Component of HUMORAL IMMUNITY –Anti bodies 1. Each antibody molecule is made of 2 heavy chains and 2 light chains ,Held together b...
Component of HUMORAL IMMUNITY –Anti bodies
1. Each antibody molecule is made of 2 heavy chains and 2 light chains ,Held together by disulphide bonds
2. divided into CLASSES or ISOTYPES by type of heavy chains
3. each antibody has an
- antigen binding portion(Paratope)
- functional portion(can fix complement, attach to phagocytes and activate NK cells)
1. Antibodies recognize antigens that are three-dimensional in a 'lock and key' manner.
2. They can recognize soluble or cell surface antigens.
3. They can recognize antigens that are proteins, carbohydrates, lipids or nucleic acids.
4. The first antibody to he secreted is IgM
5. Then, under the influence of cytokines by T helper cells, the B cells switches to secreting IgG,IgA or IgE
6. This is called ISOTYPE SWITCHING.
| IgE | IgG | IgA | IgM | |
| Form | Monomer | Monomer | Dimmer | Pentamer |
| Hervey chain | £ | γ | α | µ |
| Placental transfer | - | + (passive immunity lasts for 3-6 months) | - | - |
| Present in secretion | - | Milk | Mucus(RS,GIT,GUT), gastric fluid ,tears ,saliva , Milk (colostrums) | Mucus Surface of B lymphocytes |
| Main Function | Protection against parasites | Transfer immunity to fetus | Locally protect from infection | Agglutinating bacteria |
| Other features | Type 1 hypersensitivity | Found ↑ [ ] in Body fluid Main antibody produce in 2ry response | Major antibody found in external secretion | 1st antibody produce in immune response |
ACTIONS OF ANTIBODIES:
Antibodies are secreted by plasma cells and circulate in the blood to the site of infection to eliminate the antigen.
Antibodies can do the flowing to help protect against infections.
1) Neutralization of toxins: so Own they cannot act on cells
2) Neutralization of viruses so that they cannot bind to cellular receptors and enter cells.
3) Agglutination/ immobilization/ of bacteria and viruses
4) Opsonisation of bacteria arid viruses
5) Activation of the classical complement pathway
6) Antibody dependent cellular cytotoxicity by NK cells
7) Mast cell degranulation to promote acute inflammation
