Natural Meningococcal Agglutinins and Lysins in Human Serum

Conclusions

Our data permit certain deductions regarding the nature and origin of the natural meningococcal agglutinin and lysin. It is clear that both antibodies increase in intensity and extensity with age and since conditions are generally favorable for the successive absorption from the nasopharynx of antigenic material belonging to the genus Neisseria one might be led to believe that both are due to "occult" immunization. However, as will appear below, it is more than likely that we are dealing with two separate entities.

The natural meningococcal agglutinin, according to our data, possesses a well marked immunological specificity. This is suggested not only by the occurrence of type-specific agglutinins in a certain percentage of normal human sera but more particularly by the fact that such agglutinins can be exhausted only by absorption with the specific antigens. In this respect the natural agglutinin resembles the immune agglutinin. Our observation that natural agglutinins occurred more often against group II-IV than against group I-III strains of meningococci is further suggestive evidence in favor of assuming their specific origin inasmuch as Branham 9 had found a preponderance of II-IV strains among cultures obtained from carriers whereas a majority of cultures isolated from cases of meningitis belonged to group I-III. In contrast to what has been said about the natural agglutinin, our data show that the power of normal human serum to lyse the meningococcus is invariably directed against both serological groups, and absorption-experiments revealed a complete lack of immunological specificity. The natural meningococcal lysin, therefore, appears to be quite different from the marked increase in meningococcidal power which is obtained following immunization with the specific organisms. This is also borne out by the fact that the lytic property in normal human serum may exist entirely apart from its agglutinating capacity. The conclusion, therefore, seems justified that the normal meningococcidal power of human and animal blood is wholly unrelated to any previous immunizing experience with the specific antigen. While the possibility cannot be excluded that in those instances in which natural agglutinin and lysin occur together both antibodies reflect the result of common antigenic stimulation, it is more than likely that this relationship is merely fortuitous and that their coexistence should be interpreted as a chance occurrence of 2 different substances, one a specific antibody and the other a nonspecific factor of the blood.