Our Immune System

Our Immune System 

• The immune system includes a defense mechanism to protect the body against invasion of foreign agent.

• The resistance of the body towards the foreign agents and its toxin is known as immunity.

Cell involved in immune response

• Lymphocytes are functional units of the immune system. They produce antibodies against the neighbouring cell.

• These antibodies bind antigen and destroy the antigen. The defense mechanism that is mediated by the antibody is called as humoral immune response.

Read more about the Pathogen and how do they adapt in body of host.

• In some cases, Antibody is not produced by the lymphocytes against antigen whereas foreign agents are destroyed by the association of lymphocytes and macrophages. 

• Such type of defense mechanism is called cellular immune response.

Lymphoid organs

• There are lymphoids organ in body That also constitute our immune system.

• The thymus and bone marrow are primary lymphoid organs. B and T lymphocytes are produced in these organs.

• After the formation these lymphocytes are migrated in to secondary lymphoid organs. 

• Lymph node, tonsils, mucosa associated lymphoid tissue are common secondary lymphoid organs. 

• In foetal development, bone marrow is the dominant site of production of blood cells. 

• The bone marrow produces all lymphoid cells that are migrated to the thymus for maturation of T cells and formation of B cells.

Read about more about the Immunity : Active & Passive immunity 

• Thymus is another lymphoid organ, located at the lower part of the neck. 

• Thymus becomes more active during childhood time after which it  starts to degenerate and at the adult stage, it can be seen as rudimentary structure. 

• The function of thymus is production of T lymphocytes by proliferation of lymphocytes produced by the bone marrow.

• Lymph nodes are bean shaped structures located along the lymphatic system .

• Lymph nodes make filtration of foreign agents from lymph by phagocytic activity of macrophages and it also storage and proliferation Of  B and T lymphocytes.

• Spleen is large lymphoid organs. Spleen is the center where multiplication of B and T lymphocytes takes place. Spleen also helps in removal of debris and other dead particles from circulating blood. 

• Dead RBC are also removed by the spleen from circulating blood

• The main site of entry of microbes is through the mucosal epithelial cells so more than 50 % 0f lymphoid tissue is located within the lining of the major tract including respiratory, digestive and Genito- urinary tracts

• The  lymphoid tissue associated with mucosal lining is called as mucosa associated lymphoid tissue (MALT).

• The lymphoid tissue that is associated with the throat and nasal passage are known as Nasal  associated lymphoid tissue ( NALT).

• The lymphoid organs associated with gut are called gut associated lymphoid tissue (GALT).