Immunodominance is the immunological phenomenon in which immune responses are mounted against only a few of the antigenic peptides out of the many produced.[1] That is, despite multiple allelic variations of MHC molecules and multiple peptides presented on antigen presenting cells, the immune response is skewed to only specific combinations of the two.[1] Immunodominance is evident for both antibody-mediated immunity and cell-mediated immunity.[2][3] Epitopes that are not targeted or targeted to a lower degree during an immune response are known as subdominant epitopes.[1][2] The impact of immunodominance is immunodomination, where immunodominant epitopes will curtail immune responses against non-dominant epitopes.[4] Antigen-presenting cells such as dendritic cells, can have up to six different types of MHC molecules for antigen presentation.[1] There is a potential for generation of hundreds to thousands of different peptides from the proteins of pathogens.[1] Yet, the effector cell population that is reactive against the pathogen is dominated by cells that recognize only a certain class of MHC bound to only certain pathogen-derived peptides presented by that MHC class.[1] Antigens from a particular pathogen can be of variable immunogenicity, with the antigen that stimulates the strongest response being the immunodominant one. The different levels of immunogenicity amongst antigens forms what is known as dominance hierarchy.[2]