The immunological responses and mechanism of maternal immunity in Mycoplasma pneumoniae infection of mice were investigated.ICR female mice, 4 weeks old, and infant mice, 2 to 4 days old, were infected with M. pneumoniae. Anti-M. pneumoniae antibodies in serum and colostrum were determined by enzymelinked immunosorbent assay. The specific IgG antibody production persisted for 9 months or longer in both the young and infant mice. These infected mice were protected from rechallenge with M. pneumoniae. In addition, the infected dams conferred passive immunity on their offspring.The infant mice born to uninfected normal dams were protected from the challenge with M. pneumoniae when fed by infected foster dams.Conversely, the infant mice born to infected ,dams were not protected from the challenge with M. pneumoniae when the infants were fed by uninfected dams. The specific IgG antibody appeared in serum of infant mice inoculated orally with M. pneurnoniae-infected mouse serum and the infants were protected from challenge with M. pneumoniae, while the infants given protein A-absorbed serum were not protected from the challenge. These results suggest that one of the factors involved in the resistance of infant mice to M. pneumoniae infection is the specific IgG antibody present in the colostrum rather than the result of transplacental transfer.

The basic studies on detection and titration of the 60-kDa cross-reacting protein antigen (CRPA), which is common to gram-negative rods, by reversed passive gelatin agglutination test with monoclonal and polyclonal antibodies were performed. The gelatin particles sensitized with 500 micrograms/ml of the monoclonal antibody had an ability to react with 200 ng/ml of the purified CRPA for 1.5 h. In contrast, the particles sensitized with 200 micrograms/ml of the polyclonal antibody had an ability to react with 25 ng/ml of the purified CRPA for 1.5 h. In addition, the detection of the 60-kDa CRPA in urinary tract pathogens, which consisted of 60 bacterial strains representing 14 species, was carried out by using the gelatin particles sensitized with 200 micrograms/ml of the polyclonal antibody. The CRPA was detected in all gram-negative rods of urinary tract pathogens, but not in gram-positive cocci. These results suggested that the detection of the 60-kDa CRPA by reversed passive gelatin agglutination test was a rapid and simple method for screening gram-negative bacteriuria.