 Since most sequence variation associated with immunoglobulins and T cell receptors are found in the CDRs, these regions are sometimes referred to as "hypervariable regions".Within the variable "domain", CDR1 and CDR2 are found in the variable (V) "region" of a polypeptide chain, and CDR3 includes some of V, all of diversity (D, heavy chains only) and joining (J) regions.CDR3 is the most variable.