Back

IgG Subclasses

0 Azn
Add to basketAdded

Immunoglobulins (antibodies) are key components of the immune system, protecting the body from foreign invaders, bacteria, viruses, and toxins. There are five major immunoglobulin classes: IgG, IgA, IgM, IgE, and IgD.

What are IgG Subclasses?

  • IgG is the most abundant antibody class, making up 70-80% of total immunoglobulins in the blood.
  • It provides long-term immunity, neutralizes toxins and viruses, and activates phagocytosis and the complement system.
  • IgG is the only immunoglobulin that crosses the placenta, protecting newborns for 4-6 months.
  • IgG is divided into four subclasses:
    • IgG-1: The most abundant (~60-70%), responds to protein antigens (viruses, bacteria, vaccines).
    • IgG-2: Responds to polysaccharide antigens (bacterial capsules, pneumococcus, H. influenzae).
    • IgG-3: Important for viral infections and activating the complement system.
    • IgG-4: Plays a role in immune regulation and tolerance, associated with chronic inflammatory diseases and IgG4-related disease (IgG4-RD).

Clinical Significance

  • A total IgG test may appear normal, but subclass deficiencies can cause recurrent infections.
  • IgG subclass deficiency often affects other immunoglobulin classes, particularly IgA deficiency, which is linked to low IgG-2 and IgG-4 levels.
  • Take the test at least 2 hours after the last meal.
  • Avoid smoking for 3 hours before the test.
  • Avoid physical and emotional stress for 1 hour before the test.
  • Evaluation of humoral immunity
  • Diagnosis of immunodeficiency syndromes
  • Investigation of recurrent bacterial, viral, fungal, or parasitic infections in adults and children
  • Assessment of immune function in autoimmune diseases
  • Monitoring the effectiveness of immunoglobulin therapy

Elevated IgG Subclass Levels May Indicate:

  • Acute and chronic infections (respiratory, gastrointestinal, genitourinary)
  • Recovery phase after primary infection
  • Acute phase of secondary infections
  • Chronic liver diseases:
    • Autoimmune hepatitis
    • Viral hepatitis
    • Cirrhosis (including alcohol-induced liver damage)
  • IgG-type multiple myeloma (plasma cell cancer)
  • Cystic fibrosis
  • Waldenström’s macroglobulinemia
  • Chronic lymphocytic leukemia (CLL)
  • Lymphomas
  • Infectious mononucleosis
  • Neurosyphilis
  • HIV/AIDS

Reduced IgG Subclass Levels May Indicate:

  • Physiological hypogammaglobulinemia in infants (3-5 months old)
  • Common variable immunodeficiency (CVID)
  • Bruton’s agammaglobulinemia (X-linked immunodeficiency)
  • Hypogammaglobulinemia
  • Leukemia
  • Splenectomy (removal of the spleen)
  • Hyper-IgM syndrome
  • Vitamin B12 deficiency
  • Ataxia-telangiectasia (Louis-Bar syndrome)
  • Wiskott-Aldrich syndrome
  • Chronic inflammatory bowel disease (IBD, Crohn’s, ulcerative colitis)
  • Nephrotic syndrome