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Immunoglobulin A in the blood

Medical expert of the article

Prof. Eli SOMEH

Pediatric immunologist

Alexey Kryvenko, medical expert
Last reviewed: 05.07.2025

Immunoglobulin A includes two types of specific proteins: serum and secretory. Immunoglobulin A in the blood serum is in the form of a monomer (90% IgA ₁ ), is part of the β-globulin fraction and makes up to 15% of the Ig of the blood serum. Secretory IgA is contained in secretions (milk, saliva, tear fluid, secretions of the intestinal and respiratory tract) and exists only in the form of a dimer (IgA ₁ and IgA ₂ ). Antibodies of the immunoglobulin A class are synthesized mainly by lymphocytes of the mucous membranes in response to local exposure to antigens, protect the mucous membranes from pathogenic microorganisms, potential allergens and autoantigens. By binding to microorganisms, IgA AT inhibit their adhesion to the surface of epithelial cells and prevent penetration into the internal environment of the body, thereby preventing the development of local inflammatory processes. Local synthesis of immunoglobulin A determines local immunity. By penetrating into the internal environment of the body, Immunoglobulin A inactivates bacteria and viruses, activates complement via an alternative pathway. The half-life of immunoglobulin A is 6-7 days.

In humans, serum immunoglobulin A constitutes less than 50% of the total pool of this Ig.

Reference values for serum immunoglobulin A levels

Age	Concentration, g/l
Children:
1-3 months	0.06-0.58
4-6 months	0.1-0.96
7-12 months	0.36-1.65
2-3 years	0.45-1.35
4-5 years	0.52-2.2
6-7 years	0.65-2.4
10-11 years	0.91-2.55
12-13 years old	1.08-3.25
Adults	0.9-4.5

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