Somatic and "X" Agglutinins to the Salmonella Group.

IT has been recognized for some time that there may be cross-relationships between certain members of the Salmonella group due to the possession of minor somatic antigenic components which may not be constantly present. The importance of these relations was noted by Felix (1924) during his studies of the H and 0 agglutinins in enteric fever, in the course of which he observed that the non-specificity is such that somatic agglutinins produced during paratyphoid A or B infection are often more readily detected by means of a suspension of Bact. typhosum "0" 901 than by the homologous strain. He also noted that the antibodies formed in an individual infected with a given Salmonella strain may be less specific than those arising during the artificial immunization of the rabbit. This was also observed by White (1926) during his detailed work on the antigenic structure of the Salmonellas. He recorded "minor and variable cross-agglutination" between Bact. typhosum and Bact. paratyphosum B more evident in the sera of human cases than in the sera of rabbits which, he stated, are prone to form specific sera, agglutinins to the minor components of injected bacteria not appearing. Further knowledge of the extent and frequency of these relations would clearly be of value in the interpretation of the diagnostic agglutination test. The question also arises as to whether the so-called X antigen described by Topley & Ayrton (1924) has any bearing upon this problem. This antigen was first observed in suspensions of Bact. typhi-murium, Bact. newport and Bact. enteritidis which had been grown in broth for some days at 37? C., but has since been found to develop in almost all the Salmonellas. The X antigen is not specific for each type, so that there are obvious possibilities of crossagglutination where suspensions contain this antigen and sera contain the X agglutinin. Although we have extensive evidence in regard to the presence of agglutinins acting on the somatic antigen of Bact. paratyphosum B in the sera of patients infected with Bact. typhosum, and vice versa, and some evidence in regard to the presence of cross-agglutination between Bact. typhosum, Bact. paratyphosum A and Bact. paratyphosum B, we have almost no evidence with regard to the presence in cases of typhoid or paratyphoid fever of somatic agglutinins acting on other Salmonella somatic antigens. Nor have we any information with regard to the presence of X agglutinins in normal human