Difference in Immunohistochemical Characteristics Between Takayasu Arteritis and Giant Cell Arteritis: It May Be Better to Distinguish Them in the Same Age

This study aimed to compare Takayasu arteritis (TAK) with giant cell arteritis (GCA) through immunohistochemistry principally of inflammatory cells; these two disorders may be on the spectrum within a single disease state. Nine TAK and 5 GCA surgically resected vessel specimens were selected. TAK specimen was divided into each three acute-, chronic-, and healed-phase samples based on intimal and adventitial thickening. Immunohistochemical analysis was performed of smooth muscle cells and inflammatory cells including lymphocytes, plasma cells, macrophages, and dendritic cells, where three healed-phase TAK specimens were excluded due to paucity of inflammation. Immunopositive cells per three different fields in intima, media, and adventitia were counted in each specimen, and their numbers in these three layers along with total 3 layers were compared between the two disorders. Intimal smooth muscle maturity estimated by ratio of h-Caldesmon cells to α-SMA cells significantly increased in chronic- and healed- over acute-phase increases in TAK. Mann-Whitney tests demonstrated significantly more adventitial lymphoplasmacytic infiltration and less intimal fascin dendritic cells, as well as overall more CD8 T-cells, more CD20 B-cells and lower CD4/8 ratio in TAK than in GCA. Different inflammatory involvement is suggested in the pathogenesis of TAK and GCA.