Ch 15 Innate and Adaptive Immunity Flashcards
What are the two host defenses? What are the differences?
Innate and Adaptive immunity.
Innate is the early, rapid responses consist of the physical, chemical, molecular and cellular defenses that are in place before infection and can function immediately as an effective barrier to microbes. They are the skin and mucous membranes, phagocytic leukocytes, specialized lymphocytes and several plasma proteins
Adaptive is the second defense, responding less rapidly but more effectively. Uses focused recognition of each unique type of foreign agent followed by an amplified and effective response Consists of two groups of lymphocytes and their products, Antibodies, antigens Humoral is antibodies that are produced by b cells and cell mediated immunity is t cells
What are the cells of the immune system? What do they do?
Myeloid lineage phagocytic cells - part of the innate immune system 3 types
- Monocytes/macrophages - are in all tissues, are fairly long lived cells and several functions - phagocytosis of invading microorganisms, they also functions as antigen presenting cells of the adaptive response.
- Granulocytes - three types neutrophils, eosinophils, and basophils - relatively short lived, in inc numbers. They take up a variety of microorganisms in phagocytosis and efficiently destroy them using degradative enzymes and other antimicrobial substances.
- Dendritic Cells - long fingerlike processes and are found in tissue and in most organs- they are antigen presenting cells that initiate adaptive immune responses
Lymphocytes and natural killer cells
B cells are the only cells capable of producing antibodies, They are used to recognize a wide variety of proteins, polysaccharides, lipids, and small chemicals. The secreted antibodies enter the circulation and mucosal fluids and bind to microbes before they have a chance to colonize body tissues.
T cells they help b cells produce antibodies and help phagocytic cells destroy t cells that kill or lyse intracellular microbes.
What are the organs and Tissues of the Immune System?
- Central Lymphoid Tissues, the bone marrow, and thymus gland. Provide the environment for immune cell production and maturation. T cells made in the bone marrow move along the lymph system to the thymus to mature only the ones that recognize foreign antigens and self are able to leave. The b cell mature in the bone marrow and acquire immunoglobulin Ig signaling molecules and cells markers
Peripheral lymphoid tissues are the lymph nodes, spleen and other secondary lymphoid tissues,
Lymph nodes are highly organized lymphoid organs with two functions 1. they filter foreign material from lymph before it moves to the blood stream. Located at points of convergence of lymphatic vessels 2. they serve as centers for proliferation and response of immune cells. Small bean shaped encapsulated organ
Spleen is a large ovoid secondary organ located high in the left abd It filters antigens from the blood and is important in the response to systemic infections. Composed of white and red pulp.
Other secondary lymphoid tissue - mucosa associated lymphoid tissues MALT. These nonencapsulated clusters of lymphoid tissues are located around membranes lining the respiratory, digestive, and urogenital tracts. In some they congregate in loose clusters but in other like the tonsils, peyer patches in the intestine, the appendix organized structures are evident.
What are cytokines? What are chemokines? What are colony stimulating factors?
Cytokines are low molecular weight regulatory proteins that are produced by cells of the innate and adaptive immune systems and that mediate many of the actions of these cells. Most released at cell to cell interfaces, where they bind to specific receptors on the membrane surface of their target cells. All are secreted in a brief, self limited manner. Are usually not stored as performed molecules and their synthesis is limited. The actions are often pleiotropic and redundant
Chemokines are cytokines that stimulate the migration and activation of immune and inflammatory cells. They are implicated in a number of acute and chronic diseases, including atherosclerosis, RA, IBS allergic asthma, chronic bronchitis, MS, lupus and HIV
CSF are cytokines that stimulate bone marrow pluripotent stem and progenitor cells to produce large number of platelets, erthrocytes, lymphocytes, neutrophils, monocytes, eosinophils, basophils, and dendritic cells. Named according to the type of target cell on which they act.
What is Innate Immunity and what are different systems do?
- Epithelial barriers, provide physical and chemical barriers between the internal and external pathogens. The skin also has salty acidic environment and antibacterial proteins. Mucous membranes are protected by sheets of tightly packed epithelial cells, that secrete a viscous material mucus. Might have cilia to help move the microbes away. Once trapped lysozyme and hydrolytic enzyme cleave the bacterial walls
Cells of innate immunity - phagocytic leukocytes recognize and kill infectious agents which is programmed with general groups of microbes. Neutrophils first appear and start then macrophages who are more specific come, they are activated to engulf and digest microbes that attach to their cell membrane. Once done the cell generates digestive enzymes and toxic peroxide or nitric oxide that kill the pathogen. Dendritic cells It can govern early response to viral infections. NK cells are lymphocytes that recognize infected and stressed cells and respond by killing these cells. It triggers the release of cytoplasmic granules toward the infected cells. The molecules form pores in the cell membrane and other molecules that induce apoptosis. They control their responses by using both activating and inhibitory receptors.
What is pathogen recognition? Pattern recognition and toll like receptors?
These receptors are molecules that first tag the microbe and then bind it to the effector cell of the innate immune system.
- Pattern recognition - microbes typically bear repeating patterns of molecular structure on their surface. Cell walls of gram negative and positive bacteria are composed of a matrix of sugars, lipid molecules, proteins or patterns of modified nucleic acids. PAMP pathogen associated molecular patterns and PRR pattern recognition receptors PAMP are essential to the functioning and infectivity of the microbe. Like macrophage- mannose receptor recognizes certain sugars found on the surface of many bacteria and viruses, including HIV.
- Toll like receptors - they can recognize elements of most microorganisms but there are only 11 we know so far. Ligand binding to the TLR at the cell surface lease to an intracellular cascade of events which ultimately regulates the production of several proteins that are important components of the innate immunity.
What is the complement system? What are the three phases?
Three parallel but independent pathways.
- Classical pathway - recognizes complement fixing antibodies IgG, IgM of adaptive immunity bound to the surface of a microbe or other structure.
- Lectin pathway - uses a plasma protein the mannose binding ligand that binds to mannose residues on microbial glycoproteins or glycolipids.
- Alternative pathway - which recognizes certain microbial molecules in the absence of antibody.
- initial activation, 2. amplification of inflammation 3. membrane attack response. All act on the complement protein C3 All generate a series of enzymatic reactions that prompt enzymatic cleavage of C3 into two fragments. C3a triggers an influx of neutrophils to enhance the inflammatory response, production of C3a and C5a also leads to the activation of basophils and mast cells and the release of inflammatory mediators that produce smooth muscle contraction, inc vascular permeability and changes in endothelial cells to enhance migration of phagocytes.
What is adaptive immunity and the role of antigens?
Antigens are foreign substances that elicit specific responses and stimulate an immune response. They are recognized by receptors on immune cells and by secreted proteins called antibodies which are made in response to the antigens. Antigens include bacteria, fungi, viruses, protozoa, and parasites as well as nonmicrobial agents like plant pollens. They are in general large and chemically complex, are biologically degraded into smaller chemical units or peptides.
What are the cells and molecules of adaptive immunity? What are antigen presenting cells? Lymphocytes? Major Histocompatibility complex molecules?
B and T cells are the effector cells that specifically recognize and respond to foreign antigens.
Antigen presenting cells - Macrophages - the general scavenger cells of the body. Dendritic cells - in most tissues where antigen enters the body and in the peripheral lymphoid tissues. Langerhans are specialized dendritic cells in the skin
Lymphocytes - b and t lymphocytes they can specificity, diversity, memory and self non self recognition. Divide several times to form clonal cell populations that differentiate into effector or memory cells. T cell differentiate into helper of cytotoxic t cells.
Major histocompatibility - are membrane bound proteins encoded by a MHC gene locus that display peptides for recognition by t cells. They are critical to the induction of tcell immunity. as they can reject transplant organs are human MHC proteins called human leukocyte antigens HLA
What are b lymphocytes and humoral immunity? What are immunoglobulins?
The mature b cell leaves the bone marrow and migrates to the various peripheral lymphoid tissues, where it is stimulated to respond to a specific antigens They the antigen and receive t cell help undergo a series of changes that transform them into antibody-secreting plasma cells or into memory B cells.
Immunoglobulins function as antigen receptors for B cells and are divided into 5 classes IgG, IgA, IgM, IgD and IgE - each with a different role.
IgG - most abundant, is present in body fluids and readily enters the tissues (only one to cross the placenta and offer immunity to the fetus) it protects against bacteria, toxins and viruses in body fluids and activates the complement system. can bind to target cells and receptros on NK cells and macrophages leading to lysis of the target cell.
IgA - secretory is found in saliva, tears, breast milk and bronchial, gi, prostatic, vaginal secretions. Is considered the primary defense against local infections in mucosal tissues.
IgM - is a macromolecule that forms a polymer of 5 basic immunoglobulin units. It the first to appear in response to an antigen and is the first antibody type made by the newborn.
IgD - is found primarily on the cell membranes of b cells and is used for differentiation of b cells.
IgE - is involved in inflammation, allergic responses, and combating parasitic infections. Binds to mast cells and basophils. which triggers histamine release
Humoral immunity - functions to eliminate extracellular microbes and microbial toxins. two types
Primary - occurs when the antigen is first introduced into the body. activates CD4 helper t cells trigger b cells to proliferate and differentiate into a clone of plasma cells that produce antibody. takes 1-2 weeks Vaccination.
secondary - occurs on second exposure to the antigen. memory b cells. In the secondary response the rise in antibody occurs sooner and reaches a higher level. Used in immunization like tetanus. Booster
What are t cells and cell mediated immunity? What are helper t cells? Cytotoxic t cells? Regulatory t cells? Cell mediated immunity?
They control the intracellular viral infections, in the rejection of foreign tissue grafts and in delayed hypersensitivity reactions.
Helper t cells - serves as the master regulator of the immune system. Once activated they secrete cytokines that influence the function of nearly all other cells of the immune system.
Cytotoxic t cells - Activated by CD8 lymphocytes become cytotoxic t cells after recognition of class I MHF antigen complexes on target cell surfaces, The recognition of antigen complexes on infected target cells ensures that neighboring uninfected host cells , which express class I MHC molecules alone or with self peptide, are not indiscriminately destroyed.
Regulatory t cells - has CD4 and CD25 expressed on its cell membrane. They suppress immune responses by inhibiting the proliferation of other potentially harmful self reactive lymphocytes.
Cell mediated immunity - functions against microbes, including bacteria, parasites, and all viruses that replicate inside cells where they cant be destroyed by antibodies. CD8 and CD4 contribute to the response, with each having different effector mechanisms for the eradication of the infection
