Immunofluorescent studies of complement C3 in the hair follicles of normal scalp and of scalp affected by alopecia areata.

The deposition of complement C3 in the hair follicles of scalps of 4 normal subjects and of the affected parts of 9 patients with alopecia areata was found by the direct immunofluorescent methods. No deposition of immunoglobulins (IgG, IgA, IgM, IgD and IgE) was found. In the normal scalps, complement C3 was found to be deposited in the hyaline membrane of the hair bulb and in the internal layer of connective tissue sheath at the lower about 2/3 transient portion of anagen follicles, and in the thickened hyaline membrane of the catagen follicles. The deposition of complement C3 was also found in the anagen and catagen-like hair follicles even in the patients with alopecia areata, which was similar to the finding in the normal scalps. From the fact that the deposition of complement C3 was found chiefly in the transient portion of the hair follicles of the normal scalps, and that the behavior of deposition of complement C3 reflected the morphological state of hair follicles in each stage of the hair cycle, even in alopecia areata, complement C3 may be intimately related to the hair cycle, even though its significance is as yet unknown.