Iga

Immunoglobulin A is a group of human plasma proteins with antibody properties. IgA is mainly found in external body fluids (e.g. saliva, tear fluid, nasal mucus, milk, or intestinal secretions) where it performs an important defence function against pathogens. The determination of IgA is used for diagnosis and follow-up of antibody deficiency.

IgA occurs in 2 subclasses:

• IgA1

and

• IgA2

The ratio IgA1/IgA2=9:1;

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Normal values for immunoglobulin A.

Age IgA normal range

4 to 5 years 30 - 190 mg/dl

6 to 7 years 38 - 220 mg/dl

8 to 9 years 46 - 250 mg/dl

10 to 11 years 52 - 270 mg/dl

Adults 70 - 400 mg/dl

Standard value: The reference range for adults is between 70 and 400 mg/dl. IgA forms about 15 % of all immunoglobulins. 90% of IgA is present in monomeric form, 10% in polymeric form. Serum IgA tends to form complexes, especially with albumin, but also with enzymes to form macroenzymes.

IgA antibodies occur as serum IgA and as secretory IgA. As IgA cannot cross the placental barrier, it is not present in the fetal blood. It is produced slowly after birth. At the end of the 1st year of life, the infant has about 25% of the IgA of the awakened child, at the 16th year of life the values of the adult.

IgA pathologically decreased: B- and T-cell defects, combined immunodeficiencies, viral infections, exudative enteropathy, nephrotic syndrome, burns, malignant monoclonal gammopathies, lymphatic leukemias, Hodgkin's and non-Hodgkin's lymphomas, drugs

IgA pathologically elevated: malignant and benign monoclonal gammopathies, acute hepatitis, chronic persistent hepatitis, infections, rheumatic diseases, liver cirrhosis, primary biliary cirrhosis, infections.

Deposits of IgA complexes in tissue are found in dermatitis herpetiformis Duhring, IgA lineardermatosis, IgA nephropathy and Purpura Schönlein-Henoch .

Selective immunoglobulin A deficiency (IGAD) is the most common form of primary immunodeficiency (PID) with an incidence of approximately 1 in 600 individuals in the Western world (Cunningham-Rundles 2001). IgA deficiency can affect either of two subtypes IgA1/IgA2):

• Immunoglobulin A deficiency selective, type 2 mutation in TNFRSF13B.
• Immunoglobulin A deficiency type 1

Since IgA deficiency may be transient in rare cases, repeat measurement after 1-2 months is recommended. The overarching term "common variable immunodeficiency" (CVID) refers to a group of diseases characterized by deficiency of all Ig isotypes. Selective IgA deficiency and CVID can occur in the same family.