**Plasma Cells: The Cells that Secrete Antibodies**

Plasma cells are a specialized type of white blood cell called B lymphocytes (B cells) that play a crucial role in the immune response. These cells are responsible for producing and secreting antibodies, also known as immunoglobulins.

**Function of Plasma Cells**

Plasma cells are an essential component of the humoral immune response, which involves the production and circulation of antibodies in the body. Antibodies are proteins that are specific to a particular antigen (foreign substance) and help in neutralizing or eliminating these antigens.

The main function of plasma cells is to produce and secrete large quantities of antibodies into the bloodstream and other body fluids, such as saliva, mucus, and tears. These antibodies then bind to the specific antigens and mark them for destruction by other immune cells, such as phagocytes or natural killer cells.

**Characteristics of Plasma Cells**

Plasma cells are derived from B cells that have encountered an antigen and undergone a process called B cell activation. Once activated, B cells differentiate into plasma cells, which have several distinguishing features:

1. **Abundant cytoplasm:** Plasma cells have a large amount of cytoplasm filled with rough endoplasmic reticulum (ER), which is responsible for synthesizing and processing antibodies.

2. **Clock-face nucleus:** The nucleus of a plasma cell is often described as having a clock-face appearance due to the eccentric arrangement of heterochromatin, giving the nucleus a speckled or clumped appearance.

3. **Golgi apparatus:** Plasma cells also have a well-developed Golgi apparatus, which is involved in packaging and modifying the antibodies before they are secreted.

4. **Antibody secretion:** The specialized machinery within plasma cells enables them to produce and secrete large quantities of antibodies. These antibodies are released into the bloodstream and other body fluids to combat the specific antigen that triggered the immune response.

**Conclusion**
In summary, plasma cells are the cells of connective tissue that secrete antibodies. They are derived from B cells and play a crucial role in the humoral immune response by producing and releasing antibodies into the body fluids to neutralize or eliminate specific antigens.