Detection of Antibody-Producing Cells of Mice Injected with Antigens of Neisseria meningitidis.

The technique of Jerne et al. was adapted to the study of the antibody response of mice to Neisseria meningitidis antigens. The mice were inoculated with heated group A bacteria or antigen concentrated from their culture fluid. Sheep erythrocytes were coated with bacterial lysate or culture fluid. These antigens were shown by immune hemolysis to be group-specific and appeared to be of identical specificity. The plaque-forming cell (PFC) response obtained with either antigen was dosedependent over a range of 10 to 300 mug per mouse. However, the maximum response, reached at 4 days, was quite low. The number of PFC per 10(6) nucleated cells, elicited by the heated bacteria and culture fluid, was 15 and 7, respectively. The number of PFC declined rapidly after the peak. A second injection of heated bacteria, given 18 days after the first injection, elicited a more rapid but otherwise similar reaction, apparently involving the production of only immunoglobulin M antibodies. No hemolytic antibodies were demonstrated in the sera of these mice. The passive hemolytic plaque assay here described provided the sensitivity necessary to study the details of the antibody response of mice to meningococcal antigen.