Immunofluorescence studies on complement components in the hair follicles of normal scalp and of scalp affected by alopecia areata.

The deposition of complement components (Clq, C4 C3, C5 and C9) and properdin in scalp hair follicles was examined by the immunofluorescence method in patients with alopecia areata and in normal subjects. C3, C5 and C9 were found deposited there. The complement deposition was most frequent in the case of C3 and less frequent in C9 and C5. There was no difference regarding deposition between normal subjects and patients with alopecia areata. No deposition of Clq, C4 or properdin was observed in the hair follicles of the scalp. These findings suggest a relationship between the hair cycle and the activity of C3 and its late complement components in the scalp.