Human antibody response to lipopolysaccharides from Neisseria gonorrhoeae.

Red cells coated with lipopolysaccharides from three different strains of Neisseria gonorhoeae have been used as antigens in a haemagglutination test for gonococcal antibodies. For each strain the geometric mean titre in sera from 50 male and 25 female patients was significantly higher than that in 50 normal controls. The most useful smooth strain, G1, picked out 84% of females and 46% of males from a group of patients known to have gonorrhoea, but only gave 2% positives among controls. The rough strain, G2, gave 10% positives in controls and 31% in patients. The results suggest that the method is worth developing further as a diagnostic test and that strain differences are important. False positives were probably due to cross-reacting antibodies.