Systemic lupus erythematosus sera antilymphocyte reactivity: detection of antibodies to Tac-antigen positive T cell lines.

Sera obtained from patients with systemic lupus erythematosus (SLE) were tested for their reactivity to cell lines derived from cutaneous T-cell lymphoma (CTCL), or adult T cell leukaemia (ATL), and with other cell lines, by indirect immunofluorescence method. Approximately one half of SLE sera reacted with the surface antigens of HUT-102 cells, a cell line from CTCL, which constitutively expresses Tac antigen. The titre tended to be higher in the active than in the inactive stage. These positive sera also reacted with other neoplastic or normal T cell lines having Tac antigen. SLE sera reacting with HUT-102 surface antigens were further examined for their reactivities to Tac antigen, the putative IL-2 receptor, using HUT-102 or ATL-2. Pretreatment with anti-Tac monoclonal antibody partially blocked the reactivities to HUT-102 surface antigens in nine of 15 SLE sera tested. The binding of 125I-labelled anti-Tac monoclonal antibody was displaced by the addition of sera from six of 15 SLE patients. In addition, nine of the 15 SLE sera could inhibit the binding of 125I-labelled IL-2 to ATL-2 cells. These results suggested that some of SLE sera contained antibodies against the IL-2 receptor.