TNF and Alzheimer disease: Individuals sensitized to alpha-gal also showed increased expressions of the genes CDKN1A, TNF, CXCL2, CCL3, and CCL3L1. CDKN1A, also known as the p21 cell cycle inhibitor [55], and TNF have been identified as pivotal proteins in atopic dermatitis (AD) pathogenesis through a review of AD-associated protein–protein interaction networks, with some suggesting a role for these proteins in the development of itch and xerosis [56].