It is an inherited defect of immunity, including lack of immunoglobulin synthesis, absence of cell-mediated immunity, thymic hypoplasia and a marked reduction in the number of thymic, splenic and blood lymphocytes. It is inherited as an autosomal recessive trait.
Various genetic defects are responsible for combined immune deficiency. Patients with CID disorder lack both B and T-cells, but have functional phagocytes. Defects in interaction of cell and cell signaling ensues immune deficiency.
A survey of 108 infants with CID suggests that the impaired cell signaling function of common gama chains of the 1L – 2 receptors was the most prevalent defect.
The next most common defect found in the infants was in the gene for the enzyme adenosine delaminate (ADA). Activity of ADA is high in lymphocytes, deficiency in adenosine delaminate results in accumulation of metabolic byproducts that are toxic to the cells.
In the some way, deficiency of urine nucleoside phospharylase (PNP) also cause combined immune deficiency. Defects in ZAP-70, an important element in T-cell signal transduction causes depletion of CD8 cells. There are several other genetically defects responsible for combined immune deficiency. Combined immune deficiency syndrome (disease).