Table 2.

Predominantly antibody deficiencies

Associated designation	Serum Ig	Circulating B cells	Presumed pathogenesis	Inheritance	Associated features
1. X-linked agammaglobulinaemia	All isotypes decreased	Profoundly decreased	Mutations in btk	XL	Severe bacterial infections
2. Autosomal recessive agammaglobulinaemia	All isotypes decreased	Profoundly decreased	Mutations in μ Igα, Igβ, λ5, Vpreβ genes; or BLNK and syk genes	AR	Severe bacterial infections
3. Ig heavy-chain gene deletions	IgG1 or IgG2, IgG4 absent and in some cases IgE and IgA1 or IgA2 absent	Normal or decreased	Chromosomal deletion at 14q32	AR	Not always symptomatic
4. κ Chain deficiency mutations at AR	Ig(K) decreased: antibody response normal or decreased	Normal or decreased κ-bearing cells	Point mutations at chromosome 2p11 in some patients	AR	–
5. Selective Ig deficiency					Not always symptomatic
(a) IgG subclass deficiency	Decrease in one or more IgG isotypes	Normal or immature	Defects of isotype differentiation	Unknown
(b) IgA deficiency	Decrease in IgA1 and IgA2	Normal or decreased sIgA+	Failure of terminal differentiation in IgA+ve B cells	Variable	Autoimmune or allergic disorders; some have infections
6. Antibody deficiency with normal or elevated Igs	Normal	Normal	Unknown	Unknown	Selective inability to make antibody to polysaccharides
7. Common variable immunodeficiency	Decrease in IgG and usually IgA, ± IgM	Normal or decreased	Variable; undetermined	Variable	See belowa
8. Transient hypogamma-globulinaemia of infancy	IgG and IgA decreased	Normal	Differentiation defect: delayed maturation of helper function	Unknown	Frequent in families with other Ids
9. AID deficiency	IgG and IgA decreased	Normal	Mutation in activation-induced cytidine deaminase gene	AR	Enlarged lymph nodes and germinal centres

New defect: A deficiency of activation induced cytidine deaminse (AID) presents as a form of the hyper-IgM syndrome but differs from CD40L and CD40 deficiencies in that the patients have large lymph nodes with germinal centres and are not susceptible to opportunistic infections.

^aCommon variable immunodeficiency: there are several different clinical phenotypes, probably representing distinguishable diseases with differing immunopathogeneses.

Abbreviations: As for Table 1; Ig(K), immunoglobulin of kappa light-chain type; btk, Bruton's tyrosine kinase gene.