immune disorders
Overview of the Immune System
Components of the Immune System
The immune system has many components: Antibodies (immunoglobulins) Innate Immunity None B cells (B lymphocytes) Basophils None Cellsare the smallest unit of a living organism, composed of a nucleus and cytoplasm surrounded by a membrane. Chemotaxisis the process of by which a chemical substance attracts cells to a particular site. Complement System None Cytokines None Dendritic Cells None Eosinophils None Helper T cellsare white blood cells that help B cells produce antibodies against foreign antigens, help killer T cells become active, and stimulate macrophages, enabling them to ingest infected or abnormal cells more efficiently. Histocompatibility(literally, compatibility of tissue) is determined by human leukocyte antigens (self-identification molecules). Histocompatibility is used to determine whether a transplanted tissue or organ will be accepted by the recipient. Human leukocyte antigens (HLA)are a group of identification molecules located on the surface of all cells in a combination that is almost unique for each person, thereby enabling the body to distinguish self from nonself. This group of identification molecules is also called the major histocompatibility complex. Animmune complexis an antibody attached to an antigen. Animmune responseis the reaction of the immune system to an antigen. Immunoglobulinis another name for antibody. Interleukinis a type of messenger (cytokine) secreted by some white blood cells to affect other white blood cells. Killer (cytotoxic) T cellsare T cells that attach to infected cells and cancer cells and kill them. Leukocyteis another name for a white blood cell, such as a monocyte, a neutrophil, an eosinophil, a basophil, or a lymphocyte (a B cell or T cell). Lymphatic System: Helping Defend Against Infection None Lymphocytes None Monocytes and Macrophages None Major histocompatibility complex (MHC)is a synonym for human leukocyte antigens. Mast cellsare cells in tissues that release histamine and other substances involved in inflammatory and allergic reactions. Amoleculeis a group of atoms chemically combined to form a unique substance. Natural killer cellsare a type of white blood cell that can recognize and kill abnormal cells, such as certain infected cells and cancer cells, without having to first learn that the cells are abnormal. Neutrophils None Phagocytesare a type of cell that ingests and kills or destroys invading microorganisms, other cells, and cell fragments. Phagocytes include neutrophils and macrophages. Phagocytosisis the process of a cell engulfing and ingesting an invading microorganism, another cell, or a cell fragment. Areceptoris a molecule on a cell’s surface or inside the cell that can identify specific molecules, which fit precisely in it—as a key fits in its lock. Regulatory (suppressor) T cellsare white blood cells that help end an immune response. T cells (T lymphocytes) White blood cells None 