Table 5.

Summary of abnormal immune responses and immunoregulation in patients with SLE

Hyperactivated B cells Number of activated B cells producing Ig increased in peripheral blood B cell abnormalities are present in unaffected family members and may precede SLE development Lupus B cells are more prone to polyclonal activation by specific antigens Raised IL-6 and IL-10 concentrations may promote B cell hyperactivity B cell responses to activating signals are abnormal

Hyperactivated T cells Number of activated T cells increased in peripheral blood Abnormal early events of T cell activation T cell function skewed towards B cell help and Ig production Lupus T cells produce little IL-2 on stimulation

Abnormal phagocytic functions Phagocytic cells cannot bind or process immune complexes efficiently Phagocytosis of apoptotic cells impaired

Abnormal immunoregulation Defective clearance of immune complexes and apoptotic materials because of qualitative or quantitative defects of early complement proteins (C2, C4, C1q), Fcγ, CR1, and C1q receptors on cell surfaces Suppressive activity of suppressor T cells and NK cells on activated T and B cell network is inadequate Idiotypic control of antibody production is dysregulated

Ig, immunoglobulin; IL, interleukin; NK, natural killer; SLE, systemic lupus erythematosus.