Recent progress in the understanding of B-cell functions in autoimmunity

Our early concepts of the normal role of B cells in immunity focused on the ir ability to produce antibodies (Ab) and in the case of autoimmune disease s autoAbs, some of which were pathogenic. Over the past 10 years, it has be came apparent that B cells display a variety of characteristics, other than Ab production, which could contribute to autoimmunity. They normally play a role in the development of lymphoid architecture, regulating T-cell subse ts and dendritic cell (DC) function through cytokine production, and in act ivation of T cells. Receptors editing is also important in B cells which ai ds in immunity to infection and, possibly, prevention of autoimmunity. Tran sgenic animal models have now shown that B cells are necessary for many aut oimmune diseases although their Ab products are not required in some cases. Negative signalling by CD5 and other molecules, such as CD22, in maintaini ng tolerance through recruitment of slr-homology two domain-containing prot ein tyrosine phosphatase-1 has also been documented. In fact, we have now r eached a new era whereby the B cell has returned as an important contributo r to autoimmune disorders, so that the race is on to characterize signallin g regulation via the B-cell receptor and coreceptors. identification of suc h molecules and their potential defects should lead to effective ways of co ntrolling the immune response and in particular preventing the development of autoimmune states. The classical view of B cells in the biology of immun e responses to infectious and self-antigens (Ag) that they promote immunity primarily by producing Ab turns out to be rather naive. Indeed, studies ov er the last few years indicate that this view is far from complete, and sug gest that B lymphocytes have extraordinarily diverse functions within the i mmune system. Furthermore, it is becoming increasingly clear that the patho genesis of autoimmune diseases cannot solely be accounted for by T cells, a nd intrinsic abnormalities of B cells have been described in such condition s. Ln this brief review we highlight some recent observations in the contex t of B lymphocyte in pathophysiology, and focus on their revival as pivotal players the pathophysiology in autoimmune diseases. Yet, it remains diffic ult to provide a model of how important B cells are in immunity and autoimm unity.