Immunogenicity of Mycoplasma pneumoniae

The immunogenicity of Mycoplasma pneumoniae for New Zealand white female rabbits was studied by using an immunization scheme which employed initial intramuscular immunization with vaccine in incomplete Freund adjuvant followed 3 weeks later by a series of five intravenous injections of fluid vaccine. Small doses of immunogen (15 to 150 mug of mycoplasmic protein per rabbit) gave rise to sera which contained antilipid complement-fixing antibody, produced one to three precipitin lines, but gave poor growth-inhibition on agar. Larger doses of immunogen (1.5 to 15 mg per rabbit) gave rise to sera which gave higher antilipid complement-fixing titers, four to eight precipitin lines, and good growth-inhibition. Doses smaller than 15 mug per rabbit failed to give rise to detectable antibody. Growth-inhibiting antibody was produced later than the other antibodies. The number of precipitin lines was controlled more critically by the quality of the antisera, as determined by the amount of immunogen, than by the quantity of serological test antigen. All sera which gave any precipitin lines produced a common precipitin line which stained for lipid.