Seroconversion of patient 96/2 against streptococcal superantigens (SAgs). Peripheral blood lymphocytes were stimulated with various recombinant streptococcal SAgs in the presence of serum 96/2–4, 96/2–10, or fetal calf serum only. The columns show the percentage of inhibition of recombinant SAgs by neutralizing antibodies in patient serum samples. The sequential serum on day 3 showed a complete lack of neutralizing antistreptococcal mitogenic exotoxin (SME) Z antibodies, while serum 96/2–10 con