Immunological paralysis to pneumococcal polysaccharide in man.

A 9-month-old infant had severe pneumococcal meningitis and for the next two years showed immunological paralysis to the causal serotype. He remained normally responsive to a protein antigen (tetanus toxoid) and to polysaccharide antigens (Haemophilus influenzae type b capsule and pneumococcal capsule antigens other than the infecting/paralysing serotype). By the fourth year of life the child was spontaneously producing antibody to the infecting/paralysing pneumococcal serotype, at which time rechallenge with the previously tolerising antigen resulted in a secondary response. The occurrence of pneumococcal immunological paralysis in man is therefore validated.