There are many different types of white blood cells that play a role in the immune response. We’ll talk about the two main types here:
- General responders: cells that recognize the antigens on the surface of bacteria, viruses, and other invaders and quickly destroy them. These cells don’t discriminate among different threats in your body; they just launch an all-out attack. This is known as a generalized immune response. Some of these cells also help pave the way for a more targeted response to specific bacteria, viruses, and other unwanted materials.
- Targeted responders: cells known as lymphocytes, which target invaders by producing proteins called antibodies that target specific antigens. This process is a targeted or specific immune response. Each antigen that enters your body has an antibody targeted to it. Your body remembers which antibody will destroy a certain intruder, which creates a quicker immune response in the future.
Examples of cells involved in generalized immune response include:
- Neutrophils: These white blood cells are among the first to travel to a site of infection. They can ingest the invading microorganisms while also releasing special proteins called enzymes that help destroy them.
- Monocytes and macrophages: Monocytes are white blood cells that are made in the bone marrow and then travel through the bloodstream to different tissues and organs. There they become macrophages, which can surround and devour unwanted cells. Monocytes and macrophages also are able to carry antigens from these unwanted cells on their surfaces, so that your body’s lymphocytes can see them and begin launching a specific immune response. Because of this ability, monocytes and macrophages are also called antigen-presenting cells.
- Dendritic cells: Dendritic cells are found in the bloodstream, skin, and other tissues. They are powerful antigen-presenting cells that can find foreign invaders in the body, devour them, and then “offer up” those unwanted cells’ antigens on their surfaces. Dendritic cells move into areas where lymphocytes are concentrated, such as the lymph nodes and spleen, and trigger them to launch a specific immune response against those antigens.
Lymphocytes are white blood cells responsible for the more targeted immune response. They include:
- B cells: B cells are made in the bone marrow and then collect in the lymph nodes and other areas of lymphoid tissue throughout the body. They can’t destroy unwanted materials themselves; instead, they make the antibodies that recognize and attach to a specific antigen. These antibodies either destroy the antigens or tell other immune cells, such as T cells, to do so.
T cells: T cells also form in the bone marrow, then move into the thymus gland behind the breastbone to mature. They gather in the lymph nodes and spleen, where they can recognize and react to specific viruses and other unwanted cells, much like antibodies do. Some T cells are responsible for managing the overall immune response instead of targeting harmful substances themselves. There are three types of T cells:
- Killer T cells destroy unwanted materials. When they encounter antigens attached to harmful invaders, they kill the invaders. Examples include viruses and cells that are undergoing pre-cancerous changes, but are not quite cancer.
- Helper T cells produce substances that help B cells and killer T cells work better, although they don’t destroy harmful invaders themselves.
- Regulatory (suppressor) T cells prevent the immune system from overreacting and attacking healthy tissues throughout the body.
- NK or “natural killer” cells: NK cells contain proteins known as enzymes that can kill potentially harmful materials. They’re not as “picky” as T cells because they don’t require specific antigens to launch them into action. As a result, they can take care of a wider range of foreign substances.