Our Immune system has about a ton of cells– different types of cells with their own unique functions. One of such cells are lymphocytes.
What are lymphocytes?
The chief cells of the Immune system, the real soldiers of the inherent army of our body are known as lymphocytes. A healthy person has about a trillion lymphocytes in his body. There are two types of Lymphocytes:
- T lymphocytes (T cells) and
- B lymphocytes (B cells)
Where do they come from?
Like a majority of blood cells, these cells are produced in our bone marrow by a process called hematopoiesis (heamato means ‘blood’ and poeisis means ‘to make’). More specifically, the process may also be called lymphopoiesis.
Now, both these cells are produced in the bone marrow from pleuripotent stem cells. Each of these cell brothers have a destiny. Some of them go on to become thymocytes, also known as T cells and others stay for some more time and become B cells on maturation.
Those cells which go on to become thymocytes migrate to thymus gland to mature i.e. fully develop. After maturing, they migrate via blood and lymph to the secondary lymphoid organs which are the sites of lymphocytes activation that take place through interaction of surveillance cells with antigens; similar to a headquarter from which orders for action are given.
T lymphocytes generate cell-mediated immunity. Cell-mediated immunity is an immune response that does not involve administration of chemicals or bodily biological bombs or poison but actual deployment of other soldiers like macrophages to the site of infection. T lymphocytes called cytotoxic T-cells directly attack invading pathogens. They also destroy infected body cells and cancerous cells.
Antigen- presenting cells
There also exists a subgroup of T cells known as T helper cells, which interact specifically with the antigen and become activated. These cells now dispatch from the lymphoid tissues and circulate along with blood. These cells produce chemical substances called lymphokines (a kind of antigen poison) to eliminate the antigens.
Now B cells are also produced in the bone marrow, mature in the bone marrow itself for a greater period of time than T cells. However, after some time, they too migrate to secondary lymphoid organs to mature properly.
These B cells then perform the function of immune surveillance. They do not produce antibodies until they become fully activated.
Once these cells are activated, they produce and secrete a large amount of substances called antibodies which bind to the antigen; just like you add meat to make anything attractive for a dog.
Due to these antigens, a large amount of macrophages get attracted to the specific antigen and destroy it. They are also sometimes known as antibody factories.
Even B-cells are of various types. They are:
- Plasma B cells (also known as plasma cells, plasmocytes, and effector B cells);
- Memory B cells (Live for a long time and are responsible for maintaining all the data related to previous infections like type of virus, how it was eliminated, which antigens are produced, etc. and also for giving executable orders for recurring infections);
- B-1 cells;
- B-2 cells;
- Marginal-zone B cells, and
- Follicular B Cells.