[B-cell anomalies in systemic lupus erythematosus]

Systemic lupus erythematosus is a non-organ-specific autoimmune disease characterized biologically by B lymphocyte hyperactivity and the production of autoantibodies directed against various cellular components, in particular nuclear antigens. Different strains of mice spontaneously develop a lupus-like disease and constitute a guidelight for human SLE. Both polyclonal B cell stimulation and clonal expansion induced by self-antigens participate in B cell hyperactivity observed in human and mouse SLE. B cells are hyperactive to various stimuli, in particular those delivered by T cells through surface molecules or cytokines. The consequences are an increased production of immunoglobulins and the development of autoantibodies thought to induce the major part of tissue lesions. B cells also participate in the pathological process as antigen-presenting and cytokine-secreting cells. An intrinsic defect of B cells is suspected to be responsible for B cell anomalies as illustrated by certain spontaneous murine models of SLE (motheaten mice) and by lupus-like syndromes observed in mice rendered deficient for genes controlling the B-cell receptor (BCR) signaling pathway. Genome wide scan analysis of various lupus strains allowed to identify several loci predisposing to lupus among which certain are associated with B cell hyperactivity suggesting that the intrinsic defect is inherited.