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RFX5 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

RFX5 gene

The RFX5 gene is critical for the production of MHC class II proteins, which are essential for the immune system to recognize and fight foreign invaders.

Normal Function

The RFX5 gene provides instructions for making a protein that helps control the activity (transcription) of major histocompatibility complex (MHC) class II genes. The RFX5 protein is part of the regulatory factor X (RFX) complex, which attaches to specific regions of DNA to turn on the production of MHC class II proteins.

MHC class II proteins are found on the surface of immune cells, such as white blood cells (lymphocytes). They play a vital role in the immune response by binding to fragments of proteins (peptides) from foreign invaders like bacteria, viruses, and fungi. This allows other immune cells to recognize the threat and launch an immune response. The RFX complex also plays a role in the transcription of MHC class I genes, though it is not the primary regulator for those genes.

Health Conditions Related to Genetic Changes

Bare lymphocyte syndrome type II

At least seven mutations in the RFX5 gene have been found to cause bare lymphocyte syndrome type II (BLS II). This is a type of combined immunodeficiency (CID) where individuals have virtually no immune protection from foreign invaders.

  • Effect of Mutations: Mutations lead to an abnormally short, nonfunctional RFX5 protein.
  • Impact on Immunity: The RFX complex cannot bind to DNA, preventing the transcription of MHC class II proteins.
  • Clinical Result: Because lymphocytes lack MHC class II proteins on their surface, the body cannot effectively identify or eliminate bacteria, viruses, and fungi, leading to life-threatening, persistent infections.

Frequently Asked Questions

RFX5 mutations are inherited in an autosomal recessive manner. Both parents are typically carriers, each contributing one defective allele. Genetic carrier testing can be offered to siblings and extended family members, and prenatal or preimplantation genetic diagnosis is available for future pregnancies.===
Confirmation typically involves a combination of flow cytometry to detect absent or markedly reduced MHC class II expression on lymphocytes, followed by targeted sequencing of the RFX5 gene to identify pathogenic variants. In some cases, whole-exome sequencing may be used if the clinical picture is atypical.
Children with RFX5 mutations often present with severe, persistent respiratory infections, chronic diarrhea, and failure to thrive before the age of two. They may also have recurrent fungal infections and a history of sepsis that does not resolve with standard antibiotic therapy. If these symptoms occur together, especially in a family with a history of immunodeficiency, a clinician should consider RFX5 testing.
Management centers on preventing and promptly treating infections: lifelong prophylactic antibiotics, regular intravenous immunoglobulin (IVIG) infusions to provide passive immunity, and aggressive treatment of any breakthrough infections. For eligible patients, hematopoietic stem cell transplantation (HSCT) offers the only curative option, but it carries significant risks and requires a matched donor.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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