TNF receptor superfamily member 13B: The TNFRSF13B gene provides instructions for making a protein called TACI.
The TNFRSF13B gene provides instructions for making a protein called TACI. The TACI protein is found on the surface of immune system cells called B cells. These specialized white blood cells help protect the body against infection from foreign invaders such as bacteria and viruses. When B cells mature, they produce special proteins called antibodies (also known as immunoglobulins). Antibodies attach to specific foreign invaders, marking them for destruction. Through interactions with other proteins, TACI promotes cell signaling, plays a role in B cell survival and maturation, and is involved in the production of antibodies.
More than 25 mutations in the TNFRSF13B gene have been associated with common variable immune deficiency (CVID). This condition impairs the immune system, resulting in increased risk for recurrent infections; autoimmune disorders, which occur when the immune system malfunctions and attacks the body's tissues and organs; and certain cancers.
Most of the TNFRSF13B gene mutations associated with CVID change single protein building blocks (amino acids) in the TACI protein. The most common mutation seen in people with CVID replaces the amino acid cysteine with the amino acid arginine at position 104 in the TACI protein (written as Cys104Arg or C104R). This mutation impairs the ability of TACI to interact with other proteins, disrupting cell signaling and preventing normal B cell maturation and antibody production. A shortage (deficiency) of certain antibodies makes it difficult for people to fight off infections. Abnormal and deficient immune responses over time likely contribute to the increased cancer risk in people with CVID.
Some people with TNFRSF13B gene mutations do not develop the signs and symptoms of CVID. In these individuals, additional genetic or environmental factors are probably needed for the condition to occur.