Prevention of B cell clonal deletion and anergy by activated T cells and their lymphokines

B cell tolerance is described as the absence of a measurable antibody forming response to an antigenic challenge. The establishment of antigen-specific tolerance requires, by definition, engagement of the B cell antigen-specific receptor. However, only in some circumstances does this engagement lead to tolerance, while in others it produces B cell activation and secretion of immunoglobulins. Several mechanisms occur naturally in vivo abrogating the expression of deleterious autoantibodies and contributing to the state of self-tolerance. In this review, we will examine different ways in which B cell tolerance can be broken, focusing on evidence showing that activated-T cells and/or their lymphokines can prevent B cell clonal deletion and thus have a potential role in the pathogenesis of autoimmune diseases. This approach is based on the well-known association of several lymphokines, such as IL-1, IL-2, IL-4, IL-5, and type I interferons, with autoimmune phenomena in vivo.