Hair follicles (HFs) enjoy a relative immune privilege (IP) that is characterized by downregulation of major histocompatibility complex (MHC) class I and local expression of potent immunosuppressants. Normally, natural killer (NK) cells attack cells with absent/low MHC class I expression. However, because few perifollicular NK cells are found around healthy human anagen HFs, we asked how HFs escape from NK cell attack. This study suggests that this happens via an active NK cell suppression. Alopecia areata (AA), an organ-specific autoimmune disease thought to result from a collapse of HF-IP, in contrast, shows striking defects in NK cell inhibition/containment. We show that the NK cell inhibitor macrophage migration inhibitory factor is strongly expressed by the HF epithelium, and very few CD56(+)/NKG2D(+) NK cells are observed in and around normal anagen HFs compared to AA with prominent aggregations of CD56(+)/NKG2D(+) NK around AA-HFs. By flow cytometry, many fewer NK function-activating receptors (NKG2D, NKG2C) and significantly more killer cell Ig-like receptors-2D2/2D3 were found to be expressed on peripheral blood CD56(+) NK cells of healthy controls than on those of AA patients. In addition, only weak immunoreactivity for MHC class I chain-related A gene was observed in normal anagen HFs compared to AA. To our knowledge, this defect is previously unreported and must be taken into account in AA pathogenesis and its management.

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Wound compression and fixation are important to reduce scarring. Numerous postoperative treatments have been developed to reduce scar formation; however, a simple and effective device that improves the appearance and histochemical properties of incisional scars is needed. Therefore, the authors have devised a novel method, negative-pressure fixation, that applies negative pressure inside polyurethane foam covered with film. In the present study, negative-pressure fixation was applied to incisional wounds resulting from the insertion of a tissue expander in patients undergoing two-stage breast reconstruction. The authors aimed to evaluate the effects of negative-pressure fixation on scar appearance and histochemical properties in comparison to those for film dressing without negative pressure. A prospective, open-label, randomized, single-center study was performed. A half-side test was conducted on the incisional scar resulting from tissue expander insertion during breast reconstruction after mastectomy in 13 female patients. The dressings on both sides of the scar were replaced once per week until the tissue expander was adequately inflated. The outcomes were assessed 6 months later. Scars were photographed before the second operation and were evaluated using a visual analogue scale. All scars were removed and resutured during the final operation, allowing a histochemical analysis. The mean visual analogue scale score for the negative-pressure fixation side was significantly lower compared with that for the film dressing side (p = 0.0025). In addition, the scar on the negative-pressure fixation side was significantly narrower (p = 0.0015). Thus, negative-pressure fixation is a simple and effective device for improving the appearance and histochemical properties of incisional scars.