Dual immunoglobulin light chain B cells: Trojan horses of autoimmunity?

Receptor editing, a major mechanism of B cell tolerance, can also lead to allelic inclusion at the immunoglobulin light chain loci and the development of B cells that coexpress two different immunoglobulin light chains and, therefore, two antibody specificities. Most allelically included B cells express two K chains, although rare dual-k cells are also observed. Moreover, these cells typically coexpress an autoreactive and a nonautoreactive antibody. Thus, allelically included B cells could operate like 'Trojan horses': expression and function of the nonautoreactive antigen receptors might promote their maturation, activation, and terminal differentiation into effector cells that also express and secrete autoantibodies. Indeed, dual-K B cells are greatly expanded into effector B cell subsets in some autoimmune mice, thus indicating they might play an important role in disease.