Impaired T-cell-independent B-cell maturation in systemic lupus erythematosus: coculture experiments in monozygotic twins concordant for Klinefelter's syndrome but discordant for systemic lupus erythematosus.

In a case of monozygotic twins discordant for systemic lupus erythematosus (SLE), coculture experiments with isologous (i.e., genetically identical) lymphocytes were performed. Adequate T-helper-cell function in the SLE twin was demonstrated. Lack of B-cell responsiveness to T-cell-dependent and T-cell-independent polyclonal activators points to a T-cell-independent B-cell maturation defect in the SLE twin.