Question

How does our immune system work?

Answer 1

Immune system refers to the organization of the immune organs, cells and biomolecules that prevent the organism from developing a disease. These are nothing but defence systems just like how our soldiers fight at the borders preventing enemies from coming into the country. Our immune system fights with the disease causing organisms and keeps our body healthy.

Complete solution:
The study of the immune system is called immunology. Our immune system consists of organs , cells and biomolecules required to fight against the germs.
A) Lines of defence:
Our body protects us from diseases in various ways. Firstly, it stops the entering of microbes from the physical level,like skin,mucous membranes and lysozyme present in saliva, sweat, tears etc. This is the first line of defence.
Even if entry has occurred in spite of the first line of defence, our cells of the immune system will produce Fever,inflammation,antimicrobial substances,phagocytes etc that prevent growth of microbes. This is the second line of disease.
Even if the second line of defence doesn’t work, then specific antibodies against the antigens of microbes are produced. B lymphocytes are associated with this. This is the third line of defence and if this fails, we get disease.
B) Organs of immune system:
Bone Marrow: Bone marrow is required for the maturation of B-lymphocytes
Thymus: T-Lymphocytes mature in thymus, a flat bilobed organ situated below the thyroid gland, above the heart.
Lymph Nodes: They are bean shaped structures containing lymphocytes, macrophages and dendritic cells.
Spleen: Spleen filters the blood and hence encounters systemic infections. It is a large oval organ present in the left abdominal cavity.
Mucosa Associated Lymphoid tissue: This is a tissue and is not developed into an organ.It is associated with mucosa of different tracts and helps in inflammation during infection.
C) Cells:
The main part of the immune system are the white blood cells or leukocytes.They help in non-specific immunity. There are five types of leukocytes:
1. Macrophages(monocytes):They ingest bacteria,foreign cells,damaged and dead cells.
2. Neutrophils: Neutrophils contain granules that release enzymes to help kill and digest bacteria and other foreign cells.
3. Eosinophils: They attach to bacteria, immobilize them and kill.
4. Basophils: Basophils release histamine during allergic reactions
Complement System: It consists of about 30-40 proteins that activate one other in a sequence that may kill bacteria or help other cells to do so.
Cytokines: they act as messengers of the immune system, helping WBCs reach the area of infection.
D) Mechanism of immune action:
B-lymphocytes are capable of producing antibodies and they display on membrane surfaces.when the antigen comes near it , they capture the circulating antigens. They reach the spleen, lymph nodes and become memory cells and plasma cells. The memory cells store information about specific antigens and show quick responses. T-lymphocytes are concerned with cell mediated immunity or non specific immunity.They cannot recognize antigens or produce antibodies.
Entering of microbe –> first line of defence ->second line ->antibody production -> recognizing antigens ->phagocytosis.

Note:
The main function of the immune system is to prevent the microbes from entering and killing them if they do. The main principle of vaccines is based on the fact that our immune cells produce antibodies and other substances by recognizing proteins or DNA of microbes and kill them quickly using memory cells. Edward Jenner was the first person to pioneer vaccines, he also developed vaccines for smallpox.