Total serum IgM and IgG agglutinins to P. acnes and neutralizing antibodies to P. acnes lipase, hyaluronate lyase and acid phosphatase were measured in normal individuals of different age groups. Agglutinins to P. acnes were detected in infants at 4 months of age and were present at a high level throughout life. A switch from predominantly IgM agglutinins in children, to IgG agglutinins in adults, occurred during adolescence. Anti-P. acnes lipase antibodies were present in 20% of teenagers and 17–42% of adults. Anti-P. acnes hyaluronate lyase antibodies were found in adults only (4–17%). Antibodies to acid phosphatase were not detected.
Agglutinins to P. acnes were measured in individuals with mild, moderate and severe acne, and in normal controls. Only patients with severe acne had significantly higher titres than the controls. IgM and IgG agglutinins were determined in 13–14-year-olds with mild, moderate and severe acne, and in normal controls. Thirty-three per cent, 60% and 100% of the acne patients, respectively, but none of the normal controls, had predominantly IgG agglutinins. No difference in the prevalence or titre of antibodies to P. acnes exocellular enzymes was observed when patients with severe acne were compared with normal controls.
There was no evidence to suggest a role for antibodies to P. acnes exocellular enzymes in the initiation of inflammatory acne.