Five T-cell clones reactive to autologous HTLV-I-infected T-cells (KODA-TV) were established from peripheral blood lymphocytes of a HAM/TSP patient (KODA) by the limiting dilution method. All the clones showed CD3+, CD4+ and CD25+ surface markers and expressed alpha beta+ T-cell receptors to recognize KODA-TV antigens. One of the five T-cell clones (KODA-408) was infected with HTLV-I but the remaining four clones (KODA-400, 404, 405 and 409) were free of HTLV-I infection. KODA-408 recognized both KODA-TV and spinal cord antigens, the latter being extracted from autopsy tissues of a HTLV-I seronegative donor. KODA-408 did not recognize either alloantigens of peripheral blood mononuclear cells extracted from unrelated HTLV-I seronegative donors or purified human myelin basic protein. KODA-408 T-cell clone produced a considerable amount of TNF-alpha, IFN-gamma, and IL-6. The CDR3 motif of KODA-408 T-cell receptor showed a unique sequence CASSAGQS of v beta 8-D beta-J beta 1.5. These results indicated that HAM/TSP CD4+ T-cells were polyclonally activated by HTLV-I infection and antigenic stimulation. The T-cell repertoire shaped by HTLV-I infection included T-cells which recognized HTLV-I-infected T-cell antigens as well as spinal cord antigen in particular.