Microbial community is highly diverse on the skin surface and can change in response to environmental challenges or aging. Its mutual relationship with the host and its key role in tissue homeostasis have also been reported. Previously, our workgroup described a non-inflammatory Th17/Treg milieu in sebaceous skin region which can be connected to the different microbiome and chemical milieu of this area. Since these factors also differ in apocrine gland-rich (AGR) areas, we aimed to compare the immune milieu of healthy sebaceous gland-poor (SGP) and AGR skin regions and to study its changes in Hidradenitis Suppurativa (HS), an inflammatory disease characteristically localized on AGR areas. 
Cytokines, cell surface markers, activation markers and transcription factors of keratinocytes, dendritic cells (DC) and T cells were detected by immunohistochemistry and qPCR in biopsies from healthy AGR and SGP skin and from HS lesional skin.  
In AGR skin, higher non-inflammatory TSLP expression, DC appearance without prominent activation and T cell presence with IL-17/IL-10 cytokine milieu were detected compared to SGP skin. The level of these parameters further increased in HS with the presence of activated DCs and a prominent influx of IL-17+ and IFN-γ+ cells. qPCR analyses of the aforementioned factors showed a similar pattern.
Similarly to sebaceous region, AGR skin areas represent distinct immune milieu from SGP regions, which can be the result of the different microbiome and chemical milieu. These changes may be connected to the maturation of apocrine glands and change in microbiome during puberty, but it needs further investigation.

Immune status of healthy apocrine gland-rich skin regions and its alterations in Hidradenitis Suppurativa