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The immune response of experimentally infected hamsters and human patients to Mycoplasma pneumoniae was examined by radioimmunoprecipation in conjunction with gel electrophoresis and fluorography. Both intrinsically and extrinsically labeled mycoplasma proteins were coincubated with acute and convalescent sera in a radioimmunoprecipitation assay. Two M. pneumoniae proteins were selectively precipitated by convalescent sera. These predominant immunogens were trypsin-sensitive, antibody-accessible surface proteins that co-migrate on polyacrylamide gels with proteins P1 and P2, which were previously implicated by us as mediators of cytadsorption. Anti-M. pneumoniae antiserum did not precipitate radiolabeled antigens derived from Mycoplasma orale or Mycoplasma salivarium. These data indicate that M. pneumoniae infection stimulates a specific and highly targeted host antibody response to key proteinaceous immunogens.

Postoperative fever and pericardial-pleural reaction, designated postpericardiotomy syndrome (PPS), is a common complication of cardiac surgery involving entry into the pericardium. To determine whether the etiology of PPS is viral or immunologic, we undertook a prospective, triple-blind study of consecutive long-term survivors of intrapericardial surgery in the pediatric age group. We evaluated clinical evidence of syndrome and concurrent appearance of antiheart antibody (AHA) by indirect immunofluorescence and antiviral antibody (AVA) by complement fixation in sera preoperatively and serially postoperatively. Incidence of PPS was 27% overall in 400 subjects, but only 3.5% in infants younger than 2 years of age. AHA in high titer appeared in all patients with PPS. A fourfold or greater rise in titer to AVA was found in 70% of these but in only 5% of those with negative AHA and no PPS. AVA rise, tested in 280 consecutive patients, was to no single one of the eight viruses studied (adenovirus, cytomegalovirus, and coxsackievirus B 1-6). Instead, the rise and fall, consistent with antiviral response to a recent infection, was exhibited usually to one but occasionally to two or more viruses, and the viral prevalence changed from year to year, as did that in the community. The study suggests that concurrent fresh or reactivated viral illness plays a role in triggering the immunologic response that characterizes the PPS.

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