Two antigens, probably polysaccharide in nature, were extracted from smoothgonococci.
One of these could be adsorbed on to red cells and sensitized these cells to the action of a gonococcal antiserum. The factors concerned in this adsorption were investigated. The antigen, which was shown by a mirror absorption technique to be of two distinct types, was lost with the S-R change.
The second antigen was detected by its ability to fix complement in the presence of an immune serum.
It is suggested that these two antigens form a complex which determines the nature of the surface of the smooth gonococcus.
I wish to thank Dr J. C. Thomas, Provincial Pathologist, for the facilities for carrying out these investigations; Prof. M. van den Ende and Dr A. Kipps for helpful and constructive criticism; and Miss E. Bennett, Miss B. Jefferies, Mr L. Heitman, Mrs S. Maddison, and Mr G. C. Buckle for technical assistance.