What you carry at this position in your DNA and what research says about it.
Hepatitis B and Eye Health: 6/10 evidence, 16 publications.
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Sample genotype (not yours): C/C
Higher Hepatitis B and Macular Degeneration Risk
This genotype is associated with a higher susceptibility to chronic hepatitis B infection and typical risk of age-related macular degeneration.
What this genotype means: Increased susceptibility to chronic hepatitis B; Typical risk of age-related macular degeneration; Better potential response to interferon antiviral therapy.
Sample genotype (not yours): C/T
Lower Hepatitis B and Macular Degeneration Risk
Carrying one copy of the T allele provides moderate protection against both chronic hepatitis B and age-related macular degeneration.
What this genotype means: Reduced risk of chronic hepatitis B; Lower risk of age-related macular degeneration; Slightly reduced response to interferon therapy if infected.
Sample genotype (not yours): T/T
Strong Protection Against Hepatitis B and Macular Degeneration
Two copies of the T allele offer the strongest protection against chronic hepatitis B and age-related macular degeneration, with minor trade-offs.
What this genotype means: Lowest risk of chronic hepatitis B; Lowest risk of age-related macular degeneration; Lowest response rate to interferon antiviral therapy if infected.
Gene function and biological role
Gene Function: The CFB gene encodes complement factor B, a crucial component of the alternative pathway of the complement system [1]. This system is a key part of the innate immune response, helping the body recognize and destroy invading pathogens like viruses and bacteria [2]. However, overactivation of this pathway can lead to chronic inflammation and tissue damage [1]. Consequently, genetic variations in CFB are frequently linked to inflammatory diseases, autoimmune conditions, and susceptibility to infectious diseases [3].
Variant Impact: The rs12614 variant is a missense mutation in the CFB gene that changes the amino acid at position 32 from arginine to tryptophan, often designated as the 32W variant [1]. This structural change alters how complement factor B binds to other immune proteins, resulting in less efficient activation of the alternative complement pathway [4]. While a dampened immune response can make it harder to clear certain infections, it also reduces the chronic, low-grade inflammation that drives tissue damage in the eyes [1]. This single molecular shift therefore creates a complex trade-off between infection susceptibility and inflammatory disease protection [4].
Key Insight: The same genetic variant that protects your eyes from age-related macular degeneration by dampening inflammation also significantly reduces your risk of developing chronic hepatitis B.
Location: CFB. Chromosome 6 · 6p21.33 · 31.9 Mb
Estimated prevalence by population
Global 69.8%; European 82.4%; African 45.0%; East Asian 88.1%; South Asian 65.6%; Americas 73.1%; Ashkenazi 82.9%; Finnish 69.3%; Middle Eastern 66.1%; Amish 82.8%.
Estimated CC genotype frequency.
Global 26.2%; European 16.8%; African 44.2%; East Asian 11.5%; South Asian 30.8%; Americas 24.8%; Ashkenazi 16.3%; Finnish 27.9%; Middle Eastern 30.4%; Amish 16.4%.
Estimated CT genotype frequency.
Global 3.9%; European 0.9%; African 10.8%; East Asian 0.4%; South Asian 3.6%; Americas 2.1%; Ashkenazi 0.8%; Finnish 2.8%; Middle Eastern 3.5%; Amish 0.8%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Immunity & Inflammation
Infection Susceptibility & Resistance
Hepatitis B. Evidence: 6/10. Source: PMID 25802187. ~1.9x Higher Risk.
Inflammatory & Circulating Protein Markers
Interferon Response. Evidence: 6/10. Typical Response.
Organ Systems
Vision & Eye Health
Macular Degeneration. Evidence: 3/10. Source: PMID 21541267. Typical Risk.
Cardiovascular & Metabolic
Lipids & Cholesterol
Total Cholesterol. Evidence: 7/10. Source: PMID 34887591. Typical Levels.
Showing effects for C/T genotype
Hepatitis B. Evidence: 6/10. Source: PMID 25802187. Reduced Risk.
Interferon Response. Evidence: 6/10. Lower Response.
Macular Degeneration. Evidence: 3/10. Source: PMID 21541267. Reduced Risk.
Total Cholesterol. Evidence: 7/10. Source: PMID 34887591. Slightly Higher.
Showing effects for T/T genotype
Hepatitis B. Evidence: 6/10. Source: PMID 25802187. Lowest Risk.
Interferon Response. Evidence: 6/10. Lowest Response.
Macular Degeneration. Evidence: 3/10. Source: PMID 21541267. Lowest Risk.
Total Cholesterol. Evidence: 7/10. Source: PMID 34887591. Higher Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Carrying two copies of the common C allele means complement factor B is fully active, which promotes standard inflammatory responses [1]. While this active immune state is generally efficient, it is paradoxically associated with a nearly twofold increased risk of developing chronic hepatitis B if exposed to the virus [2]. Additionally, the fully active complement system contributes to the chronic inflammation that drives age-related macular degeneration [1]. On the positive side, if a chronic hepatitis B infection does occur, individuals with this genotype tend to respond significantly better to pegylated interferon-alpha therapy compared to T allele carriers.
Increased susceptibility to chronic hepatitis B; Typical risk of age-related macular degeneration; Better potential response to interferon antiviral therapy.
Sample genotype: CT (Heterozygous)
Having one copy of the protective T allele reduces the overall activation efficiency of the alternative complement pathway [1]. This slight reduction in complement activity is highly beneficial, lowering the risk of developing chronic hepatitis B [2] and offering protection against age-related macular degeneration [1]. However, this altered immune profile means that if a chronic hepatitis B infection is established, the response rate to pegylated interferon-alpha therapy is lower than in those with the C/C genotype. There is also a minor association with slightly higher total and non-HDL cholesterol levels [3].
Reduced risk of chronic hepatitis B; Lower risk of age-related macular degeneration; Slightly reduced response to interferon therapy if infected.
Sample genotype: TT (Homozygous)
Carrying two copies of the T allele results in complement factor B proteins that activate the alternative complement pathway with much lower efficiency [1]. This significantly dampens chronic inflammatory processes, providing the highest level of genetic protection against age-related macular degeneration [1] and chronic hepatitis B infection [2]. The primary trade-off is that if a hepatitis B infection does become established, the likelihood of responding successfully to pegylated interferon-alpha antiviral therapy is at its lowest. Additionally, this genotype is linked to slightly elevated total and non-HDL cholesterol levels [3].
Lowest risk of chronic hepatitis B; Lowest risk of age-related macular degeneration; Lowest response rate to interferon antiviral therapy if infected.
Variants with shared genetic architecture
rs4151667 · CFB Gene · Chr 6 · Macular Degeneration Risk
rs641153 · CFB Gene · Chr 6 · Macular Degeneration Protection
rs1048709 · CFB Gene · Chr 6 · Eye Inflammation Risk
Complement factor B polymorphism 32W protects against age-related macular degeneration.
Complement alternative pathway genetic variation and Dengue infection in the Thai population.
Genetic variants in five novel loci including CFB and CD40 predispose to chronic hepatitis B.
The power of genetic diversity in genome-wide association studies of lipids.
Content updated August 2026.
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