Abstract
Summary A method for performing quantitative studies of Eaton's agent using a tissue culture system is described. The agent grew slowly in monkey kidney cell cultures, unlike many PPLO, but resembled other members of the genus Mycoplasma in being resistant to penicillin and sensitive to the tetracyclines. Demonstration of growth-inhibitory effects of both rabbit antiserum and sera of patients convalescent from atypical pneumonia, in confirmation of the work of Eaton, provides another parameter for studying immune response and relating Eaton's agent to human disease.