Lymphocytes | Small white blood cells found in all organs and tissues. There are 2 principal types: B lymphocytes (B cells), which mature in the bone marrow, and T lymphocytes (T cells), which mature in the thymus. |
B cells | These lymphocytes are responsible for the production of antibodies, an important part of the immune response. |
T cells | These lymphocytes include killer (cytotoxic) T cells, which detect and kill cells that are abnormal (such as cancer cells), and helper T cells, which help other lymphocytes mount an immune response. |
Antigens | Any substances that can induce an immune response. |
Antigen-presenting cells | Specialized cells that engulf antigens and process them so that they can be recognized by lymphocytes. |
Neutrophils | All-purpose scavenger cells that ingest and destroy antigens and cell debris. |
Macrophages | White blood cells that stimulate healing and remove antigens, injured cells, and neutrophils from tissue. |
Eosinophils | White blood cells that ingest bacteria and other foreign cells, participate in allergic reactions, and help destroy cancer cells. |
Mast cells | Cells that release histamine and other substances involved in allergic reactions. |
Cytokines | The immune system’s messengers, typically small proteins, which help regulate an immune response by delivering signals from one cell to another. |
Antibodies | Also called immunoglobulins, antibodies are proteins produced by B cells that interact with specific antigens. They can form immune complexes, label antigens for removal by other cells, or block the ability of a virus to enter its target cell. |