Some autoimmune complications such as postinfectious encephalomyelitis are associated with immunologic abnormalities induced by measles virus infection. To address the superantigenic stimulation in measles which might be related with autoimmune complications, T-cells bearing the TCRBV5S2 or TCRBV8 chains and the expression of activation markers were analyzed by monoclonal antibodies. To estimate clonal expansions, the CDR3 length profile in T-cells bearing the TCRBV5S2 or TCRBV8 chains was analyzed by two-stage PCR. Results showed that the expression of DR molecules in CD3+ cells was increased significantly in measles patients (19.6 +/- 20.7%) compared to healthy children (2.9 +/- 1.4%). The mean percentage (7.1 +/- 4.4%) of T-cells bearing the TCRBV8 chain was increased in measles patients compared to healthy children (5.6 +/- 3.1%). The percentage of T-cells bearing the TCRBV5S2 chain in measles patients (3.0 +/- 1.2%) was similar to that in healthy children (2.7 +/- 0.6%). By analysis of the CDR3 length we found that there was no evidence of clonal expansions in T-cells bearing the TCRBV8 chain and that there were clonal expansions in T-cells bearing the TCRBV5S2 chain. These data suggest a conventional antigenic stimulation with T-cells bearing the TCRBV5S2 chain and a superantigenic stimulation with T-cells bearing the TCRBV8 chain may occur in the acute stage of measles infection.