Unexpectedly high frequency of antibody to Mycoplasma pneumoniae in human sera as measured by sensitive techniques.

Mycoplasmacidal and radioimmunoprecipitating antibodies to Mycoplasma pneumoniae were commonly detected in healthy children younger than five years of age, in whom natural disease due to M. pneumoniae is rare. Antibody in serum could also be demonstrated in Marine recruits several weeks or months before development of pneumonia due to M. pneumoniae. The latter observation suggests that serum antibody does not confer protection against disease caused by M. pneumoniae.