immunodominant

Immunodominant describes epitopes that induce the strongest immune response within a given antigen. In adaptive immunity, responses tend to target multiple epitopes, but a subset becomes dominant, driving the majority of T cell or antibody activity. Immunodominant epitopes are frequently the primary targets of CD8+ cytotoxic T cells recognizing peptide-MHC class I complexes and of CD4+ helper T cells recognizing peptide-MHC class II complexes, as well as of B cell responses to certain epitopes. The remaining epitopes are considered subdominant or cryptic.

Several factors influence immunodominance. The affinity and stability of peptide binding to MHC molecules, the efficiency of antigen processing, and the abundance or accessibility of the antigen determine which peptides are presented to T cells. The T cell receptor repertoire and competition among epitopes for presentation also shape dominance. Host genetics, particularly HLA allele variation, strongly influences which epitopes are immunodominant. Immunodominance can facilitate pathogen control but can also enable immune escape if the dominant epitopes mutate, reducing recognition.

Implications for vaccines and immunotherapies are widely studied. Vaccines that emphasize immunodominant epitopes can produce strong responses but may limit breadth if other epitopes are ignored. Conversely, including subdominant epitopes or designing immunogens that alter epitope hierarchies can broaden protection. In research, immunodominance informs interpretation of immune assays and the design of vaccines, diagnostics, and therapies in infectious disease, oncology, and autoimmunity.