Subsequently, extensive sensitivity analyses verified the causal relationship between Treg cell-related immunophenotypes (CD25++ CD45RA- CD4 not regulatory T cell % T cell, CD25++ CD45RA- CD4 not regulatory T cell % CD4+ T cell, Secreting CD4 regulatory T cell Absolute Count and Activated & secreting CD4 regulatory T cell Absolute Count) and AD. Here, CD4 is linked to Alzheimer disease.