Newborn rabbit alveolar macrophages are deficient in two microbicidal cationic peptides, MCP-1 and MCP-2.
Adult rabbit alveolar macrophages (AM) contain 2 cationic peptides with a broad spectrum of antimicrobial activity in vitro against bacteria, fungi, and some enveloped viruses. We determined the amounts of both peptides qualitatively in 1-day-old (1d), 7-day-old (7d), 21-day-old (21d), and adult rabbit AM and found that 1d AM were deficient in both peptides. The levels of MCP-1 extractable from AM were quantitated relative to known standards of purified peptides and were found to increase 6-fold between 1d and 21d AM. Adult AM yielded 9 times as much MCP-1 as did 1d AM despite nearly the same acid-extractable protein content per cell. Using immunoperoxidase techniques we showed that the deficiency of MCP-1 and MCP-2 involves 1d AM uniformly and that all AM 7 days or older have detectable MCP. Seven-day-old AM (and to a lesser extent 1d AM) incorporated 35S-cysteine into intracellular MCP in cell culture, indicating that AM actively synthesize these peptides. The deficiency of these antimicrobial substances may contribute to functional immaturity of newborn rabbit AM.
D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D023181:Antimicrobial Cationic Peptides; D006651:Histocytochemistry; D007120:Immunochemistry; D008264:Macrophages / Q000378:metabolism*; D011488:Protein Deficiency; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D011817:Rabbits
D023181:Antimicrobial Cationic Peptides