How does the gene change cause symptoms in X-linked agammaglobulinemia?
The BTK gene produces a protein called Bruton tyrosine kinase. Because of a change in the gene, people with X-linked agammaglobulinemia do not produce enough of this protein. This protein is important in the process to create B cells, which are a type of white blood cell. B cells are part of the immune system; they can mature into plasma cells. Plasma cells produce antibodies. When Bruton tyrosine kinase is absent or not working properly, antibodies are not produced. Antibodies are specialized proteins that help to protect the body from germs and microorganisms like bacteria and viruses. Without enough antibodies, the immune system cannot protect the body from these harmful materials. People with X-linked agammaglobulinemia are highly susceptible to developing infections.
X-linked Agammaglobulinemia. Genetic Home Reference website. https://ghr.nlm.nih.gov/condition/x-linked-agammaglobulinemia Accessed June 3, 2016.
Conley ME, Howard VC. X-linked Agammaglobulinemia. GeneReviews website. http://www.ncbi.nlm.nih.gov/books/NBK1453/ Accessed May 16, 2016.