Cellular immunity in patients with meningococcal disease and in vaccinated subjects.

Cell-mediated immunity was studied in patients with group A meningococcal meningitis and in normal subjects given group A meningococcal vaccine. Lymphocytes responsiveness to phytohaemagglutinin and to meningococcal antigens was markedly depressed in patients with acute meningococcal infection. This defect was present when lymphocytes were cultured in autologous or foetal calf serum. Patients also showed a transient increase in the degree of inhibition produced by whole group A meningococci in leucocyte migration assays. Meningococci of other groups produced a similar degree of inhibition. Vaccination with group A meningococcal polysaccharide vaccine had no effect on lymphocytes responsiveness to meningococcal antigens or on the inhibitory effect of group A meningococci on leucocyte migration.