CCL17 and Alzheimer disease: The third category consists of spontaneous models, represented by the NC/Nga mouse strain, which develops pruritic skin lesions spontaneously at approximately 8 weeks of age under conventional housing conditions, exhibiting impaired water-retention properties and barrier dysfunction, reduced ceramide content, intrinsic susceptibility to AD-like dermatitis, and high expression of Th2-specific chemokines, including thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC), along with their receptor CCR4 in lesional skin (Zheng et al., 2024).