and precipitated by raising the temperature. This thermal precipitability was reversible, and dependent on the concentration, pH, and ionic strength. Maximal precipitation was observed at neutral pH, and higher ionic strength.
Key wordsBovine colostrum Immunomodulation Natural killer cell Reversibly heat precipi-table protein
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