Exploration of Immunology

Table 4. Clinical and immunological consequences of vitamin B12 deficiency [4, 19–21, 23–27].

Condition	Immune effect	Mechanism/Observations	References
Autoimmune diseases (multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus)	Reduced Treg numbers, impaired tolerance	FOXP3 hypomethylation; dysregulated Th1/Th2 balance	[4, 19, 20, 23]
Immunosenescence/Aging	Reduced T cell repertoire, decreased NK activity, poor vaccine response	Deficient vitamin B12 → impaired proliferation, elevated homocysteine	[4, 19, 21, 23–25]
Infectious diseases	Increased susceptibility to bacterial and viral infections	Impaired macrophage activation, reduced interferon production	[4, 19–21, 23, 25]
Chronic inflammatory diseases (diabetes, atherosclerosis)	Endothelial inflammation, oxidative stress	Elevated homocysteine; impaired nitric oxide (NO) metabolism	[4, 19–21, 23, 25]
Dysbiosis/Gut immune dysregulation	Altered SCFA production, Treg differentiation	Reduced beneficial microbiota, increased pro-inflammatory taxa	[21, 24–27]

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Summary of major clinical conditions associated with vitamin B12 deficiency and immunological consequences. FOXP3: forkhead box P3; NK: natural killer; SCFA: short-chain fatty acid; Treg: regulatory T cell.

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Acknowledgments

AI-Assisted Work Statement: During the preparation of this work, author(s) used ChatGPT for assistance in generating Figure 1. After using the tool, author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.

The authors wish to sincerely thank the patients and clinicians of the Strasbourg B12 research group (CARE B12) at the Hôpitaux Universitaires de Strasbourg (HUS, France) for their invaluable contributions to this study.

Author contributions

EA: Conceptualization, Investigation, Writing—original draft, Writing—review & editing. NLV: Conceptualization, Investigation, Writing—original draft, Writing—review & editing. TL: Validation, Writing—review & editing, Supervision. All authors read and approved the submitted version.

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The authors declare no conflict of interest.

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