Immunoglobulin heavy chain variable region third complementarity-determining region (CDR-H3)

The immunoglobulin heavy chain variable region third complementarity-determining region (CDR-H3, HCDR3) is a highly diverse polypeptide segment within the variable domain of the heavy chain of antibodies. It is formed by V(D)J recombination, incorporating sequence from variable (V), diversity (D), and joining (J) gene segments, with additional junctional diversity generated during B cell development[2][3][1]. CDR-H3 constitutes the central part of the antibody's antigen-binding site, and it is the most diverse region among all six antibody CDRs. This diversity underlies the enormous antigen recognition potential of the adaptive immune system, making CDR-H3 critical for the specificity and affinity of antibody-antigen binding[3][7][1]. In biomedical research and diagnostics, the sequence and length of heavy chain CDR3 regions serve as molecular fingerprints for B cell clonality and immune repertoire profiling, such as in lymphoma diagnostics or neutralizing antibody studies[4][6]. Summary: This entry refers to a functionally critical region of antibodies, not a discrete molecular target such as a receptor or enzyme, and should not be considered a canonical therapeutic target. The proper context for CDR-H3 is as a sequence feature within immunoglobulins, essential for antigen recognition, immune diversity, and as a molecular biomarker in immune profiling, but not itself an actionable therapeutic target.

Other names

CDR3 of heavy chainheavy chain CDR3HCDR3Ig heavy chain CDR3third complementarity-determining region of immunoglobulin heavy chain