If we go back to the stage of the battle when the Helper T Cells called for backup. This would have meant a whole team of B Lymphocytes will have arrived. These are like special forces, they don't attack the bad guys directly- instead they do it 'remotely'. B Cells produce Y and T shaped grenades known as antibodies which attach to foreign antigens of baddies. Once these B Soldier see antigens they multiply quickly and develop in plasma cells , which are the main antibody production cells. And memory cells are produced so another invasion in the future can be prepared for...
The lymph nodes are vital to the body's defence system - they produce and harbour immune cells (lymphocytes) that protect the body from disease.
Lymph nodes are scattered throughout the body and also concentrated in groups. Each node is a mass of lymphatic tissue divided into compartments by partitions of connective tissue known as trabeculae. Lymph fluid from most tissues or organs flows through one or more lymph nodes, where it is filtered and cleaned, before draining into the venous blood stream. Several smaller lymphatic vessels bring lymph to the node, and one larger vessel carries it away. The lymph vessels have valves to ensure one-way flow of fluid.
Non-Specific Response
- The immune response involves attacks on specific microorganisms or the toxins they produce
- Non-Specific responses react to any kind of damage, such as a physical knock, a burn, extreme cold, corrosive chemicals, radiation, microbes, parasites, worms
- The main non-specific defensive response is inflammation
- Mast Cells in damaged tissue releases histamine which cause an acute inflammation involving pain, redness and swelling
- This attracts white blood cells
- The walls of capillaries, the smallest blood vessels at the site, become more permeable and porous to allow the passage of white blood cells, defensive chemicals, and fluids, which accumulate as the battle proceeds
- The white blood cells surround, engulf, and destroy invading pathogens
- The blood may also clot to form a barrier that not only seals the leak but also prevents further microbial penetration
Also involves
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Phagocytes- Large white blood cells which engulf foreign material
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Complement proteins- Several blood proteins that contribute to the breakdown and removal of pathogens
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Cytokines- Small proteins that, among other things, inhibit the reproduction of viruses
Specific Response
Specific responses may occur alongside non-specific reactions such as inflammation, or follow if the infection persists. There are two main types of specific defence: cell-mediated and antibody-mediated (humoral) immunity.
Both depend on the actions of lymphocytes of two different kinds - B and T lymphocytes
- B Cells make protein antibodies known as gamma globulins. These react against antigens (foreign protein substances), which differ from the body's own natural proteins. T Cells multiply and attack the pathogen cells.
Cell-Mediated Immunity
- Cellular immunity involves various types of T Lymphocytes
- Once a T Lymphocyte recognises the antigen, it multiplies rapidly
- Its offspring differentiate into several types
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Helper T Cells activate both B Cells to help antibody-mediated immunity and macrophages to engulf the microbes and debris
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Killer (cytotoxic) T Cells attack microorganisms as well as any body cells infected with them, using powerful proteins called lymphokines
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Suppressor T Cells inhibit the response of other cells to the invading microbes
Some T Cells retain memory of the antigen for future defence
Antibody-Mediated Immunity
- Whereas T Cells can attack invading organisms directly, B Lymphocytes do so 'remotely'
- They produce Y or T shaped chemical antibodies
- Each type of antibody acts against a certain type of microorganism or material by attaching to antigens on its surface
- The presence of antigens triggers B Cells to multiply
- Some develop in plasma cells, which are the main antibody producing cells
- Memory cells are produced, which can recognise the same antigen and initiate defence many years later
Phagocytosis
Engulfing Stage- The white cell extends pseudopods [which are like false feet] towards and around the unwanted item.
Lysis Stage- The items are trapped in a phagocytic vesicle, which with enzyme-containing lysosomes form phagolysosomes. Where lysis (breaking down) occurs.
Exocytosis stage- Harmless products of cell eating are expelled through the white blood cell's membrane, or in a tiny membrane bound exocytic vesicles to the extracellular fluid.
