CD4 and acne: Activation of mast cells to produce IL-17 in CD4 + T cell rich areas has been suggested, even in the subclinical stages of acne (Eliasse et al., 2021), and scattered distribution of IL-17A positive cells was observed in both the papillary dermis and around sebaceous follicles in acne lesions (Kelhälä et al., 2014).