Explain the role of white blood cells in the body's defense against foreign substances.
Since Jiskha doesn't have a biology expert at this time, please try posting your question at this site.
http://www.biology-online.org/biology-forum/
it engulves harmful micro organisms and destroy them a process called phagocytosis and fight against diseases
White blood cells, also known as leukocytes, play a vital role in the body's defense against foreign substances such as bacteria, viruses, and other harmful microorganisms. They are an essential component of the immune system, which is responsible for protecting the body from infections and diseases.
To understand their role, let's start with the types of white blood cells involved in the defense mechanism:
1. Neutrophils: These are the most abundant white blood cells and are the first to arrive at the site of infection. They engulf and destroy bacteria and other foreign substances through a process called phagocytosis.
2. Lymphocytes: These cells are mainly responsible for adaptive immunity, which involves the body's ability to recognize and mount a specific response against a particular pathogen. There are two primary types of lymphocytes:
- B cells: They produce antibodies that bind to the surface of foreign substances, marking them for destruction by other immune cells.
- T cells: They directly attack infected cells or foreign substances.
3. Monocytes: They circulate in the bloodstream but eventually migrate into the tissues, where they differentiate into specialized cells called macrophages. Macrophages are highly phagocytic and can engulf and destroy foreign substances.
Now, let's see how white blood cells act in the body's defense:
1. Recognition: White blood cells have specialized receptors on their surfaces that enable them to identify foreign substances. These receptors can recognize specific molecules, called antigens, which are unique to different pathogens.
2. Recruitment: When an infection occurs, white blood cells are recruited to the site of infection through a process called chemotaxis. Chemical signals released by damaged tissues and other immune cells attract white blood cells to the affected area.
3. Phagocytosis: Neutrophils and macrophages employ phagocytosis to engulf and destroy foreign substances. They surround the pathogen, form a membrane-bound vesicle called a phagosome, and release powerful enzymes that break down the engulfed material.
4. Antibody production: B cells produce antibodies that bind to specific antigens on the surface of pathogens. These antibodies neutralize the pathogen's harmful effects and can also mark them for destruction by phagocytic cells or activate other components of the immune system.
5. Cell-mediated immunity: T cells recognize and directly attack infected cells or cells carrying antigens on their surface. This mechanism is crucial for eliminating intracellular pathogens or cancer cells.
In summary, white blood cells play various roles in the body's defense against foreign substances. Through phagocytosis, antibody production, and cell-mediated immunity, they help identify, neutralize, and eliminate invading pathogens, thereby preserving our health and well-being.