Dimerization of TCTP and its clinical implications for allergy

Following the detection of histamine-releasing activity (HRA) in the supernatants of peripheral blood mononuclear cell cultures, research efforts were directed at characterizing the source of this activity, mostly focusing, on IgE-dependent histamine-releasing factors (HRFs). HRF is now variously called translationally controlled tumor protein (TCTP), p21, p23, and fortilin. TCTP exhibits cytokine-like functions including release of histamine, induction of TH₂ cytokines and chemoattractants, augmentation of B cell proliferation, and immunoglobulin production during late phase allergic inflammation. Because of its association with the allergic status of patients, TCTP emerged as a potential key agent in the modulation of allergic diseases. Several lines of evidence suggest that TCTP exhibits its cytokine-like functions only after it is modified by the proteases, altered oxidant-antioxidant balance and immunoglobulin E, present in the inflamed sites. This review will try to show that dimerization is the critical modification of TCTP if not the only modification, responsible for its cytokine-like activity causing allergic diseases.