protein
Beta-2-microglobulin
Gene
B2M
Organism
Homo sapiens(9606)
Length
119 aa
Mass
13,715 Da
Beta-2-microglobulin (B2M) is a 119-amino acid component of the class I major histocompatibility complex (MHC) that plays a central role in antigen presentation to the immune system (UniProt: P61769). The protein facilitates the presentation of peptide antigens and is involved in immune surveillance; its surface export can be modulated by pathogenic factors such as mycobacterial proteins.
B2M is expressed broadly in tissues expressing MHC class I molecules. UniProt associations include immunodeficiency 43 (IMD43), characterized by reduced immunoglobulin and albumin levels, and hereditary systemic amyloidosis type 6 (AMYLD6), in which B2M variants form amyloid deposits affecting the gastrointestinal, cardiac, and nervous systems.
B2M is upregulated in Alzheimer's disease brain tissue. Analysis of post-mortem AD brain compared to age-matched controls using tandem mass tag proteomics across subcellular fractions showed a mean log2 fold-change of 0.64 (Chaparral AD proteomics), indicating modest but consistent elevation. This upregulation may reflect altered immune-inflammatory responses in the AD brain microenvironment.
Generated from the curated entity record below. May contain errors — verify against source links.
Proteomics Evidence · AD
↑ Up in ADP3
+0.635
P2
not detected
S2
not detected
S3
not detected
Mean log₂FC across detected fractions: +0.6351 (1 of 4 fractions detected)
Human post-mortem AD brain vs age-matched controls, TMT-labeled, 4 subcellular fractions (P2, P3, S2, S3), DDA proteomics.
Related Publications
Browse all →Tau molecular diversity contributes to clinical heterogeneity in Alzheimer's disease.
Dujardin Simon et al.Nature medicine2020PMID 32572268Deep Multilayer Brain Proteomics Identifies Molecular Networks in Alzheimer's Disease Progression.
Bai Bing et al.Neuron2020PMID 31926610A Multi-network Approach Identifies Protein-Specific Co-expression in Asymptomatic and Symptomatic Alzheimer's Disease.
Seyfried Nicholas T et al.Cell systems2017PMID 27989508Large-scale deep multi-layer analysis of Alzheimer's disease brain reveals strong proteomic disease-related changes not observed at the RNA level.
Johnson Erik C B et al.Nature neuroscience2022PMID 35115731Organization and regulation of gene transcription.
Cramer PatrickNature2019PMID 31462772
Function
Component of the class I major histocompatibility complex (MHC). Involved in the presentation of peptide antigens to the immune system. Exogenously applied M.tuberculosis EsxA or EsxA-EsxB (or EsxA expressed in host) binds B2M and decreases its export to the cell surface (total protein levels do not change), probably leading to defects in class I antigen presentation (PubMed:25356553)
Disease associations
Immunodeficiency 43IMD43
A disorder characterized by marked reduction in serum concentrations of immunoglobulins and albumin, and hypoproteinemia due to hypercatabolism. Patients may suffer from recurrent respiratory tract infections and severe skin disease.
Amyloidosis, hereditary systemic 6AMYLD6
A form of hereditary systemic amyloidosis, a disorder characterized by amyloid deposition in multiple tissues resulting in a wide clinical spectrum. AMYLD6 is mainly characterized by gastrointestinal and cardiac symptoms. Neurologic involvement, sicca syndrome, and carpal tunnel syndrome may also be present. Inheritance is autosomal dominant.
Sources
Last updated 5/8/2026, 6:25:59 AM