CLINICAL RELEVANCE OF IGG SUBCLASS DEFICIENCIES

Patients with primary or secondary IgG subclass deficiencies suffer fr om infections due to encapsulated microorganisms such as H influenzae and pneumococci. In addition to relapsing infections, some patients wi th primary subclass deficiencies may have autoimmune disorders. The be st characterized defect is IgG2 deficiency, either isolated or combine d with IgC4 deficiency. It is frequently associated with IgA deficienc y or with ataxia teleangiectasia. IgG1 deficiency occurs mostly in com bination with disturbances of other immunoglobulin isotypes, and proba bly represents a form of common variable immune deficiency. Decreased IgG3 levels were reported in association with lung dysfunction and vir al diseases. Except in IgG1 deficiency, total IgG serum levels in prim ary as well as secondary IgG subclass deficiency states may be normal or even increased. It is assumed that IgG subclass deficiencies repres ent an indicator of more basic immunologic abnormalities. There is evi dence that antibody defects correlate better with the clinical symptom s than the total serum IgG subclass concentrations. In patients with s evere recurrent infections and IgG subclass deficiency, intravenous im munoglobulin treatment at dosages of 0.3 to 0.4 g/kg body weight every 3-4 weeks is indicated.