Increased number of OKT6-positive dendritic cells in the hair follicles of patients with alopecia areata.

In 6 patients with untreated alopecia areata in the progressive stage, 6 in the stationary stage, and 6 normal individuals as controls, an in situ analysis of OKT6-positive dendritic cells in hair follicles, and peribulbar and intrabulbar infiltrates was performed using the avidin-biotin-peroxidase method with monoclonal antibodies. In controls, OKT6-positive dendritic cells were distributed only in the upper portions of hair follicles and were not observed in the bulbar area, and the percentage of these cells among all epithelial cells of the hair follicles was 1.0 +/- 0.1% (mean +/- SE). In stationary-stage patients, the distribution and the percentage of positive cells were the same as those for the controls (1.1 +/- 0.1%). In the progressive stage, however, positive cells were distributed in both the upper portions of the hair follicles and the bulbar area, and the percentage of positive cells (4.9 +/- 0.3%) was significantly higher than that of controls. Staining for T, B lymphocytes and T cell subsets in the peribulbar infiltrates revealed a predominance of OKT4-positive cells (the OKT4/OKT8 ratio was from 3:1 to 4:1). This indicates that the number of OKT6-positive dendritic cells increases in the hair follicles of progressive alopecia areata and that these cells may play an important role in cooperation with T cells in the pathogenesis of alopecia areata.