Immunohistochemical Characterization of the Cellular Infiltrate in Severe Alopecia Areata Before and After Minoxidil Treatment

The study investigated the effects of minoxidil on severe alopecia areata (AA) in 47 patients, with 36 showing positive responses to topical minoxidil 5% treatment. These responders experienced normalization of hair follicle characteristics and a shift in T cell populations from the skin to the peripheral blood. In contrast, nonresponders did not exhibit these changes. Further treatment with oral minoxidil in 34 patients did not alter T cell counts but significantly reduced perifollicular Langerhans and activated T cell counts, and nearly reduced monocyte counts. The findings suggested that minoxidil might alter follicular chemoattractive stimuli and have direct immunomodulatory effects on T cells, contributing to hair regrowth in AA.