[Immunohistochemical study of lesions of temporal arteritis in Horton's disease].

Fourteen monoclonal antibodies were used to immunohistochemically label 22 temporal artery biopsy specimens taken from patients with temporal arteritis before treatment (n = 10), after 1.3 days of corticotherapy (n = 6) and after 12-30 days of steroids (n = 6). Histological sections from untreated patients revealed an inflammatory infiltrate comprised of approximately equal proportions of macrophages and T lymphocytes; the majority of the latter belonged to the CD4+ subset (the CD4+/CD8+ ratio varied from 2/1 to 4/1, depending upon the biopsy). These cells expressed high levels of HLA DR and low levels of interleukin-2 (IL2) receptors. A few B lymphocytes and plasmocytes were seen, mainly in the adventitia. Antigen-presenting cells (APC) were always found in the damaged media and natural killer cells (few in number) were sometimes present. Some macrophages were positively immunolabeled for IL6. A short, 1-to-3-day course of corticosteroids did not appreciably modify the lesions: cells remained highly activated, APC were seen in half the biopsies and IL6 immunolabeling persisted. The findings were essentially the same in treated but poorly controlled patients. Biopsies from 2 patients in clinical and biological remission revealed the persistence of an active immunological process. These observations indicate that the immunological process is poorly controlled by corticosteroid therapy.