White Blood Cells and Their Types
White blood cells (WBCs), also known as leukocytes, are an essential part of the immune system. They play a crucial role in protecting the body against infections and diseases. There are several types of white blood cells, including T cells, B cells, and natural killer cells.

T Cells
T cells are a type of lymphocyte, a subtype of white blood cells. They are derived from the bone marrow and mature in the thymus gland. T cells are primarily responsible for cell-mediated immunity, which involves the direct targeting and destruction of infected or abnormal cells.

- T cells can recognize and bind to specific antigens (foreign substances) present on the surface of infected or cancerous cells.
- They can differentiate into different types of T cells, such as helper T cells, cytotoxic T cells, and regulatory T cells, each with specialized functions.
- Helper T cells assist other immune cells in their activities, such as activating B cells to produce antibodies or enhancing the activity of cytotoxic T cells.
- Cytotoxic T cells directly attack and destroy infected or abnormal cells.
- Regulatory T cells help maintain immune system balance and prevent excessive immune responses.

B Cells
B cells are another type of lymphocyte. They are responsible for humoral immunity, which involves the production of antibodies to neutralize harmful substances. B cells are produced in the bone marrow and mature in the lymphoid tissues.

- B cells can recognize specific antigens and produce antibodies that bind to these antigens, marking them for destruction.
- When a B cell encounters an antigen that matches its specific receptors, it undergoes activation and differentiation into plasma cells.
- Plasma cells are responsible for producing large quantities of antibodies that circulate in the bloodstream and tissues.
- Antibodies can neutralize pathogens, promote their recognition by other immune cells, and activate the complement system for further destruction.

Natural Killer Cells
Natural killer (NK) cells are a type of lymphocyte that belongs to the innate immune system. Unlike T and B cells, NK cells do not require prior exposure to antigens for activation. They are primarily involved in the recognition and elimination of virus-infected cells and tumor cells.

- NK cells can directly recognize and kill infected or abnormal cells without the need for specific antigen recognition.
- They release cytotoxic granules containing perforin and granzymes, which induce programmed cell death in their targets.
- NK cells also produce cytokines that enhance the immune response and recruit other immune cells to the site of infection or inflammation.

Conclusion
In summary, T cells, B cells, and natural killer cells are all types of white blood cells involved in different aspects of the immune response. T cells mediate cell-mediated immunity, B cells are responsible for humoral immunity through antibody production, and NK cells provide innate immunity by directly targeting infected or abnormal cells.