Which components of the immune system are involved in the PID syndromes?
All components (B cell, T cell/natural killer [NK] cell, phagocytes, complement system) of the immune system have been shown to be affected in various PID syndromes. Humoral (antibody) immunodeficiencies constitute the majority of PIDs. Many humoral (B cell) immunodeficiencies occur in combination with T-cell deficiencies due to the dependence of antibody development on normal T-cell function as well as shared genes involved in both T-cell and B-cell development. Some of the more recently recognized disorders involve mutations in components of the innate immune system, mutations that involve genes that control fundamental cellular development (DOCK8) or metabolic functions. The individual PID syndromes may be due to dysfunction of a single component of the immune system, such as C4 deficiency, or dysfunction of multiple components, such as impairment of B-cell, T-cell, and phagocyte function in certain severe combined immunodeficiencies (SCIDs).