Antibodies. Properties and functions of the

immunoglobulins

Vinnitsa National Pirogov Memorial Medical University / Department of microbiology

Antibody

Antibodies or immunoglobulins (Ig) are a group of glycoproteins present in the blood serum and tissue serum

Functions of immunoglobulins1. Complement activation

2. Opsonization

3. Prevention of microorganism attachment

4. Neutralization toxins and viruses

5. Restriction of microorganism mobility

6. Agglutination of bacteria

Immunoglobulin structure

Classes of immunoglobulins

Ig G γ (gamma) Ig A α (alpha) Ig M μ (mu) H-chain Ig D δ (delta) Ig E ε (epsilon)

L chains : κ (kappa) or λ (lambda)

Structure of the immunoglobulin monomer molecule

Immunoglobulin antigen determinants Isotypic markers Allotypic markers Idiotypic markers

Immunoglobulin classes Ig G. It has molecular weight 160 000 D The normal serum concentration of Ig G

is 8-16 mg/ml.

Ig A It constitutes 10-15% of

total serum globulin Normal serum level is

0,6-4,2 mg/l It has molecular weight

170 000 D

Differences between serum and secretory Ig A

Ig M It constitutes 5-10% serum globulin or 0,5-2

mg/ml It has half-life of 5-10 days and molecular weight

900 000 D

Ig D its concentration in average is 0,02-0,2

mg/ml) It has half-life of 3 days and molecular weight

160 000 D

Ig E It makes up only 0,0002-

0,002% of the total immunoglobulin pool

It has half-life of 2 days and molecular weight 190 000 D

The types of antibody response to antigen stimulation

Immune antibody response consists of 3 steps:

1. Entry and distribution of Ag in tissue and its contact with immunological competent cells

2. Processing of Ag and control of Ab forming process

3. Secretion of Ab, its distribution in tissue, body fluid and manifestation of its effect

Primary immune response It is slow Specific IgM can be detected in the serum from

the 4th day, titer rises to 7-12 days Specific IgG can be detected in the

serum from the 7th day and titer rises to 10-14th days

Secondary antibody response shorter lag phase IgM and IgG are synthesized in the same time It is provided by IgG

The types of the antibody immune response

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