Interleukin 28B (interferon-λ 3) is a protein that in humans is encoded by the IL28B gene. IL28B has recently been renamed IFNL3 as its official gene symbol.[1]
This gene encodes a cytokine distantly related to type I interferons and the IL-10 family. This gene, interleukin 28A (IL28A), and interleukin 29 (IL29) are three closely related cytokine genes that form a cytokine gene cluster on a chromosomal region mapped to 19q13. Expression of the cytokines encoded by the three genes can be induced by viral infection. All three cytokines have been shown to interact with a heterodimeric class II cytokine receptor that consists of interleukin 10 receptor, beta (IL10RB) and interleukin 28 receptor, alpha (IL28RA). [provided by RefSeq, Jul 2008].[1]
Implications to hepatitis C treatment
In individuals with chronic hepatitis C (HCV), the presence of specific polymorphisms (rs12979860) near the IL28B gene has been associated with an increased response in treatment for the condition with interferon and ribavirin. This polymorphisim was found to be associated with another nearby interferon called as IFNL4 and hence has a potential role in HCV clearance.[2][3] The same polymorphisms were also demonstrated at higher frequencies in individuals infected with hepatitis C who cleared the infection spontaneously, compared to those that developed chronic hepatitis from the condition.[4][5] A functional variant that determines the production of an antiviral protein has been linked to the polymorphisms in IL28B and implicated in the clearance of hepatitis C virus.[6]
A non-coding genetic polymorphism (rs4803217) has been shown to significantly change the RNA structure and translation of IFNL3. The dynamic structure of the non-coding RNA produced by the rs4803217 polymorphism may be responsible for the increased HCV clearance of this allele.[7]
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