Immune Microenvironment of Hair Follicles in Tumor Immunotherapy

Bo Li,1,* Sitong Jiang,2,* Fan Yang,3 Min Tang,2 Haozhen Lv,1 Lin Li,2 Jianmin Chang1 1Department of Dermatology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China; 2Department of Medical Oncology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, People’s Republic of China; 3Department of Medical Oncology, Senior Department of Oncology, The Fifth Medical Center of PLA General Hospital, Beijing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jianmin Chang, Email [email protected] Lin Li, Email [email protected]: Although tumor immunotherapy has shown significant efficacy against solid tumors, it frequently causes cutaneous and follicular adverse events resulting from disruption of the hair follicle immune microenvironment. This microenvironment is maintained through careful regulation by immune cells and cytokine networks to support normal hair cycling. Immune checkpoint inhibitors disturb this balance by activating T cells, promoting macrophage polarization toward pro-inflammatory phenotypes, upregulating inflammatory cytokines such as tumor necrosis factor-alpha, and activating Toll-like receptor/nuclear factor-kappa B signaling pathways, ultimately leading to follicular toxicity including alopecia. Encompass relies mainly on topical corticosteroids and other immunomodulatory agents. A deeper understanding of these mechanisms is essential to identify key regulatory nodes for future targeted interventions.Keywords: immune microenvironment, hair follicles, tumor immunotherapy