Notably, most AD risk variants in TREM2 are located in its second exon, which encodes the Ig-like V type domain—including sites of interactions between TREM2 and its ligands, such as the important AD-associated factors of ApoE, HDL, LDL, Aβ, and clusterin [5,26,30,31]. The gene discussed is TREM2; the disease is Alzheimer disease.