Chapter 13: The Human Immune System Flashcards
first line of nonspecific defense
- barrier that prevents pathogens from entering the body
- skin
- mucous membranes, which release mucus with antimicrobial substances such as lysozymes
- cilia in the respiratory system to sweep out mucus with microbes
- stomach acid
second line of nonspecific defense
- goal: limit spread of invaders
- inflammatory response, phagocytes, complement, interferons, natural killer cells
inflammatory response
- histamine triggers vasodilation (enlargement of blood vessels) that brings more blood, and then phagocytes secreted by basophils (white blood cells) and mast cells
- pyrogens: released by leukocytes, increase body temperature
phagocytes
- ingest invading fungal and bacterial microbes
- 2 types: neutrophils and macrophages (both migrate to infected site based on chemical attractants)
- neutrophils: engulf microbes and die after a few days
- macrophages: transform from monocytes, extend pseudopods, and engulf huge numbers of microbes over a long period of time with lysozymes and toxic oxygen
complement
-group of proteins tat leads to lysis of invading cells
interferons
-block cell-to-cell viral infections
natural killer (NK) cells
-destroy virus-infected body cells (as well as cancerous cells) by attacking the cell membrane, causing it to lyse
adaptive (specific) defense
- B lymphocyte and T lymphocytes arise from stem cells in the bone marrow
- B mature in bone marrow, T mature in the thymus gland
- travel in body recognizing specific antigens
adaptive immune response
- recognition: antigen receptors on B and T lymphocytes recognize specific antigens or epitopes (accessible part of antigen that lymphocytes bind to) by binding to them
a. lymphocytes must be presented antigen on antigen-presenting cell (macrophages, dendritic cells, sometimes B cells)
b. B cells are specific to one epitope - activation phase: lymphocytes undergo rapid cell division, forming effector and memory cells (responsible for immunological memory)
- effector phase: B cells produce humoral response of producing antibodies and T-cells engage in cell-mediated response
T lymphocytes
- recognize and bind to antigens that are displayed on APCs by MHC molecule
- once activated, T cell proliferates to form active T clones, some which become memory, some effector cells
- two types: helper T cells and cytotoxic T cells
helper T cells
- activated by interaction with antigen-presenting cells
- activates cytotoxic T cells, other helper T cells, and B cells that rproduce antibodies
- trigger both humoral and cell-mediated responses
- AKA CD4 cells
cytotoxic T cells
- attack and kill infected or cancerous body cells
- cell-mediate humoral response: release perforin and granzymes that cause cell to die
- AKA CD8 cells
B lymphocytes
- has antigen receptors (Y-shaped molecule consisting of 4 polypeptide chains, 2 light and 2 heavy, 4 constant regions, 4 variable regions) on its surface
- antibodies: soluble forms of antigen receptors
- humoral immune response: produce antibodies (immunoglobins)
- activation
- APC presents antigen or epitope on its cell surface using class II MHC
- helper T recognizes epitope-MHC molecule complex and is actiavted by cytokines secreted from APC
- produces clone: some become effector cells (plasma cells) that secrete antibodies, others become memory cells
self-tolerance
-immune system often doesnt attack its own body cells
auto-immune disease
-does not exhibit self-tolerance, but rather lymphocytes have receptors for their own body cells
self-reactivity
- lymphocytes tested in bone marrow
- if self-reactive, they will be destroyed by apoptosis
regulatory T cells
-inhibit the activation of the immune system in response to self-antigens
MHC molecules
- cell surface molecules that identify the cells as self
- class I: surface of every nucleated body cell
- class II: found on specialized cells, such as macrophages, B cells, dendritic cells, and activated T cells
antigen-presenting cells (APC)
- ex: macrophage, dendrite, b cell
- either becomes infected with antigen or engulfs it
- once inside host, enzymes break down into fragments, and attach them to a MHC molecule, ehich then moves to the surface of the molecule and presents it
clonal selection
- fundamental mechanism in the development of immunity
- means by which one particular lymphocyte that matches a specific antigen or epitope (antigenic determinant)is identified and activated
- process of antibodies being chosen from a limitless variety
passive immunity
- temporary
- antibodies are transferred to an individual from someone else (from mother or injections)
active immunity
- permanent
- individual makes his or her own antibodies after being ill and recovering or after being vaccinated
vaccine
-dead or live viruses or enough of the outer coat of a virus to stimulate a full immune response that causes lifelong immunity
blood type
- A: A antigen and B antibodies
- B: B antigen and A antibodies
universal donor
-O: no antigens and A and B antibodies
universal recipient
-AB: no antibodies, A and B antigens
Rh factor
-antigen on surface of red blood cells, is either positive or negative
HIV
- retrovirus that attacks CD4 molecules, mainly helper T cells
- leads to AIDS
allergens
- cause allergies through hypersensitivity
- release of histamine, an anti-inflammatory agent
important characteristics of immun system
- specificity
- diversity
- memory
- distinguish self from nonself
