Serologic responses of children with meningitis due to Haemophilus influenzae type b.

The immunologic responses of 100 children hospitalized with meningitis due to Haemophilus influenzae type b were measured by the bactericidal antibody assay (BAA) and radioimmunoassay (RIA) for detection of antibody. Short-term (14-17 days after onset of illness) responses were detected by RIA alone in 20 children, by BAA alone in six, and by both tests in 23. The more sensitive RIA detected 20 children who would have been labeled "immunologically unresponsive" had only BAA been used. The magnitude of the antibody response was clearly related to age. Of 26 children with no immediate antibody response, 11 still had no rise in titer of antibody when restudied two to 20 months later; the remaining 15 had subsequent increases in titer. Nine of 10 children who showed an immediate antibody response remained positive when additional blood smaples were taken two to 18 months later. Over half of the children initially unresponsive to H. influenzae type b meningitis subsequently developed specific antibodies. The remainder, who failed to acquire detectable antibodies at either the acute stage of illness or late in convalescence, deserve further investigation as to the nature of their immunologic hyporesponsiveness to H. influenzae type b meningitis.