Antibacterial and immunostimulating casein-derived substances from milk: casecidin, isracidin peptides.

Apart from immunoglobulin A and G antibodies and plasma cells, milk also contains antibiotic/host protective peptides that are of value not only for maintenance of its nutritional integrity but also for protection of the newborn and, possibly, protection of the lactating mother. Among the first such peptides identified with casecidin; following chymosin digestion of casein at pH 6 or 7, casecidin inhibited in vitro staphylococci, sarcina, Bacillus subtilis, Diplococcus pneumoniae and Streptococcus pyogenes. Inhibition occurred at high concentrations, in vitro, compared with commercial antibiotics, and thus interest in casecidin languished.