Immunopathogenesis of Takayasu arteritis

Takayasu arteritis is a common cause of renovascular hypertension in India. Sensitization to infective agents, particularly mycobacterium tuberculosis or autoimmune disturbances have been incriminated in its pathogenesis. Twenty patients of Takayasu arteritis along with groups of normal individuals, patients of essential hypertension, autoimmune disorders, tuberculosis, and healthy tuberculin reactors were studied. Besides detailed immunological profiles including LE cell phenomenon, serum complement C3 levels, antibodies to single (SS) and double stranded (DS) DNA, rheumatoid factor, lymphocyte subsets, blast transformation to antigens including, phytohemagglutinin, PPD, pokeweed, and purified human aortal antigen (PHAA) were examined. Soluble protein from human aorta was fractionated into 9 peaks by DEASE-52 and Sephadex G-75 chromatography, and 25 micrograms of major protein fraction-II was used for blast transformation study. Blast transformation by PHAA was higher in Takayasu arteritis as compared to all other groups (P < 0.05). Blast transformation to PPD showed wide variation in all the groups, and was significantly higher only in tuberculin reactors as compared to controls. These observations support aortal sensitization to PHAA playing a role in pathogenesis of Takayasu arteritis and do not relate tuberculosis to Takayasu arteritis, at least immunologically. In addition, the ratio of CD-4 positive to CD-8 positive lymphocytes changing in favor of the former and the concomitant increase in B lymphocytes favor the presence of autoimmune disturbances in Takayasu arteritis.