Genetically determined deficiencies in IgA and IgG.

Disturbance in the immune response can be caused by malfunction of T and/or B cells. Certain inborn errors such as absence of enzymes in the purine salvage pathway, may lead to severe combined immunodeficiencies or to other syndromes related to impaired immune response, that are mostly diseases of infancy. Selective immunodeficiencies in one or more immunoglobulin subclasses are less severe and occur among adults. The best known is IgA deficiency. The first case of IgG3 subclass deficiency was described in 1976 [13]. Examples of IgG1 and IgG2 deficiencies are reported in this paper. The implication of structural and of regulator genes in the various defects is discussed.