What you carry at this position in your DNA and what research says about it.
Multiple Sclerosis Risk: 8/10 evidence, 21 publications.
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Sample genotype (not yours): T/T
Higher Risk of Multiple Sclerosis and Leukemia
Elevated susceptibility to multiple sclerosis and chronic lymphocytic leukemia is associated with this profile. It also correlates with higher red blood cell counts but smaller cell volumes.
What this genotype means: Increased risk of multiple sclerosis; Increased risk of chronic lymphocytic leukemia; Higher red blood cell count with smaller cell volume.
Sample genotype (not yours): C/C
Typical Risk of Multiple Sclerosis and Leukemia
A typical baseline risk of multiple sclerosis and chronic lymphocytic leukemia is maintained with this profile. It also correlates with larger red blood cell volumes.
What this genotype means: Typical baseline risk of multiple sclerosis; Typical baseline risk of chronic lymphocytic leukemia; Larger red blood cell volume and typical count.
Sample genotype (not yours): T/C
Slightly Higher Risk of Multiple Sclerosis and Leukemia
A slightly increased susceptibility to multiple sclerosis and chronic lymphocytic leukemia is linked to this profile. It also leads to minor variations in red blood cell size and count.
What this genotype means: Slightly increased risk of multiple sclerosis; Slightly increased risk of chronic lymphocytic leukemia; Intermediate red blood cell count and volume.
Gene function and biological role
Gene Function: The ODF3B gene encodes a protein that is a component of the outer dense fibers of sperm tails. Although historically studied in the context of reproductive biology, recent genomic research has identified it as a novel immunogene with active roles in immune system function [1]. It is located on chromosome 22 in close proximity to other critical genes like SCO2 and TYMP, which are involved in cellular energy and metabolic pathways [2]. Variations in this genetic region are heavily linked to systemic immune-mediated conditions and the regulation of blood cell development [1] [2].
Variant Impact: The rs140522 variant is an upstream transcript variant located near the ODF3B gene. This genetic change acts as a regulatory marker that influences the expression of nearby genes involved in immune response and red blood cell production [1]. It is highly associated with alterations in several red blood cell measurements, including cell volume and hemoglobin levels [3]. Furthermore, it serves as a key genetic marker for susceptibility to autoimmune and hematological conditions [1] [3].
Key Insight: This variant acts as a shared genetic link between autoimmune susceptibility and the physical size of your red blood cells.
Location: ODF3B. Chromosome 22 · 22q13.33 · 50.5 Mb
Estimated prevalence by population
Global 14.7%; European 10.9%; African 25.7%; East Asian 8.6%; South Asian 10.5%; Americas 11.1%; Ashkenazi 9.7%; Finnish 8.6%; Middle Eastern 8.0%; Amish 5.9%.
Estimated TT genotype frequency.
Global 45.4%; European 44.2%; African 50.0%; East Asian 41.4%; South Asian 43.9%; Americas 44.4%; Ashkenazi 42.8%; Finnish 41.5%; Middle Eastern 40.5%; Amish 36.8%.
Estimated TC genotype frequency.
Global 39.9%; European 44.9%; African 24.3%; East Asian 50.0%; South Asian 45.6%; Americas 44.5%; Ashkenazi 47.5%; Finnish 49.9%; Middle Eastern 51.5%; Amish 57.2%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Immunity & Inflammation
Autoimmune Diseases
Multiple Sclerosis. Evidence: 8/10. Source: PMID 21833088. Increased Risk.
Cancer & Oncology
Blood Cancers
Leukemia. Evidence: 6/10. Source: PMID 28165464. Increased Risk.
Cardiovascular & Metabolic
Blood Cell & Iron Traits
Red Blood Cell Count. Evidence: 10/10. Source: PMID 27863252. Higher Count.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 23222517. Lower Volume.
Hemoglobin Levels. Evidence: 10/10. Source: PMID 37596262. Lower Levels.
Showing effects for C/C genotype
Multiple Sclerosis. Evidence: 8/10. Source: PMID 21833088. Typical Risk.
Leukemia. Evidence: 6/10. Source: PMID 28165464. Typical Risk.
Red Blood Cell Count. Evidence: 10/10. Source: PMID 27863252. Typical.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 23222517. Higher Volume.
Hemoglobin Levels. Evidence: 10/10. Source: PMID 37596262. Higher Levels.
Showing effects for T/C genotype
Multiple Sclerosis. Evidence: 8/10. Source: PMID 21833088. Slightly Increased.
Leukemia. Evidence: 6/10. Source: PMID 28165464. Slightly Increased.
Red Blood Cell Count. Evidence: 10/10. Source: PMID 27863252. Slightly Higher.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 23222517. Slightly Lower.
Hemoglobin Levels. Evidence: 10/10. Source: PMID 37596262. Slightly Lower.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
A moderately increased risk of developing multiple sclerosis, a chronic inflammatory disease of the central nervous system, is linked to this genetic profile [1]. Large-scale genome-wide association studies have identified the T allele as a key genetic risk factor for this autoimmune condition [1]. Susceptibility to chronic lymphocytic leukemia, a slow-growing cancer of the blood and bone marrow, is also higher with this profile [2]. On a cellular level, this variant influences red blood cell characteristics, leading to a higher overall red blood cell count but smaller individual cell sizes, known as mean corpuscular volume [3]. These hematological shifts are thought to reflect subtle differences in bone marrow activity and cell maturation pathways [3].
Increased risk of multiple sclerosis; Increased risk of chronic lymphocytic leukemia; Higher red blood cell count with smaller cell volume.
Sample genotype: CC (Homozygous)
A typical genetic baseline is represented by this profile, which carries zero copies of the risk-associated T allele. Standard, non-elevated risk of developing multiple sclerosis is expected for this group [1]. Protection against the increased risk of chronic lymphocytic leukemia associated with the T variant is also provided by this genotype [2]. In terms of blood composition, carrying two copies of the C allele is linked to larger red blood cell volumes, measured as mean corpuscular volume, and higher hemoglobin levels [3]. These characteristics indicate typical, healthy red blood cell development and oxygen-carrying capacity [3].
Typical baseline risk of multiple sclerosis; Typical baseline risk of chronic lymphocytic leukemia; Larger red blood cell volume and typical count.
Sample genotype: TC (Heterozygous)
A mild increase in the risk of developing multiple sclerosis compared to the typical baseline is associated with this heterozygous profile [1]. This variant is located near the ODF3B gene, which has been implicated in immune system regulation and inflammatory responses [1]. Research also indicates a slightly elevated risk for chronic lymphocytic leukemia, a type of blood cancer that affects B-lymphocytes [2]. In terms of blood morphology, this profile typically results in intermediate red blood cell counts and slightly smaller cell volumes [3]. These subtle changes in blood parameters are generally within normal physiological ranges and do not constitute a clinical disorder on their own [3].
Slightly increased risk of multiple sclerosis; Slightly increased risk of chronic lymphocytic leukemia; Intermediate red blood cell count and volume.
Variants with shared genetic architecture
rs3809627 · TBX6 Gene · Chr 16 · Spine and Immune Health
rs3811444 · TRIM58 Gene · Chr 1 · Red Blood Cell Traits
rs4672497 · Chr 2 · Red Blood Cell Metrics
Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis.
Multiple sclerosis genomic map implicates peripheral immune cells and microglia in susceptibility.
The Allelic Landscape of Human Blood Cell Trait Variation and Links to Common Complex Disease.
Content updated August 2026.
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