Immunoglobulin A (IgA)

What sample is needed for Immunoglobulin A (IgA)?

1. The patient’s serum is needed to estimate IgA.
2. A random sample can be taken.
3. Analyzed a fresh sample or stored it at 4 °C for less than 72 hours. Stable for 6 months at -20 °C.
4. Avoid lipemic or hemolyzed serum.

What are the indications for Immunoglobulin A (IgA)?

1. IgA level is advised in the case of suspected deficiency.
2. In case of repeated infections of the sinuses, respiratory system, and GIT.

What factors will influence the result?

1. Drugs that will increase the values are:
   1. Hydralazine.
   2. Phenytoin.
   3. Isoniazid (INH).
   4. Procainamide.
   5. Tetanus toxin and toxoid.
   6. Therapeutic gamma globulins.

How will you discuss the pathophysiology of Immunoglobulin A (IgA)?

1. IgA is the second most common Ig, and it has two subclasses:
   1. IgA 1
   2. IgA2
2. It has two categories:
   1. Secretory IgA.
   2. Monomer IgA.
      1. IgA monomer is present in high concentrations in human serum (90 to 450 mg/dL or 55 to 270 IU/L).
3. It is 15%  to 20% of the total Ig.
4. IgA is the predominant immunoglobulin in the secretion of tears, saliva, colostrum, milk, and intestinal secretions.
5. It has a half-life of 6 days.
6. It has paired kappa (κ) or lambda (λ) chains,
7. Two heavy chains.
8. IgA consists of two monomers joined by J-chain and secretory fragments.
   1. IgA monomer form is found in high concentrations in the serum (90 to 450 mg/dL in a normal adult).
9. IgA antibodies are produced by the plasma cells.
10. The plasma cells are derived from activated B-B-lymphocytes.
11. The presence of IgA secretion is present In:
    1. IgA antibodies are found in the digestive system, respiratory system, colostrum, milk, nose, eyes,  and vagina.
       1. IgA is also found in saliva, tears, and blood.
12. Immunoglobulins are present in the γ and β-region on the electrophoresis.
    1. IgG migrates in the area between the β-region and γ-region.
    2. IgA migrates in the pregamma region and some portion in the γ-region.
    3. IgM is also present in the pregama and γ-region.
13. The average adult level is attained by the age of 16 years.
    1. IgA concentration is > 1mg/dL, and CSF contains 0.1 to 0.6 mg/dL.

Immunoglobulin A (IgA): Immunoglobulins electrophoresis pattern

What is the normal structure of IgA?

1. IgA consists of a dimer structure.
2. There is a J-chain that joins the two molecules of immunoglobulins.
3. Also, there is a secretory piece.

Immunoglobulin A (IgA): IgA structure

Immunoglobulin A (IgA): IgA structure with a secretory piece

What are the Functions of Immunoglobulin A (IgA)?

1. IgA antibodies’ main function is to protect the mucosa exposed to various antigens.
2. It can activate complement by alternative pathways.
3. It is an effective opsonin.
4. The secretory IgA consists of two 4- 4-basic chain units (dimeric form) joined by the J-chain.
   1. IgA secretory components are very important in protecting the mucous membrane.
   2. Its importance in secretion is to protect from the microorganisms like tears, saliva, nasal fluids, and colostrum.
5. The deficiency of IgA leads to infection of the gastrointestinal and respiratory systems.
6. It has antiviral activity.
7. Its major role is protecting against bacteria, viruses, and protozoal infections by preventing their attachment and colonization of the mucosa.

What is the Normal level of Immunoglobulin A (IgA)?

Source 1

• To convert into SI unit x 10 = mg/L

Source 2

• Adult = 85 to 385 mg/dL
• Children = 1 to 350 mg/dL

Another source

• 0 to <5 months = 7.0  to  37.0 mg/dL
• 15 to <24 months =  36  to  79 mg/dL
• 2 to <4 years =  27 to  246 mg/dL
• 10 to <13 years =  42 to  295 mg/dL
• 16 to <18 years =  60 to 337 mg/dL
• more than 18 years = 61 to  356 mg/dL

What are the conditions with increased Immunoglobulin A (IgA) levels?

1. Multiple Myeloma
2. Cirrhosis of liver
3. Systemic lupus erythematosus
4. Rheumatoid arthritis
5. Sarcoidosis
6. Wiskott-Aldrich syndrome

What are the conditions with decreased levels of Immunoglobulin A (IgA)?

1. Hereditary telangiectasia
2. Type 111 dysgammaglobulinemia
3. Malabsorption in some cases
4. Occasional cases of Cirrhosis of the liver.
5. Occasional cases of SLE
6. Occasional cases of Still’s disease
7. Occasional cases of recurrent otitis media
8. In Agammaglobulinemia
9. Hereditary thymic aplasia
10. Waldenstrom macroglobulinemia
11. Non-IgA myeloma
12. Acquired immune deficiency syndrome (AIDS)