Migration inhibition of peritoneal macrophages by peptidoglycan

Previous studies have shown that peptidoglycans from group A and B streptococci inhibit the migration of peritoneal exudate cells from non sensitized rats and guinea pigs. In the present studies peptidoglycans from S. aureus and S. epidermidis were found to inhibit the migration of cells to the same extent as group A streptococcal peptidoglycan. In contrast, HSA pentapeptide, an immunologically active synthetic analog of the peptide moiety of peptidoglycan which is free of the intrinsic toxicity of naturally occurring peptidoglycans, did not induce migration inhibition of peritoneal exudate cells from non sensitized guinea pigs. Sensitization of animals with 200 μg HSA pentapeptide emulsified in incomplete Freund's adjuvant significantly reduced the inhibitory effect of streptococcal and staphylococcal peptidoglycan; HSA pentapeptide again showed no activity. However, when HSA pentapeptide was tested against cells from animals sensitized with 200 μg HSA pentapeptide incorporated in complete Freund's adjuvant, a strong inhibition of migration was evident. Skin tests performed in these animals in contrast to the dermonecrotic reaction elicited by streptococcal or staphylococcal peptidoglycan, revealed a characteristic delayed hypersensitivity to HSA pentapeptide.