Immune System
True or False: Most body cells have only class I MHC molecules, but antigen-presenting cells have both class I and class II MHC molecules. The class II molecules provide a molecular signature by which an antigen-presenting cell is recognized
True
True or False: After attaching to one or more microbes, a phagocyte engulfs the microbes, forming a vacuole that fuses with a lysosome.
True -- Make sure you understand that statement Hi Shoonki
Interferon
Two types of interferon proteins (called alpha and beta) provide innate immunity defense against viral infections. These proteins are secreted by virus-infected body cells and induce neighboring uninfected cells to produce other substances that inhibit viral reproduction. This can help contain the virus to a localized area A third type (gamma) can activate macrophages.
agranulocytes
WBCs that contain no visible cytoplasmic granules. Although they are found in the bloodstream, they are much more abundant in lymphoid tissue.
Fundamental Differences between T cell and B cell antigen receptors
Whereas the antigen receptors of B cells bind to epitopes of intact antigens circulating in body fluids, those of T cells bind only to fragments of antigens that are displayed, or presented, on the surface of host cells. The host protein that displays the antigen fragment on the cell surface is called an MHC (major histocompatibility complex) molecule.
granulocytes
White blood cells with irregularly shaped, multilobed nuclei and cytoplasmic granules. There are three types of granulocyte: neutrophils, eosinophils, and basophils. They are also known as polymorphonuclear leukocytes.
antigen processing and display in B cells
a B cell presents only the antigen to which it specifically binds. When an antigen first binds to receptors on the surface of a B cell, the cell takes in a few foreign molecules by receptor-mediated endocytosis. The class II MHC protein of the B cell then presents an antigen fragment to a helper T cell. This direct cell-to-cell contact is usually critical to B cell activation.
Gr8 animation
http://highered.mheducation.com/sites/0072495855/student_view0/chapter24/animation__the_immune_response.html
Structure of B cell Antigen Receptor (very important)
http://mcat-review.org/antibody.gif Remind me to find a better picture when you see this
This stuff can get confusing. These flashcards are mostly from the textbook. What is a website that you can use for review of immune system (and look at important diagrams too?)
http://mcat-review.org/circulatory-lymphatic-immune-systems.php#immune
memory cells
long-lived cells that can give rise to effector cells if the same antigen is encountered later in the animal's life.
effector cells
short-lived cells that take effect immediately against the antigen and any pathogens producing that antigen -The effector forms of B cells are plasma cells, which secrete antibodies. The effector forms of T cells are helper T cells and cytotoxic T cells
Cytokines
small proteins that direct the migration of phagocytes to injured tissue during the inflammatory response
cell-mediated immune response (in general terms)
specialized T cells destroy infected host cells
Lysozyme
-An important enzyme that digests the cell wall of many bacteria. -Present in saliva, tears, and mucous secretions, lysozymes can destroy many bacteria in saliva, near the eyes, or in the respiratory tract
Antigen & Antigen Receptor
-Any substance that elicits a response from a B cell or T cell is called an antigen. In adaptive immunity, recognition occurs when a B cell or T cell binds to an antigen, such as a bacterial or viral protein, via a protein called an antigen receptor. -An antigen receptor is specific enough to bind to just one part of one molecule from a particular pathogen, such as a species of bacteria or strain of virus. Although the cells of the immune system produce millions of different antigen receptors, all of the antigen receptors made by a single B or T cell are identical.
Phagocytes: Eosinophils
-Have low phagocytic activity, so are less important against most microbes -However, they are very important against scary multicellular parasites, like tapeworm or flukes
Phagocytes: Macrophages
-Large phagocyte that develop from moncytes, which are about 5% of circulating white blood cells -Carrying out phagocytosis sets off internal signaling mechanisms that increase the power of macrophages even more -Macrophages can also secrete a protein called "defensin" that damage pathogens without harming body cells.
Four types of white blood cells (leukocytes) are phagocytic. Name these four types
-Macrophages -Eosinophils -Neutrophils -Dendritic Cells acronym: MEND
Phagocytes: Neutrophils
-Neutrophils are the most abundant phagocytes. -They self-destruct during phagoyctosis, so they only last a few days
Nonspecifc Immunity (also called Innate Immunity) - know both terms
-Nonspecifc prevention of entrance of invaders into the body -Present before any exporsure to pathogens (hence, innate) -Effective from the time of birth -Essentially, a set of external barriers formed by the skin and mucous membranes coupled with a set of internal cellular and chemical defenses
Natural Killer (NK) Cells
-Patrol the body and tries to attack virus-infected body cells and cancer cells. It kills by apoptosis (programmed cell death). This is still part of innate immunity
lymph nodes
-Provide a site for WBCs (B cells) to reside and proliferate. -Removes pathogens from lymph. -Residing lymphocytes monitor lymph for foreign antigens, and initiate an immune response when exposed to foreign antigens.
spleen
-Provides a site for WBCs (B cells) to reside and proliferate. -Removes pathogens from blood. -Removes old RBCs and platelets.
Thymus and Bone Marrow
-Some lymphocytes migrate from the bone marrow to the thymus, an organ in the thoracic cavity above the heart. These lymphocytes mature into T cells. -Lymphocytes that remain and mature in the bone marrow develop as B cells. -Lymphocytes of a third type remain in the blood and become the natural killer cells active in innate immunity.
Phagocytes: Dendritic Cells
-They can also ingest microbes like macrophages, but their main role is actually in stimulating the development of acquired immunity
Explain the process/steps of inflammatory response (part of innate immunity)
1) Chemical signals (including Histamine) released by activated macrophages and mast cells at the injury site cause nearby capillaries to widen and become more permeable 2) Clotting elements, fluid, and antimicrobial proteins move from the blood to the site. (Clotting begins, and your skin turns red/bumpy) 3) Neutrophils and macrophages ingest pathogens and cell debris at the site, and the tissue heals
What are the two ways in which lysosomes can destroy microbes during phagocytosis?
1) toxic oxygen from lysosomes can poison microbes 2) lysozyme and other enzymes degrade microbes
Complement System
A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse pathogens. The complement system is activated in a cascade initiated by surface antigens on microorganisms or by antigen-antibody complexes. It is a part of innate immunity
antibody (immunoglobulin)
A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen; also called immunoglobulin. All antibodies have the same Y-shaped structure and in their monomer form consist of two identical heavy chains and two identical light chains.
Helper T cells
A type of T cell called a helper T cell triggers both the humoral and cell-mediated immune responses. Helper T cells themselves do not carry out those responses. Instead, signals from helper T cells initiate production of antibodies that neutralize pathogens and activate T cells that kill infected cells.
B cell activation leads to a robust humoral immune response
An activated B cell gives rise to thousands of identical plasma cells. These plasma cells stop expressing a membrane-bound antigen receptor and begin producing and secreting antibodies. An exposure to a single antigen therefore normally activates a variety of B cells, with different plasma cells producing antibodies directed against different epitopes on the common antigen.
Antibody Function
Antibodies do not kill pathogens, but by binding to antigens, they mark pathogens in various ways for inactivation or destruction. Types: neutralization: antibodies bind to viral surface proteins or toxins opsonization: antibodies bound to antigens on bacteria present a readily recognized structure for macrophages or neutrophils and therefore increase phagocytosis -can also work in conjunction with complement system
Activation of B cells
B cell activation by an antigen is aided by cytokines secreted from helper T cells that have encountered the same antigen. Stimulated by both an antigen and cytokines, the B cell proliferates and differentiates into memory B cells and antibody-secreting effector cells called "plasma cells"
What are the key players in Innate Immunity (Nonspecific Immunity)?
External Defense: Skin, Mucous Membranes, Secretions Internal Defense: Phagocytic Cells, Antimicrobial Proteins,, Inflammatory Response, Natural Killer Cells
Requirements for a helper T cell to activate adaptive immune responses
First, a foreign molecule must be present that can bind specifically to the antigen receptor of the T cell. Second, this antigen must be displayed on the surface of an antigen-presenting cell. The antigen presenting cell can be a dendritic cell, macrophage, or B cell.
Antigen Recognition by T-Cell's (refer to bottom of page 936 of Campbell's Biology)
For a T cell, the antigen receptor consists of two different polypeptide chains, an a chain and a b chain, linked by a disulfide bridge. Near the base of the T cell antigen receptor (often called simply a T cell receptor) is a transmembrane region that anchors the molecule in the cell's plasma membrane. At the outer tip of the molecule, the variable (V) regions of α and β chains together form a single antigen-binding site. The remainder of the molecule is made up of the constant (C) regions.
Septic Shock
High fever and low blood pressure can cause sickness or death in "septic shock", which is a huge inflammatory response that overwhelms the body
Histamine & Mast Cells
Histamine is an important chemical signal that is stored in mast cells found in connective tissues. When mast cells are injured, they increase the size of capillaries around them (part of the inflammatory response).
Phagoytosis's role in innate immunity?
If a bacteria gets into the body, phagocytosis can occur. Phagoytosis is the ingestion of invading microorganisms by certain types of white blood cells generically referred to as "phagocytes"
secondary immune response
If an individual is exposed again to the same antigen, the response is faster (typically peaking only 2-7 days after exposure), of greater magnitude, and more prolonged. This is the secondary immune response, a hallmark of adaptive, or acquired, immunity
humoral immune response
In the humoral response, antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph.
Immune Response summary of animation
Pathogen activates immune response. Macrophages ingest pathogens and process to display antigens on surface (called antigen presenting cell). Interacts with T helper cells. Macrophage releases Interleukin 1 to T cells, which secrete Interleukin 2 --> causes proliferation of cytotoxic T cells or B cells. Cytotoxic T cells: recognize particular antigens, even on normal cells that got infected. T cells kill infected cells. B Cells: recognize specific antigens. Activated by helper T cells. Differentiate into plasma cells, which produce antibodies. The released antibodies bind to pathogens, marking them for destruction by macrophages. Some B cells become memory cells (which can live for decades). This makes the secondary immune response swifter and stronger. Creates immunity in ppl after one time or vaccination.
Oil Glands and Sweat Glands Function in Innate Immunity
Secretions from Oil Glands and Sweat Glands are acidic, which is too acidic for many microbes. (Similar function to that the acid in stomach has against microbes)
self-tolerance
Since the body normally lacks mature lymphocytes that can react against its own components, the immune system is said to exhibit self-tolerance
lymphocytes
The adaptive response relies on T cells and B cells, which are types of white blood cells called lymphocytes
antigen presentation
The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell.
primary immune response
The production of effector cells from a clone of lymphocytes during the first exposure to an antigen is the basis for the primary immune response
Epitope
The small, accessible portion of an antigen that binds to an antigen receptor is called an epitope, or antigenic determinant. An example is a group of amino acids in a particular protein. 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 cell 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.
Cytotoxic T cells
The targeted destruction of an infected host cell by a cytotoxic T cell involves the secretion of proteins that disrupt membrane integrity and trigger apoptosis. To become active, they require signaling molecules from helper T cells as well as interaction with a cell that presents an antigen
