Antibodies Flashcards
What are antibodies?
Glycoproteins that are provoked by antigens
List two functions of antibodies.
Antigen recognition, and recruitment of other immune cells and molecules
Antibodies are found in serum and __________ ________.
Interstitial fluid
Antibodies prevent virus and bacteria entry through ____________.
Neutralisation
_______________ facilitate destruction of pathogens via opsonisation, and induce development of inflammation.
Antibodies
What is neutralisation?
Antibodies block antigenic activity of many pathways
What is opsonisation?
Antibody coats microbe, and targets it for phagocytosis
What is agglutination?
Antibody induces microbe clumping
What is complement activation?
Antibody:antigen complexes activate the complement proteins (of the classical pathway), resulting in lysis
All IgG antibodies have four chains (two light, weighing 23kD, and two heavy, weighing 50-70kD, chains), linked by ___________ bonds.
Disulphide
____________ regions have amino acids from 1 to 113.
Variable
Constant regions have amino acids from 111 to ____.
214
Antigen binds to the variable region, while the constant region is involved in _________ _________.
Effector function
True or false: variable regions differ from antibody to antibody.
True
True or false: an IgG antibody has three identical antigen binding sites.
False
Hypervariable regions (HR) form most of the _________ ___________ for the binding of the antibody to the antigen.
Contact residues
What other term is used to refer to hypervariable regions?
Complementary determining region
_____ is Y-shaped, composed of three 50 kD fragments after pepsin digestion.
IgG
Two ______ fragments bind antigen, and one F’c fragment is involved in effector function.
F’ab
F’ab and F’c ________ are flexible, and can adopt numerous orientations, to suit binding.
Regions
Describe IgG antibodies.
Most common Ig in serum. Consist of two y heavy chains and two k or i light chains, with two binding sites. Four subclasses of IgG exist (IgG1, IgG2, IgG3, and IgG4 (differ in amino acids)). IgG1, 2, and 3 can cross the placenta. IgG3 is the most effective for complement activation. IgG1 and IgG3 bind with high affinity to receptors on phagocytes, and are best for opsonisation
Which antibody class does the below passage describe?
Represents 5-10% of serum Ig. Exists as a pentamer, with five monomeric units, joined by disulphide bonds, with ten antigen binding sites. It is the first Ig produced in a primary response to antigen, binds more efficiently than other Igs to viruses, and is proficient at neutralising.
IgM
Describe IgA antibodies.
10-15% of serum Igs. Most commonly-secreted Ig in breast milk, saliva, tears, and mucus, and exist as a dimer of two monomers linked by a joining (J)-chain. Bind bacteria and viruses, preventing their attachment. They help to prevent newborn infections in the first months of life. They have four binding sites
Which antibody class does the following description outline?
Exists only as a monomer, and found in low levels in serum. Its role in serum is uncertain, and it does not bind complement, or cross placenta. It is not known for opsonisation and neutralisation abilities, and has two identical binding sites, with Δ heavy chains.
IgD
