The Immune System Flashcards
Nonspecific: First Line of Defense
A barrier that helps prevent pathogens from entering the body. These include; skin, mucous membranes which release mucus with antimicrobial substances, cilia that sweep out mucus and stomach acid.
Nonspecific: Second Line of Defense
Limit the spread of invaders in advance of specific immune responses. It includes inflammatory responses, phagocytes, complement, interferons and natural killer cells.
Inflammatory Response
Histamine, released by basophils and mast cells in the connective tissue, trigger vasodilation which increases blood supply to the area and bring more phagocytes. Prostaglandins, chemokines and pyrogens also play a role.
Vasodilation
enlargement of blood vessles
Basophils
a type of circulating white blood cell
Prostaglandins
promote blood flow during an inflammatory response
Chemokines
secreted by blood vessel endothelium and monocytes attract phagocytes to the area
Pyrogens
released by certain leukocytes; increase body temperature to speed up the immune system and make it more difficult for microbes to function
Phagocytes
Ingest invading microbes. Neutrophils and monocytes move to the area in response to chemical attractions called chemotaxis. Neutrophils engulf microbes and die within a few days. Monocytes transform into macrophages, extend pseudopods and engulf huge numbers over a long period of time. They digest with a combination of lysozyme, superoxide anion and nitric oxide.
Complement
A group of proteins that lead to the lysis of invading cells.
Interferons
block against cell-to-cell viral infections
Natural Killer Cells
destroy virus infected body cells or cancerous cells; they attack the cell membrane and cause it to lyse (burst) and die
Specific: Third Line of Defense
Relies on B and T lymphocytes. They both originate in the bone marrow and once mature they circulate in blood, lymph and lymphatic tissue. Bothe recognize specific antigens.
Antigens
substances that cause the production of antibodies
B Lymphocytes
Mature in the bone marrow and produce a humoral response by producing antibodies. They become stimulated by T lymphocytes or be free viruses and bacterial toxins found in the blood.
T Lymphocytes
Mature in the thyroid gland and produce a cell-mediate response. They are stimulated by body cells that have been infected and by antigen-presenting cells which display foreign substances on their surface cells. There are two types; cytotoxic T cells and helper T cells. Each responds to a different histocompatibility complex (MHC) molecule.
Cytotoxic T Cells
Kill body cells infected with viruses or pathogens or cancer cells. Their antigen receptors bing to protein fragment by class I MHC molecules. After binding, a CD8 surface protein holds the cells together until the T is activated. Then, after activation it differentiates into plasma cells and memory cells. Activated ones kill cells by releasing perforin and infecting microbes are released to the blood and killed by antibodies.
Perforin
Released by active cytotoxic T cells; forms pores in the target cell’s membrane
Helper T Cells
Announce to the immune system, with macrophages and B cells, that foreign antigens have entered the body. They bind to proteins displayed by Class II MHC molecules. After binding, CD4 holds the cells together until T is activated. After activation, it splits into memory and plasma cells. Helper cells stimulate other helpers, cytotoxic Ts and B cells by releasing cytokines, interleukin-1 and interleukin-2.
Major Histocompatibility Complex Molecules
Human Leukocyte Antigen; collection of surface markers that identify the cell. No two people, except twins, have the same markers.
Class I MHC Molecules
Found on almost all body cells.
Class II MHC Molecules
Found on specialized cells such as macrophages, B cells and activated T cells.
Clonal Selection
Mechanism in the development of immunity. Antigenic molecules bind to a B or T lymphocyte and after activation they proliferate into plasma or memory cells.
Plasma Cells
Short-lived and fight the antigen immediately in what is called a primary immune response.
Memory Cells
Long-lived cells that bear receptors specific to the same antigen as the plasma ells and remain circulating for a lifetime. If the body is attacked again by the same virus, memory cells rapidly reactivate. This is called the secondary immune response, is faster and greater magnitude than the primary one.
Immunological Memory
The capacity of the immune system to generate a secondary immune response. It is the basis of vaccinations.
How Macrophages Interact with the Immune System
A macrophage acts as an antigen-presenting cell engulfs a bacterium and present a fragment of it to the cell surface by an MHC molecule. A helper T cell is activated by binding to the MHC-antigen complex. The helper T cell proliferates and clones into copies with the same MHC-antigen combination. These clones secrete cytokines. Cytokines stimulate helper T cells, B cells and cytotoxic T cells.
Antibodies: Structure
Globular proteins; Y shaped with two identical, heavy polypeptide chains and two identical, light polypeptide chains joined by disulfide bridges; it consists of four constant regions and four variable regions and the tip of the Y are the binding sites for different antigens
Five Classes of Imunoglobins
IgM, IgA, IgD, IgE and IgG
Antibodies: Function
Antibodies neutralize the antigen by causing them to clump and form an antigen-antibody complex. This complex is then, phagocytosed by macrophages. OR complement fixation occurs and activation of a complement lysis the cells.
Antibody Variety
There is no viral disease for which humans cannot produce antibodies. Blueprints for antibodies are made early in life prior to exposure to antigenic agents.
Passive Immunity
Temporary; antibodies are transferred to an individual from someone else
Active Immunity
Permanent; An individual makes their own antibodies after immunization
Blood Donations
If the recipient has antibodies to the donor’s antigens there is a certain danger.
Cross-Match
The process by which a donor and recipient are mixed to determine compatibility.
Universal Donor
Blood Type O; it has no blood cell antigens to be clumped by the recipient’s blood
Universal Recipient
Blood Type AB; there are no antibodies to clump the donor’s blood
RH Factor
Antigen located on the surface of red blood cells; 85% of the population is RH+
Acquired Immune Deficiency Disorder
AIDS; Causes people to be highly susceptible to diseases, infections and cancers. The human immune deficiency virus causes AIDS and it attacks cells that bear CD4 molecules on their surface. HIV is a retrovirus.
Positive Feedback in the Immune System
When helper T cells are activated by class II MHC molecules, it releases cytokines which stimulates more helper T cells as well as B cells and Cytotoxic T cells.
Allergies
Hypersensitive responses to antigens. They involve the release of histamines which causes blood vessels to dilate.
Anaphylactic Shock
An acute, allergic response that can results in death within minutes.
Autoimmune Diseases
Immune systems that cannot distinguish between self and nonself. It perceives cell s in the body as nonself. Examples are lupus, arthritis and juvenile daibates
Multiple Sclerosis
Autoimmune Disease: the immune system attacks the myelin sheath surrounding neurons in the CNS
Monoclonal Antibodies
Antibody produced by a single B cell that have bee selected for a specific antigen. Important in research.
