What you carry at this position in your DNA and what research says about it.
MBL Immune Protein: 8/10 evidence, 16 publications.
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Sample genotype (not yours): C/C
Typical MBL Protein Levels
This genotype is associated with normal, fully functional levels of mannose-binding lectin in the bloodstream.
What this genotype means: Standard innate immune defense; Typical circulating MBL levels.
Sample genotype (not yours): C/T
Reduced MBL Protein Levels
Carrying one copy of the variant allele leads to moderately reduced levels of functional immune protein.
What this genotype means: Moderately lower MBL levels; Potential protection against tuberculosis.
Sample genotype (not yours): T/T
Significantly Lower MBL Levels
Having two copies of the variant allele leads to a significant reduction in functional immune protein levels.
What this genotype means: Highly reduced MBL levels; Lower risk of tuberculosis infection.
Gene function and biological role
Gene Function: The MBL2 gene encodes mannose-binding lectin, a crucial pattern-recognition protein secreted by the liver into the bloodstream [1]. This protein plays a key role in the innate immune system, the body's first line of defense against invading pathogens [1]. It specifically recognizes and binds to chemical patterns of sugars on the surfaces of various bacteria, viruses, and fungi [2]. Once bound, it activates the complement system, a cascade of proteins that destroys the invaders and alerts other immune cells [2]. Genetic variations in this gene are the primary cause of differences in circulating lectin levels among individuals [1].
Variant Impact: This variant, rs1800451, is a missense mutation in exon 1 of the MBL2 gene, resulting in an amino acid substitution from glycine to glutamate at position 57 [3]. This structural change, often referred to as the C variant or codon 57 mutation, disrupts the collagen-like backbone of the protein [3]. Because of this structural disruption, the protein cannot assemble properly into its active oligomeric forms [4]. Consequently, the defective proteins are rapidly degraded, leading to a significant reduction in functional mannose-binding lectin in the blood [4].
Key Insight: While low levels of this immune protein are traditionally linked to infection susceptibility in early childhood, evolutionary studies suggest the variant allele may actually provide protection against certain intracellular pathogens like tuberculosis.
Location: MBL2. Chromosome 10 · 10q21.1 · 52.8 Mb
Estimated prevalence by population
Global 86.3%; European 96.5%; African 60.1%; East Asian 100.0%; South Asian 93.5%; Americas 93.4%; Ashkenazi 94.2%; Finnish 98.6%; Middle Eastern 86.2%; Amish 98.5%.
Estimated CC genotype frequency.
Global 12.3%; European 3.5%; African 34.8%; East Asian 0.0%; South Asian 6.3%; Americas 6.5%; Ashkenazi 5.7%; Finnish 1.4%; Middle Eastern 13.3%; Amish 1.5%.
Estimated CT genotype frequency.
Global 1.4%; European < 0.1%; African 5.0%; East Asian 0.0%; South Asian 0.1%; Americas 0.1%; Ashkenazi 0.1%; Finnish < 0.1%; Middle Eastern 0.5%; Amish < 0.1%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Immunity & Inflammation
Inflammatory & Circulating Protein Markers
MBL Protein Levels. Evidence: 8/10. Source: PMID 29875488. Typical Levels.
Infection Susceptibility & Resistance
Tuberculosis. Evidence: 3/10. Source: PMID 22417159. Typical Risk.
Showing effects for C/T genotype
MBL Protein Levels. Evidence: 8/10. Source: PMID 29875488. Reduced Levels.
Tuberculosis. Evidence: 3/10. Source: PMID 22417159. Lower Risk.
Showing effects for T/T genotype
MBL Protein Levels. Evidence: 8/10. Source: PMID 29875488. Deficient Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Having two copies of the reference C allele means the body produces fully functional mannose-binding lectin proteins [1]. These proteins successfully assemble into their active structures, allowing the innate immune system to recognize and clear common pathogens efficiently [1]. Large-scale genomic studies confirm that this genotype maintains typical circulating levels of the protein in plasma [2]. While this ensures standard first-line defense against many everyday infections, it does not carry the specific evolutionary protection against certain intracellular bacteria seen with the variant allele [1].
Standard innate immune defense; Typical circulating MBL levels.
Sample genotype: CT (Heterozygous)
Carrying one copy of the structural variant allele results in a mixture of normal and altered proteins, which moderately reduces overall functional levels in the blood [1]. Although circulating levels are lower, clinical databases classify this carrier status as benign and of low clinical importance for overall health [2]. Interestingly, this moderate reduction in protein levels may alter how the immune system interacts with specific pathogens [1]. Some epidemiological studies suggest that carriers may have a lower susceptibility to certain chronic infections, such as pulmonary tuberculosis, compared to non-carriers [1].
Moderately lower MBL levels; Potential protection against tuberculosis.
Sample genotype: TT (Homozygous)
Having two copies of the variant allele severely limits the assembly of functional mannose-binding lectin, leading to highly reduced or deficient levels in circulation [1]. Despite this deficiency, clinical consensus and submitters in ClinVar classify this genotype as benign, meaning it is harmless on its own and does not cause clinical disease [2]. The body relies on many overlapping immune mechanisms to defend against pathogens, which compensates for the low levels [1]. Furthermore, this structural deficiency is associated with a reduced risk of contracting pulmonary tuberculosis, suggesting an evolutionary trade-off that preserved the variant in certain populations [1].
Highly reduced MBL levels; Lower risk of tuberculosis infection.
Variants with shared genetic architecture
rs5030737 · MBL2 Gene · Chr 10 · Immune and Heart Health
rs1800450 · MBL2 Gene · Chr 10 · Innate Immune Defense
rs7095891 · MBL2 Gene · Chr 10 · Immune System Function
The role of mannose-binding lectin in health and disease.
Mannose-binding lectin and its genetic variants.
Genomic atlas of the human plasma proteome.
DNA sequence variation and regulation of genes involved in pathogenesis of pulmonary tuberculosis.
Content updated August 2026.
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