1. White Blood Cells (Leukocytes):
* Neutrophils: The most abundant type of white blood cell, they are the first responders to infection. They engulf and destroy bacteria and fungi through a process called phagocytosis.
* Macrophages: These larger cells also phagocytize pathogens, but they also play a role in initiating an immune response by presenting antigens to other immune cells.
* Lymphocytes: These cells are responsible for the adaptive immune response.
* T lymphocytes (T cells): These cells recognize and kill infected cells.
* Helper T cells: Activate other immune cells.
* Cytotoxic T cells: Directly kill infected cells.
* B lymphocytes (B cells): These cells produce antibodies that bind to and neutralize pathogens.
2. Other Important Cells:
* Natural Killer (NK) Cells: These cells kill infected cells and tumor cells without the need for prior sensitization, part of the innate immune response.
* Dendritic Cells: These cells act like messengers, capturing antigens from pathogens and presenting them to T cells, initiating the adaptive immune response.
3. Key Molecules:
* Antibodies: These proteins produced by B cells specifically bind to antigens on pathogens, neutralizing them and marking them for destruction by other immune cells.
* Cytokines: These signaling molecules produced by immune cells communicate with other immune cells, coordinating the immune response.
This is just a brief overview of the complex and fascinating world of the immune system. It's important to remember that all of these cells work together in a highly regulated and coordinated manner to protect the body from infection.
