Reference materials were produced to standardize the immunoglobulin class specificity and potency of immunofluorescent anti-IgM conjugates used for diagnostic tests for congenital syphilis. In attempting to mimic essential immunologic characteristics of syphilitic and nonsyphilitic infant sera, we evaluated these sera in comparison with processed adult sera. We were quite surprised to discover that some syphilitic babies do not produce significant quantities to IgM antibody to T. pallidum in response to their infection, as would be expected; instead, they make relatively large amounts of IgM anti-IgG. We found this to be true also for newborns and infants infected with cytomegalovirus, rubella, and toxoplasmosis. To our knowledge, this observation has not been previously reported. However, it could have been predicted from the knowledge that older infants and young children normally produce IgM antibodies to maternal IgG allotypes (Gm factors). We are disturbed that these findings suggest that currently recommended indirect immunofluorescence IgM tests for perinatal infection may not be disease specific. Our observations may be important for a better understanding of basic immunologic mechanisms of fetal-maternal to tolerance and fetal response to life-threatening infection.

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Strains of gonococcus were shown to be immunologically heterologous. Serum bactericidal activity generally correlated with induced immunity to gonococcal challenge as detected by the guinea pig subcutaneous chamber model. Sera devoid of bactericidal activity reflected the lack of cross-protection in subcutaneous chambers. Factors affecting the bactericidal assay described in this report include (i) source of complement, (ii) concentration of test antigen and complement activity, and (iii) presence of calcium and magnesium ions and bovine serum albumin in diluent. Poor correlation was observed between agglutinating activity of the immune sera and protection.Knowledge of immunological properties of gonococcal strains is essential both for the understanding of gonococcal immunity and for the development of vaccines. Immunological diversity of nine strains of Neisseria gonorrhoeae was demonstrated by cross-protection in guinea pig subcutaneous chambers (4). Since the procedure described for immunotyping is elaborate and is not suitable for large-scale screening or typing of clinical isolates, attempts were made to correlate the results of immunotyping with those obtained by experimental serotyping procedures. Our results are presented in this report.MATERIALS AND METHODS Bacterial cultures. The nine strains of Neisseria gonorrhoeae used in this study were described previously (4).Gonococcal immune sera. Antisera for each of the nine gonococcal strains were prepared in Hartley strain guinea pigs weighing approximately 300 g each. The guinea pigs were injected weekly for 11 weeks by the subcutaneous route with type 1 (Ti) living cultures containing 109 colony-forming units (CFU). Blood was obtained by cardiac puncture with a 25-gauge needle from animals under light anesthesia.Bactericidal antibody assay. The appropriate gonococcal strains were grown on GC base (GCB) medium supplemented with IsoVitaleX (Baltimore Biological Laboratories, Baltimore, Md.) overnight at 37°C in a candle jar. Bacterial growth was suspended in glass tubes (13 by 100 mm) containing Trypticase soy broth (TSB) (30 g/liter of distilled water). The suspension was adjusted to an optical density of 0.5 units with a Leitz spectrophotometer at 535 nm and was then diluted 1:100 in TSB for use in the bactericidal assay. The diluted suspension contained approximately 10" CFU per ml.The diluent used throughout the assay was phosphate-buffered saline (PBS), pH 7.2, containing 0.006% MgCl2 6H20, 0.004% CaCl2 2H20, and 1% bovine serum albumin. Guinea pig complement (Texas Biologicals, Fort Worth, Tex., lot 507) or fresh chimpanzee serum was used. Complement preparations were pretested to determine that the bacteria used were not nonspecifically killed in the complement. Complement was stored at -70°C until used.All sera to be tested, including reactive and nonreactive controls, were heated for 30 min at 56°C. Serial twofold dilutions were made by using microtiter loops to transfer 0.025 ml of each serum and the controls to microtiter U-bottom plates (Ames, E...