Immune System Learning Objectives
Factors that influence phagocytosis during the inflammation response
-Activated complement proteins further the release of histamine and help attract phagocytes. -Endothelial cells secrete signaling molecules that attract neutrophills and macrophages.
Class 1 MHC
-Found on almost all cells of the body. -Bind to peptide fragments of foreign antigens synthesized within the cell. -Any body cell that becomes infected or cancerous can synthesize foreign antigens and display antigen fragments by virtue of its class 1 MHC molecules. -Class 1 MHC molecules that display bound antigen fragments are recognized by a subgroup of T cells called cytotoxic T cells. (refers to their use of toxic gene products to kill infected cells).
Describe the infectious agent that causes AIDS and explain how it enters a susceptible cell.
-HIV leads to AIDS -People without T cells cannot mount an effective Cytotoxic or B cell response
Roles of helper T lymphocytes in both humoral and cell-mediated immunity
-Humoral response relies mainly on B cells to present antigens to helper T cells. -To activate the cytotoxic T cells (main part of cell-mediated immunity), they require signals from helper T cells and an interaction with an antigen-presenting cell.
Distinguish between inborn and acquired immunodeficiency
-Inborn immunodeficiencies result from defects in the development of various immune system cells or defects in the production of specific proteins. ---Acquired immunodeficiencies are immune dysfunction that develops later in life and can be caused by exposure to a number of agents such as drug or viruses
Humoral immune response
-Involves the activatoin and clonal selection of efector B cells --> Secrete antibodies that circulate in the blood and lymph. -Name because blood and lymph were long ago called humors. -Also called the antibody-mediated response because of the key role of antibodies.
Class 2 MHC
-Made by just a few cell types. Dendritic cells, macrophages, and B cells --> Known as antigen-presenting cells because of their key role in displaying such internalized antigens. Antigen presenting cells display antigens for recognition by cytotoxic T cells and helper T cells (a group of T cells that assist both B cells and Cytotoxic T cells). In these cells, Class 2 MHC cells typically bind to antigen fragments derived from foreign materials that have been internalized through phagocytosis or endocytosis.
Describe the roles of antimicrobial proteins in innate immunity
-The larger antimicrobial proteins are often lytic enzymes, nutrient-binding proteins or contain sites that target specific microbial macromolecules. -The smaller antimicrobial peptides act largely by disrupting the structure or function of microbial cell membranes.
Explain how HIV infection eventually leads to a completely diminished acquired immune response.
-The virus infects and destroys helper T cells -Binds to CD 4 molecules on helper T cell membrane, then enters the cell
Explain what causes anaphylactic shock and how it can be treated
-acute allergic response • -widespread mast cell degranulation • -abrupt dilation • -drop in blood pressure • -death within minutes • Individuals may carry syringes containing the hormone epinephrine, which counteracts this response.
Distinguish between antigens and antibodies
-antigens are things like viruses -antibodies fight viruses
antigen vs. epitope
-epitope: the small, accessible portion of an antigen that binds to an antigen receptor; a single antigen usually has several different epitopes, each binding a receptor with a different specificity -because all antigen receptors produced by a single B or T cell are identical, they bind to the same epitope. Each B cell or T cell thus displays specificity for a particular epitope, enabling it to respond to any pathogen that produces molecules containing that same epitope
Describe an allergic reaction, including the roles of IgE, mast cells, and histamine.
-exaggerated response to allergens - plasma cells secret IgE -attach to mast cells • antigens bind to IgE -induce release of histamine An allergic reaction is a hypersensitive response to certain antigens called allergens. IgE antibodies are secreted by the plasma cells and attach by their tails to mast cells present in connective tissues. Later, when allergens enter the body, they attach to the antigen-binding sites of mast cell-associated IgE. this induces the mast cell to release histamine and other inflammatory agents from their granules.
List three autoimmune disorders and describe possible mechanisms of autoimmunity
-lupus and rheumatoid arthritis - multiple sclerosis -self-reactive lymphocytes Autoimmune diseases are causes by self-reactive lymphocytes that were not eliminated because of a failure in immune system regulation
Explain how the physical barrier of skin is reinforced by chemical defenses
In your sweat and tears there is lysozyme which is an antibacterial protein.
Explain what is done medically to reduce the risk of tissue transplant rejection due to differences in the MHC.
use closely matching tissue • immunosuppressants • bone marrow itself is rejected • graft versus host reaction
Explain how interferons limit cell-to-cell spread of viruses.
Interferons are proteins that provide innate defense by interfering with viral infections. virus-infected body cells secrete interferons, which induce nearby uninfected cells to produce substances that inhibit viral reproduction. In this way, interferons limit the cell-to-cell spread of viruses in the body, helping control viral infections
Cell-Mediated immune response
Involves the activation and clonal selection of cytotoxic T cells. Identify and destroy the target cells.
Memory Cell
Long lived cells that bear receptors specific for the antigen. Less numerous.
Monoclonal Antibodies
Monoclonal antibodies are antibodies that are made by identical immune cells that are all clones of a unique parent cell. Monoclonal antibodies can have monovalent affinity, in that they bind to the same epitope.
Define phagocytosis. Name four types of phagocytic leukocytes.
Phagocytosis: the cellular ingestion and digestion of bacteria and other foreign substances
How do phagocytic leukocytes recognize microbes?
Recognize them by use of Toll-like receptors (TLR). TLR recognizes fragments of molecules characteristic of a set of pathogens.
Effector Cell
Short lived cells that attack the antigen and any pathogens that are producing the antigen.
Describe some of the mechanisms that pathogens have evolved to thwart the immune response of their hosts.
Some pathogens avoid destruction by modifying their surface to prevent recognition or by resisting breakdown following phagocytosis Tuberculosis (TB) is one such disease and kills more than a million people a year
Secondary Immune Response
The acquired immune response elicited on second or subsequent exposure to a particular antigen. More rapid, of greater magnitude, and of longer duration than the primary immune response.
Primary Immune Response
The initial acquired immune response to an antigen. Appears after a lag of about 10-17 days.
Clonal Selection
The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for hte stimulating agent.
Cellular Basis for Immunological memory
The response to an antigen that has been encountered previously is stronger and more rapid that the initial response. The antigens are quicker at recognizing cells that have been in the body before.
Distinguish between the variable (V) and constant (C) regions of an antigen receptor.
The variable region has an amino acid sequence that varies extensively from one B cell to another. The constant region has an amino acid sequence that is the same for all antibodies.
Explain how the action of natural killer cells differs from the action of phagocytes.
cells that circulate through the body and detect the abnormal array of surface proteins characteristic of some virus-infected and cancerous cells; they do no engulf stricken cells, but instead release chemicals that lead to cell death, inhibiting further spread of the virus or cancer
Passive Immunity
immune response which involves antibodies obtained from outside the body
Describe the inflammation response, including how it is triggered
inflammation response is the changes brought about by signaling molecules released upon injury or infection. Histamine (signaling molecule released by mast cells) is released at sites of damage triggers nearby blood vessels to dilate and become more permeable. Activated macrophages and neutrophils discharge cytokines, signaling molecules that enhance the immune response. These cytokines promote blood flow to the site of injury/infection. The increase in local blood supply causes the redness and increased skin temperature typical of the inflammatory response. Blood- engorged capillaries lead fluid into neighboring tissues, causing swelling. During inflammation, cycles of signaling and response transform the site. Activated complement proteins promote further release of histamine, attracting more phagocytic cells that enter injured tissues and carry out additional phagocytosis. At the same time, enhanced blood flow to the site helps deliver antimicrobial peptides. The result is an accumulation of pus, a fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues.
Distinguish between innate immune response and acquired immunity
innate: first and second line of defense, not learned, natural response acquired: third line of defense, learned or adapted
B lymphocytes vs. T lymphocytes
lymphocytes: white blood cells that originate from stem cells in the bone marrow. T cells: lymphocytes that migrate from the bone marrow to the thymus, an organ in the thoracic cavity above the heart; antigen receptors of T cells bind only to fragments of ntigens that are displayed on the surface of host cells (the host protein that displays the antigen fragment on the cell surface is called an MHC molecules) B cells: lymphocytes that remain and mature in the bone marrow; antigen receptors of B cells bind to epitopes of intact antigens circulating in body fluids
Describe septic shock
occurs when chemicals that fight infection by triggering inflammatory reactions are released into the bloodstream. ... Sepsis is when the infection reaches the bloodstream and causes inflammation in the body.
Neutralization
refers to the ability of antibodies to block the site(s) on bacteria or viruses that they use to enter their target cell. One example of this within biology is a neutralizing antibody.
Name four types of phagocytic leukocytes
1.) Neutrophils: circulate in the blood and are attracted by signals from infected tissues and then engulf and destroy the infecting pathogens 2.) Macrophages: larger phagocytotic cells; some migrate throughout the body, whereas others reside permanently in organs and tissues where they are likely to encounter pathogens 3.) Dendritic cells: mainly populate tissues that contact the environment; they stimulate adaptive immunity against pathogens they encounter and engulf 4.) Eosinophils: often found beneath mucosal surfaces, have low phagocytic activity but are important in defending against multicellular invaders; upon encountering such parasites, they discharge destructive enzymes
antibodies and B cell receptors
Antibodies have the same Y-shaped organization as B cell antigen receptors, but they are secreted rather than membrane bound. It is the antibodies, rather than the B cells themselves, that actually help defend against pathogens. primary vs. secondary immune
Opsonization
Antibody opsonization is the process by which a pathogen is marked for ingestion and destruction by a phagocyte. Opsonization involves the binding of an opsonin, e.g., antibody, to a receptor on the pathogen's cell membrane.[1] After opsonin binds to the membrane, phagocytes are attracted to the pathogen
Explain how a single antigen can provoke a robust humoral response.
B cell activation leads to a robust humoral response: An activated B cell gives rise to a clone of thousands of plasma cells. Most antigens recognized by B cells contain multiple epitomes. An exposure to a single antigen normally activates a variety of B cells, with different clones of plasma cells directed against different epitomes on the common antigen.
Explain how B lymphocytes and T lymphocytes recognize specific antigens.
B cells and T cells use antigen-specific receptors embedded in their plasma membranes. The antigen receptors recognize epitopes, an accessible portion of an antigen.
Explain why the antigen receptors of lymphocytes are tested for self-reactivity during development.
Because antigen receptor genes are randomly rearranged, some immature lymphocytes produce receptors specific for epitopes on the organism's own molecules. if these self-reactive lymphocytes were not eliminate or inactivated, the immune system could not distinguish self from non-self and would attack body proteins, cells, and tissues.
Describe the functions of the proteins CD4 and CD8.
CD4 helps keep the helper T cell and antigen-presenting cell joined. CD8 helps keep the cytotoxic T cell and target cell joined.
Active Immunity
the immunity that results from the production of antibodies by the immune system in response to the presence of an antigen.
Compare the production and functions of class I MHC and class II MHC molecules.
Class I MHC molecueles bind to peptide fragments of foreign antigens synthesized within the cell and present antigens to cytotoxic T cells. Class II MHC molecules bind to antigen fragments derived from foreign materials that have been internalized through phagocytosis and present antigens to helper T cells.
Explain what is unique about the source of potential immune rejection in bone marrow grafts
Doctors will attempt to find a donor tissue bearing MHC molecules that match those of the recipient as closely as possible. Also, recipients take immunsuppressants afterwards to stop rejection. Bone marrow grafts are unique in that the graft itself, rather than the recipient, is the source of potential immune rejection. This is called a graft versus host reaction.
Briefly summarize the basic facts of acquired immunity.
Each B or T cell has many receptor proteins that can each bind a particular foreign molecule. After they're activated, they undergo cell division, creating some cells that kill infected host cells and others that secret proteins that attack foreign molecules in body fluids.
