Dandruff is a common scalp condition. The immune-microenvironment of dandruff scalp skin remains poorly characterised and the hair follicle’s physiological immune privilege (HF IP) status in dandruff is completely unknown. We hypothesised that the latter might be important in the context of dandruff-associated inflammation as the HF IP status is expected to impact on overall scalp skin immunophysiology. We analysed the expression of HF IP biomarkers (CD200, MHC class I, β2M, MHC class II) and HF IP guardians (α-MSH and MIF), and quantified intra- and perifollicular immune cells (CD4, CD8 and CD68) in healthy versus dandruff scalp (non-lesional and lesional) biopsies by quantitative immunohistomorphometry(n= 5-8). MHC Class I protein expression was increased in the proximal outer root sheath (ORS) of non-lesional and lesional dandruff HFs, while β2M protein expression was increased in the proximal ORS of lesional dandruff HFs and in the bulge of lesional dandruff HFs. CD200 expression was unaltered. The protein expression of the locally produced potent immunoinhibitory IP guardian, MIF, expression was decreased in the infundibulum, bulge, and proximal ORS of lesional dandruff HFs, while α-MSH expression was unaltered. Langerhans cells, labelled by intraepithelial MHC class II+ staining, were decreased in the infundibulum of lesional dandruff HFs (p<0.01). In lesional dandruff epidermis, CD4+ and CD8+ T cells were significantly increased (p<0.0001). The number of intra- and perifollicular CD68+ Macrophages, CD4+ and CD8+ T cells remained unchanged in dandruff scalp HFs. Together, this work presents the first evidence that dandruff is associated with a weakened HF IP, a reduction in the number of MHC class II+ Langerhans cells in the infundibulum, and epidermal infiltration of CD4+ and CD8+ T cells.

Dandruff is a common scalp condition. The immune-microenvironment of dandruff scalp skin remains poorly characterised and the hair follicle’s physiological immune privilege (HF IP) status in dandruff is completely unknown. We hypothesised that the latter might be important in the context of dandruff-associated inflammation as the HF IP status is expected to impact on overall scalp skin immunophysiology. We analysed the expression of HF IP biomarkers (CD200, MHC class I and β2M) and HF IP guardians (α-MSH and MIF), and quantified intra- and perifollicular immune cells (MHC class II+ Langerhans cells [LCs], CD4 and CD8) in healthy versus dandruff scalp (non-lesional and lesional) biopsies by quantitative immunohistomorphometry (n= 5-8). MHC Class I protein expression was increased in the proximal outer root sheath (ORS) of non-lesional and lesional dandruff HFs, while β2M protein expression was increased in the proximal ORS of lesional dandruff HFs. CD200 expression was unaltered. The protein expression of the locally produced potent immunoinhibitory IP guardian, MIF, was decreased in the infundibulum, bulge, and proximal ORS of lesional dandruff HFs, while α-MSH expression was unaltered. Langerhans cells, labelled by intraepithelial MHC class II+ staining, were decreased in the infundibulum of lesional dandruff HFs (p<0.01). In lesional dandruff epidermis, CD4+ and CD8+ T cells were significantly increased (p<0.0001). The number of intra- and perifollicular CD4+ and CD8+ T cells remained unchanged in dandruff scalp HFs. Together, this work presents the first evidence that dandruff is associated with a weakened HF IP, a reduction in the number of MHC class II+ Langerhans cells in the infundibulum, and epidermal infiltration of CD4+ and CD8+ T cells.

ESDR584 - Dandruff is associated with perturbations of hair follicle immune privilege, and the infundibular and epidermal immune microenvironment

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.