Absence of tyrosinase-related protein-2/dopachrome tautomerase transcripts in PBMCs from vitiligo patients.

Tolerance is achieved by mechanisms occurring in both the thymus and periphery. Several reports have shown that presence of an antigen in the peripheral circulation results in tolerance induction. These reports imply that absence of a self-antigen can lead to induction of autoimmunity. Here, we show that tyrosinase-related protein 2 (TRP-2) transcript is not detected in the peripheral blood mononuclear cells (PBMC) of vitiligo patients but is detected in healthy controls. Our result indicates that probably due to lack of expression in the PBMC, TRP-2 is not available for induction and maintenance of peripheral tolerance in vitiligo patients. It is also reported by others that co-stimulatory molecules are required for the initiation of autoimmune diseases in experimental models. We therefore analysed the transcript levels of these costimulatory molecules in vitiligo patients and healthy controls. We observed that the transcripts of B7.2 and CD40 molecules are more or less similar in both patients and controls. We could not detect B7.1 in any of the human subjects. Thus, we conclude that the antigen presenting cells (APC) are not in an activated state and that constitutively activated APC are possibly not required for the progression of the disease once it has been initiated.