Leukocytes

Definition

Leukocytes, also known as white blood cells, are immune cells that play a critical role in defending the body against infection and disease. They circulate in the blood and migrate to sites of infection or injury.

5 Must Know Facts For Your Next Test

1. There are five main types of leukocytes: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
2. Neutrophils are the most abundant type of leukocyte and are the first responders to microbial infection.
3. Lymphocytes include T cells, B cells, and natural killer cells, each playing distinct roles in adaptive immunity.
4. Monocytes mature into macrophages and dendritic cells which are key players in phagocytosis and antigen presentation.
5. Eosinophils and basophils are involved in combating multicellular parasites and allergic reactions.

Review Questions

• What are the five main types of leukocytes?
• Which type of leukocyte is the most abundant in the human body?
• How do monocytes contribute to the immune response once they mature?

Related terms

Phagocytosis: The process by which certain leukocytes engulf and digest microorganisms and cellular debris.

Antigen Presentation: The process by which macrophages or dendritic cells display foreign antigens on their surface to T cells.

Natural Killer Cells: A type of lymphocyte involved in recognizing and killing virus-infected cells or tumor cells without prior sensitization.