Antibacterial activity of bovine blood neutrophils and their cationic proteins

Six cationic protein bands were identified in extracts of both normal bovine blood neutrophils and their granules subjected to polyacrylamide disc gel electrophoresis. Band 1, the most cationic protein, was as positively charged as crystalline egg white lysozyme, and band 2 was as positively charged as ribonuclease. Antibacterial activity of various leukocyte fractions and cationic proteins was determined in vitro for Enterobacter aerogenes strain 2412-2. Antibacterial activity of various preparations was proportional to amount of test material present and varied inversely with number of bacteria in the test system. Comparative evaluations revealed that the neutrophil granule fraction had greater antibacterial activity than the whole cell homogenate or individual cationic proteins. Among cationic proteins, band 1 had the highest antibacterial activity, band 2 had the lowest, and band 3 had intermediate antibacterial activity. Cationic protein bands 4, 5, and 6 exhibited growth stimulatory rather than a growth inhibitory activity.