MHC class II antigen presentation

The pathway list, the hierarchy and the genes on this page are read from the files Reactome publishes for Reactome release 97, built into this site on 2026-09-09: the pathway list, the hierarchy relationship file and the two gene mapping files. The record card is the one live read, Reactome's own record of this pathway.

Reactome's download page describes the mapping files: Mapping files link the source database identifier to the lowest level pathway diagram or subset of the pathway, all levels of the pathway hierarchy or database identifier to all reactions. [R13] The gene list here is the all-levels mapping of NCBI Gene ids, filled from the all-levels mapping of Ensembl ids where the NCBI file has no row for a gene; each row names which file it came from by the shape of its source id. Each row carries the evidence codes the file writes for it, as written and unranked, and both where the file writes both; no page of Reactome's documentation the survey read defines the codes, so this page does not expand them. A gene id the identity files do not name is kept as the source's own id with no door rather than turned into a symbol.

Every rat pathway in Reactome is inferred from the curated human one: We use the set of manually curated human reactions to electronically infer reactions in fourteen evolutionarily divergent eukaryotic species for which high-quality whole-genome sequence data are available, and hence a comprehensive and high-quality set of protein predictions exists. [R11] Reactome's own sentence about what that produces is printed beside the record: The electronically inferred reactions presented in Reactome are thus not data, but hypotheses useful to direct the design of confirmatory experiments. [R11]

On citing what a search finds, Reactome says: It should be remembered that while we strive to contain the most current and accurate data, Reactome should not be used in citations where other primary sources of information are available. [R12] The record card prints the literature Reactome attaches to a curated pathway for that reason. The data are public domain: All data in the Reactome database and files derived from that data are licensed under the Creative Commons Public Domain Dedication (CC0). User may copy, modify, and distribute these data, even for commercial purposes, without asking for permission. Attribution is encouraged but not required. [R10] The pathway illustrations are licensed apart, under CC BY 4.0, and none is shown here.

A gene on this list is one Reactome places in this pathway in this release, and that is all the row says: it does not say the gene is expressed in a tissue or associated with a disease, which are the other two explorers' questions, read from other sources. Reactome's papers of record are [R01] [R02].

1. [R01] Ragueneau E, Gong C, Sinquin P, Sevilla C, Beavers D, Grentner A, et al. (2026). The Reactome Knowledgebase 2026. Nucleic Acids Research 54:D673-D681. PMID 41251150, doi 10.1093/nar/gkaf1223.
2. [R02] Milacic M, Beavers D, Conley P, Gong C, Gillespie M, Griss J, et al. (2024). The Reactome Pathway Knowledgebase 2024. Nucleic Acids Research 52:D672-D678. PMID 37941124, doi 10.1093/nar/gkad1025.
3. [R10] Reactome, reactome.org. License Agreement. https://reactome.org/license, read 2026-09-09.
4. [R11] Reactome, reactome.org. Computationally inferred events. https://reactome.org/documentation/inferred-events, read 2026-09-09.
5. [R12] Reactome, reactome.org. Citing us. https://reactome.org/cite, read 2026-09-09.
6. [R13] Reactome, reactome.org. Download. https://reactome.org/download-data, read 2026-09-09.