1. The Antibody

2. The Antibody-Mediated Immune Response
Antigen activates naïve B cells and dendritic cells
Naïve T cell binds to APC and differentiates into effector and memory helper T cells
Helper T cells bind antigen-MHC complexes on activated B cell and secrete cytokines
B cell differentiates into effector B cells, which produce antibodies targeting a specific antigen, and memory B cells

3. Antibodies Immunoglobulins (Glycoproteins)
The heavy and light chains are polypeptides
The chains are held together by disulphide bridges
Each ab has 2 identical ag binding sites – variable regions.
The order of amino acids in the variable region determines the shape of the binding site

5. Antibodies and Other Antigen Receptors
Antigen receptors on B and T cells have the potential to recognize billions of different antigens
Antibody
Y-shaped antigen receptor (protein), made only by B cells, that binds only to the antigen that prompted its synthesis
Activates complement, facilitates phagocytosis, or neutralizes pathogens or toxins

6. Five Classes of Antibodies
Constant regions determine 5 classes of antibodies (immunoglobins IgG, IgA, IgE, IgM, and IgD), each with different functions
B cell receptors are membrane-bound IgM or IgD antibodies

7. Different Immunoglobulins

8. Five Classes of Antibodies

9. How Abs work Some act as labels to identify antigens for phagocytes
Some work as antitoxins i.e. they block toxins for e.g. those causing diphtheria and tetanus
Some attach to bacterial flagella making them less active and easier for phagocytes to engulf
Some cause agglutination (clumping together) of bacteria making them less likely to spread

10. Number of ag binding sites Site of action Functions
Type
Number of ag binding sites
Site of action
Functions
IgG 2
Blood
Tissue fluid
CAN CROSS PLACENTA
Increase macrophage activity
Antitoxins
Agglutination
IgM 10
IgA
2 or 4
Secretions (saliva, tears, small intestine, vaginal, prostate, nasal, breast milk)
Stop bacteria adhering to host cells
Prevents bacteria forming colonies on mucous membranes
IgE
Tissues
Activate mast cells
 HISTAMINE
Worm response