The second line of defence
The second line of defence is (like the first line of defence):
- innate: not learned and non-adaptive which means it cannot adjust
- non-specific: a response to a pathogen regardless of its type
The second line of defence takes action when the first line of defence has failed. It involves structures of the body and the cells they produce to act against antigens.
The body reacts in a number of ways to try and get rid of pathogens once they have entered the body, such as inflammation, fever, apoptosis, phagocytosis, interferon and complement.
The cells and their functions that are involved in the second line of defence are listed below:
- innate: not learned and non-adaptive which means it cannot adjust
- non-specific: a response to a pathogen regardless of its type
The second line of defence takes action when the first line of defence has failed. It involves structures of the body and the cells they produce to act against antigens.
The body reacts in a number of ways to try and get rid of pathogens once they have entered the body, such as inflammation, fever, apoptosis, phagocytosis, interferon and complement.
The cells and their functions that are involved in the second line of defence are listed below:
![Picture](/uploads/2/3/5/8/23585692/2826714.png?317)
Macrophages in action
As can be seen in the figure to the left, macrophages are responsible for engulfing and digesting infectious agents via phagocytosis. They are found in high amounts in the liver, lungs, kidneys, spleen and lymph nodes. Macrophages usually live for one month.
The process:
1. macrophage engulfs foreign material
2. foreign material is enclosed into a vesicle
3. the vesicle combines to a lysosome within the cell
4. lysosomes contain digestive enzymes which break down the foreign material
5. antigens of the foreign material are presented to the T-cell
As can be seen in the figure to the left, macrophages are responsible for engulfing and digesting infectious agents via phagocytosis. They are found in high amounts in the liver, lungs, kidneys, spleen and lymph nodes. Macrophages usually live for one month.
The process:
1. macrophage engulfs foreign material
2. foreign material is enclosed into a vesicle
3. the vesicle combines to a lysosome within the cell
4. lysosomes contain digestive enzymes which break down the foreign material
5. antigens of the foreign material are presented to the T-cell
Inflammatory response
Inflammation causes swelling, redness and pain. It occurs in tissues where cells have been damaged or killed due to invading pathogens or physical injuries. Histamine is released from cells (such as basophils) and promotes vasodilation, which is the widening of blood vessels, in the affected region. This causes an increase in blood flow and therefore cells (that use blood as a mode of transportation), and help to protect against infection. The swelling and redness is caused from the increase in blood flow.
Histamines also have the power to change the permeability of the blood vessels (that are present in the inflamed area) which makes it easier for cells that aid in the healing process (such as neutrophils and macrophages) to squeeze from them into the infected tissue. This process causes some pain which is necessary as it reduces voluntary movement therefore speeding up the healing process.
Inflammation causes swelling, redness and pain. It occurs in tissues where cells have been damaged or killed due to invading pathogens or physical injuries. Histamine is released from cells (such as basophils) and promotes vasodilation, which is the widening of blood vessels, in the affected region. This causes an increase in blood flow and therefore cells (that use blood as a mode of transportation), and help to protect against infection. The swelling and redness is caused from the increase in blood flow.
Histamines also have the power to change the permeability of the blood vessels (that are present in the inflamed area) which makes it easier for cells that aid in the healing process (such as neutrophils and macrophages) to squeeze from them into the infected tissue. This process causes some pain which is necessary as it reduces voluntary movement therefore speeding up the healing process.