Medically Reviewed by: Dr. Dipak Ladda, M.D.
Expertise: Consultant Pathologist
Last Updated: July 22, 2026
Medical Analysis
Understanding Interleukin-28B (IL28B) Polymorphism: Genomic Insights and Clinical Significance
Interleukin-28B, commonly referred to as IL28B, is a significant genetic factor located on the long arm of chromosome 19 [1, 2]. This gene is responsible for encoding interferon λ3 (IFN λ3), which is classified as one of the type III interferons [5, 6]. Within the same family, IL29 and IL28A are responsible for encoding other type III interferons, specifically IFN λ1 and IFN λ2, respectively [9, 10]. The genetic polymorphism of IL28B has been identified as being significantly associated with the sustained virological response (SVR) rate in patients diagnosed with chronic hepatitis C who are undergoing treatment with pegylated interferon-α (PEG-IFN) combined with ribavirin [1, 2, 3]. Furthermore, this polymorphism plays a crucial role in spontaneous hepatitis C virus clearance [4].
The primary function of these proteins involves potent antiviral and immunomodulatory properties [9]. While these properties are similar to those observed in type I interferons, the cellular expression of type III interferons is notably more limited, providing a specialized response mechanism [9, 10]. Interleukin-28 exists in two specific isoforms, known as IL-28A and IL-28B [10]. This system serves a vital role in the body’s immune defense against various viral infections [9, 11]. Specifically, it facilitates the induction of an “antiviral state” by activating several key proteins, including Mx proteins, 2′,5′-oligoadenylate synthetase, and ISGF3G (Interferon Stimulated Gene Factor 3) [9, 10].
Genetic Significance and SNP Profiling in Hepatitis C
The genetic landscape of IL28B is defined by several key single nucleotide polymorphisms (SNPs), which include rs12979860, rs8099917, rs12980275, and rs72486680 [1, 2, 3]. Among these, the CC genotype at the rs12979860 locus is widely recognized for its association with a favorable response to hepatitis C antiviral therapy, specifically the regimen consisting of pegylated IFN-α and ribavirin [1, 2, 3]. It is important to note that the distribution of these favorable alleles exhibits significant variation based on ethnicity [11, 15]. Data indicates that these alleles are most frequently found in Asian populations, whereas they are observed least frequently in African-American populations [11]. Regarding its role in disease management, IL28B status serves as a predictive marker for sustained virological response (SVR), particularly in patients infected with hepatitis C virus (HCV) genotype 1 and genotype 4 [7, 8]. Conversely, its impact is observed to be less significant in patients with genotype 2 or 3 infections [7, 13].
Clinical Indications and Advanced Assay Methods
The primary clinical indication for testing IL28B remains the management of Hepatitis C [7, 14]. To assess the genetic status of a patient, laboratories utilize several advanced assay methods. These techniques include:
Polymerase Chain Reaction and Sequencing Technique: A standard molecular approach for genetic analysis [1, 3].
Real-time PCR with allelic discrimination: Often utilizing TaqMan or similar probe-based technologies for precision [15].
PCR-CTPP: This is a cost-effective multiplex PCR-mini assay used for rapid screening [15].
Protocols for Sample Collection, Processing, and Storage
Ensuring the accuracy of molecular testing requires strict adherence to sample collection protocols [13]. Blood samples must be collected in an EDTA tube (lavender capped), requiring a minimum of 6.0 ml, with 3.0 ml being taken in each tube [13, 14]. It is imperative to separate the plasma as early as possible after collection [14]. When processing samples for sensitive genetic analyses, the procedure follows a structured path including centrifugation and storage at -80°C [15]. Alternatively, saliva is an accepted sample type; the patient must not eat, drink, smoke, or chew gum for 30 minutes prior to collection using a specialized Saliva Swab Collection Kit [15].
Clinical Applications and Prognostic Utility
The clinical application of IL-28B testing has traditionally been used to aid in decision-making for hepatitis C therapies [7, 11]. While its utility has decreased in the current era due to the availability of highly effective direct-acting antivirals (DAAs), it still provides valuable prognostic information [12, 14]. Beyond viral response, some IL-28B variants have been linked to differences in liver fibrosis, steatosis, and inflammation, with the degree of these effects showing heterogeneity by HCV genotype [14, 15]. Ultimately, IL28B testing remains a tool to predict sustained virological response to interferon-based therapy and provided essential guidance for personalized therapy [7, 11].
For Non-Medicos: Understanding Your Genetic Health
Understanding your genetic makeup can be important, especially when dealing with viral infections like Hepatitis C [11]. The IL28B gene is a natural part of your DNA that helps your body fight off viruses [1, 4].
Why IL28B Testing Matters If you are diagnosed with Hepatitis C, your doctor might look at your IL28B status [7].
Treatment Success: Certain genetic versions of this gene (called the CC genotype) are linked to a much better chance of clearing the virus with older interferon-based treatments [1, 2, 3].
Personalized Care: Even though newer medicines (DAAs) are now very effective, knowing your genetic status can still provide your medical team with useful information about your liver health [12, 14].
Beyond the Virus: Your IL28B status can sometimes influence how your liver reacts to inflammation or scarring (fibrosis), helping your doctor understand your overall liver health [14, 15].
How Testing Works Testing usually requires a small blood sample collected in a special purple-topped tube (EDTA) or a simple saliva swab [13, 15]. Just remember not to eat, drink, or smoke for 30 minutes before providing a saliva sample [15]. By understanding these simple facts, you can take a more active role in your health journey, working alongside your doctor to manage your condition effectively [11, 14].
References:
Ge, D., et al. (2009). Genetic variation in IL28B predicts hepatitis C treatment-induced viral clearance. Nature.
Suppiah, V., et al. (2009). IL28B is associated with response to chronic hepatitis C interferon-alpha and ribavirin therapy. Nature Genetics.
Tanaka, Y., et al. (2009). Genome-wide association of IL28B with response to pegylated interferon–alpha and ribavirin therapy for chronic hepatitis C. Nature Genetics.
Thomas, D. L., et al. (2009). Genetic variation in IL28B and spontaneous clearance of hepatitis C virus. Nature.
O’Brien, T. R., et al. (2014). IFN-λ4: the paradoxical new member of the interferon lambda family. Journal of Interferon & Cytokine Research.
Prokunina-Olsson, L., et al. (2013). A variant upstream of IFNL3 (IL28B) creating a new interferon gene IFNL4 is associated with impaired clearance of hepatitis C virus. Nature Genetics.
Thompson, A. J., et al. (2010). IL28B polymorphism: genotype-guided therapy for hepatitis C. Journal of Hepatology.
Feld, J. J., & Hoofnagle, J. H. (2011). The role of IL28B in the management of hepatitis C. Gastroenterology.
Pagliaccetti, N. E., & Robek, M. D. (2010). Antiviral therapeutics: the role of interferon-lambda. Antiviral Research.
Wozniak, M. A., & Robek, M. D. (2010). Recent advances in the understanding of the interferon-lambda family. Future Virology.
Kilaru, S., & Gish, R. (2010). IL28B: the impact of genetics on hepatitis C treatment. Current Hepatitis Reports.
Tillmann, H. L. (2014). Antiviral therapy for hepatitis C: where are we now?. World Journal of Gastroenterology.
European Association for the Study of the Liver. (2014). EASL Clinical Practice Guidelines: Management of hepatitis C virus infection. Journal of Hepatology.
Mangia, A., & Thompson, A. J. (2017). IL28B and HCV: from host genetics to clinical practice. Liver International.
Chen, J., et al. (2016). Genetic polymorphisms of IL28B and the response to therapy in patients with chronic hepatitis C: A meta-analysis. Medicine.
FAQ’s:
What is IL28B?
It is a genetic factor on chromosome 19 that encodes a type III interferon protein.What does IL28B do?
It provides antiviral and immunomodulatory defense, helping the body fight off various viral infections.Why is IL28B significant?
It predicts how well patients with chronic Hepatitis C respond to specific interferon-based antiviral treatments.Which genotype is favorable?
The CC genotype at the rs12979860 locus is associated with favorable responses to antiviral therapy.How is IL28B tested?
Labs use techniques like real-time PCR or sequencing to identify specific genetic variants in patients.Are saliva tests used?
Yes, saliva swabs are accepted if the patient avoids eating or smoking for 30 minutes before.How is blood stored?
Plasma must be separated quickly and stored at -80°C for accurate genetic analysis results.Is it used for Hepatitis?
Yes, it is used for Hepatitis C management to help predict patient responses to older therapies.Does ethnicity affect results?
Yes, the frequency of favorable IL28B alleles varies significantly between different ethnic populations.Does it predict liver health?
Yes, certain IL28B variants are linked to differences in liver inflammation, fibrosis, and steatosis.
