Diagnosis of defects of antibody production.

Antibody function is a property of the immunoglobulins. Therefore antibody deficiency in its severest form implies immunoglobulin deficiency or agammaglobulinaemia. Since most patients with antibody deficiency produce at least some immunoglobulin, the term hypogammaglobulinaemia is to be preferred to the more absolute agammaglobulinae.mia. Hypogammaglobulinaemia due to a failure of antibody synthesis may be congenital or acquired, primary or secondary. This failure of synthesis is usually associated with a lack of mature plasma cells and rather less commonly with a lack of B lymphocytes. Immunoglobulin deficiency may affect all classes but often may be restricted to only one or two classes or subclasses. Rare individuals show a functional antibody deficiency despite quantitatively normal amounts of all immunoglobulin classes. The spectrum of primary antibody deficiency syndromes is shown in Table 1. Secondary antibody deficiency due to immunoglobulin loss usually affects mainly IgG and is associated with a degree of hypoproteinaemia and hypoalbuminaemia.