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. Analyze a fresh sample or store 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 recommended in cases of suspected deficiency.
2. In case of repeated infections of the sinuses, respiratory system, and GIT.

What factors will influence the result of immunoglobulin A(IgA)?

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. It is present mainly in the serum.
   2. IgA2. It is present in the secretions.
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. IgA is 15%  to 20% of the total immunoglobulins (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. Light chain of IgA:
   1. It has paired kappa (κ) or lambda (λ) chains.
7. Heavy chain of IgA:
   1. 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-lymphocytes.
11. The presence of IgA in secretion:
    1. IgA antibodies are found in the digestive system, respiratory system, colostrum, milk, nose, eyes,  and vagina.
    2. 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 region between the β and γ regions.
    2. IgA migrates in the pregamma region and a portion in the γ region.
    3. IgM is also present in the pregama and γ-region.
13. The average adult level is attained by age 16.
14. IgA concentration is >1mg/dL, and CSF contains 0.1 to 0.6 mg/dL.

What is the normal structure of IgA?

1. IgA consists of a dimer structure.
2. There is a J chain that joins the two immunoglobulin molecules.
3. Also, there is 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 via the alternative pathway.
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.
5. IgA secretory components are very important in protecting the mucous membrane.
   1. Its importance in secretion is to protect from microorganisms like tears, saliva, nasal fluids, and colostrum.
6. IgA deficiency leads to:
   1. Infections of the gastrointestinal system.
   2. Infection of the respiratory system.
   3. Allergy.
   4. Autoimmune disease.
7. Defensive role of IgA:
   1. It has antiviral activity.
   2. It blocks bacterial adherence.
   3. It protects the mucosal lining.
8. Its major role is to protect against bacterial, viral, and protozoal infections by preventing their attachment and colonization of the mucosa.
9. There is mucosal immunity and protection of:
   1. Gastrointestinal tract.
   2. Respiratory system.
   3. Tears.
   4. Saliva.
   5. Breast milk.

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 associated with increased Immunoglobulin A (IgA) levels?

1. Multiple Myeloma
2. Cirrhosis of the 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)

Questions and answers: