The immune system is an inbuilt system in the human body that protects an organism against diseases. The structure and processes help prevent infectious diseases from harming the human body. Immunity is the state of protection against an infectious disease. Immune system is extremely essential for maintaining one’s health. People with low immunity fall prey to illness sooner than those with high immunity.
CELLS OF THE IMMUNE SYSTEM
The white blood cells, also known as the leukocytes, are the immune system cells that are involved in defending the body against any foreign materials and infectious disease that tried to harm our body by entering it. There are five different types of the leukocytes which are all produces and derived from hematopoietic stem cell which is a multi-potent cell in the bone marrow.
Lymphocytes are the central cells of the immune system which are responsible for the adaptive immunity. These are of three types- B cells, T cells and the natural killer cells. While B and T lymphocytes are a part of adaptive immune system (immunity gained after the encounter of a disease), the natural killer cells are a part of innate immune system (immunity which was from before only).
– B cells: These develop in the bone marrow of mammals. These provide humoral immune response.
– Killer T cells: These kill the cells that are virus infected or are damaged or even dysfunctional.
– Helper T cells: they help in regulation of innate and adaptive immune responses and make decisions regarding the response that should be used for a particular pathogen. These cannot kill or clear the pathogens directly so they control the immune response and give direction to the other cells for performing the tasks.
– Gamma delta T cells: these help in developing a memory phenotype. These help in adaptive immunity.
B lymphocytes and antibodies- the B cell is responsible for identifying the pathogen when the antibodies present on its surface bind to a foreign antigen. It then starts multiplying for secreting millions of the antibodies that recognises the antigen. Antibodies neutralize the challenges and bind the bacterial toxins to themselves and defeating them. They even interfere with the receptors used by the virus and bacteria for infecting cells.
Natural killer cells- these are also written as NK cells and they are a part of the innate immune system. It does not attack the invading microbes directly. They destroy the virus infected cells or the tumour cells.