Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
46 Cards in this Set
- Front
- Back
|
Why do we have an immune system?
|
-Distinguish self from non self
-Prevents infection -Eradicates established infections -Significance is demonstrated by immunosuppressed people develop life threatening infections and stimulating immune responses protects against infections (vaccinations) |
|
|
What is innate immunity?
|
-Mediates intial protection against infections
-Present from birth and for life -No specificity -No memory -Innate response most useful in the protection against; pyogenic organisms, fungi, multicellular parasites -May be sufficient to prevent disease otherwise adaptive immune response is activated |
|
|
What are the physical/chemical barriers in the innate immune system?
|
-Mucus, cilia, acid in stomach, skin, flushing of urinary tract
|
|
|
What cells are involved in innate immune response?
|
-Macrophages (professional phagocyte)
-Neutrophils (professional phagocytes) -Dentritic cells -Eosinophils -Mast cells -NK cells -Macrophages and neutrophils release cytokines which signal between lymphocytes and phagocytes and other cells |
|
|
What are the characteristics of monocytes/macrophages?
|
-Made in bone marrow from stem cells
-Monocytes in blood and circulate for ~24hrs -Macrophages are in tissues and are placed to filter off foreign material -Long lived cells; mitochondria -Generally first phagocytic cell to sense an invading microbe -Provide a warning to other cells orchestrate the local response to infection by recruiting neutrophils and other leukocytes to the area -The major cell in chronic inflammation -Combat microbes that llive in host cells |
|
|
What are the characteristics of neutrophils?
|
-70% of WCC in blood
-Involved in killing pyogenic bacteria and fungi -Receptors for chemotactic factors released by microbes and complement -Non dividing short lived cells (4-5days) -No mitochondria, rely on glycogen stores and can function under anaerobic -Release granule contents; myeloperoxidase, lysozyme, acid hydrolases -Circulate in the blood in search of invading microbes but also recruited to sites of infection or inflammation -Major cells of acute inflammation |
|
|
What features of microbial structure do innate immune cells distinguish?
|
-Pattern recognition receptors (PRR) recognise pathogen associated molecular patterns (PAMPS) associated with certain kinds of microbes
-Facilitates the removal of microbes similar structures |
|
|
What occurs after PRR recognise PAMPS?
|
At the onset of an infection, burn, or other injuries, these cells undergo activation (one of their PRR recognize a PAMP) and release inflammatory mediators responsible for the clinical signs of inflammation.
Chemical factors produced during inflammation (histamine, bradykinin, serotonin, leukotrienes also prostaglandins) sensitize pain receptors, cause vasodilation of the blood vessels at the scene, and attract phagocytes, especially neutrophils.[5] Neutrophils then trigger other parts of the immune system by releasing factors that summon other leukocytes and lymphocytes. Cytokines produced by macrophages and other cells of the innate immune system mediate the inflammatory response. These cytokines include TNF, HMGB1, and IL-1. |
|
|
What is the process of phagocytosis?
|
-Surface receptors (PRP's) first recognise and bind to common constituents of bacterial surfaces (PAMPS)
-Signals actin myosin contractile system -Cytoplasmic lysosome granules fuse with phagosome to form phagolysosome -Contents are discharged and microbes are killed and then digested by enzymes |
|
|
What is the role of dendritic cells?
|
-Present in tissues that are in contact with the external environment and in the blood in the immature form
-Share many properties with macrophages but their function is not to clear the pathogen -Role is as inteface between innate and adaptive immunity |
|
|
How do dendritic cells interface between innate and adaptive immunity?
|
-recognise microbial antigens through innate receptors
-Act as cellular messenger to call up an adaptive immune response when required -Leave infected tissue with cargo of intact/degraded pathogens to lymphoid organs that specialise in making the adaptive immune response here they present the antigen to T cells |
|
|
What are the characteristics of eosinophils?
|
-3-5% of circulating granulocytes
-Have some phaocytic activity -Large pathogens (eg helminths) cannot be engulfed by phagocytes -release granule contents (basic proteins) to kill these pathogens -Play role in allergic disease via release of histamine. |
|
|
What are the characteristics of basophils and mast cells?
|
-Basophils <0.2% of circulating leukocytes and have structural and functional similarities to mast cells
-Mast cells are resident in mucosal and epithelial tissues |
|
|
What stimulates the release of granules from basophils and mast cells?
|
-Binding to complement factors C3A an C5A
-When allergens cross link IgE molecules on surface (ie specific immunity) -Binding to lectins (sugar binding molecules) |
|
|
What are contained in granules of basophils and mast cells?
|
-Histamins and heparin
-Cause adverse symptoms of an allergy -Play a role in immunity against parasites by enhancing acute inflammation; attracting neutrophils and eosinophils |
|
|
What are the characteristics of Natural Killer Cells?
|
-Large granular lymphocytes
-Non B and non T cells -5-15% of lymphocyte fraction -Fc and IgG receptors -Kill tumour cells and virally infected cells -Release granule contents (eg perforin) extracellularly which inserts into the membrane of the target cell -Enables the entry of other granule proteins to kill the cell by apoptosis |
|
|
What is the complement system?
|
It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime. However, it can be recruited and brought into action by the adaptive immune system.
The complement system consists of a number of small proteins found in the blood, generally synthesized by the liver, and normally circulating as inactive precursors (pro-proteins). When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages. The end-result of this activation cascade is massive amplification of the response and activation of the cell-killing membrane attack complex. Over 25 proteins and protein fragments make up the complement system, including serum proteins, serosal proteins, and cell membrane receptors. |
|
|
What is the function of the complement system?
|
-Initiate acute inflammation by direct activation of mast cells (C3a, C5a)
-Chemotaxis; attraction of neutrophils (C5a) -Opsinisation; enhancement of attachment of the microbe to the phagocyte (C3b) -Killing of the microbe by activating the membrane attack complex (C9) |
|
|
What is opsonins?
|
An opsonin is any molecule that targets an antigen for an immune response. However, the term is usually used in reference to molecules that act as a binding enhancer for the process of phagocytosis, especially antibodies, which coat the negatively-charged molecules on the membrane. Molecules that activate the complement system are also considered opsonins. Phagocytic cells do not have an FC receptor for IgM, making IgM ineffective in assisting phagocytosis. However, IgM is extremely efficient at activating complement and is, therefore, considered an opsonin. Opsonins can also refer to molecules that target a cell for destruction through the action of natural killer (NK) cells.
|
|
|
What are acute phase proteins?
|
Acute-phase proteins are a class of proteins whose plasma concentrations increase (positive acute-phase proteins) or decrease (negative acute-phase proteins) in response to inflammation. This response is called the acute-phase reaction (also called acute-phase response).
Inflammatory cells and red blood cells In response to injury, local inflammatory cells (neutrophil granulocytes and macrophages) secrete a number of cytokines into the bloodstream, most notable of which are the interleukins IL-1, IL-6 and IL-8, and TNF-α. The liver responds by producing a large number of acute-phase reactants. At the same time, the production of a number of other proteins is reduced; these are, therefore, referred to as "negative" acute-phase reactants. As such, increased acute phase proteins from the liver may also contribute to the promotion of sepsis. |
|
|
What are the functions of acute phase proteins?
|
-Bind components to the bacterial wall
-Maximise activation of the complement system -Opsonisation of microbes for phagocytosis -Some inhibit microbial growth or limit tissue damage by neutralising lysosomal enzymes released from phagocytes. |
|
|
What is the role of cytokines in the innate immune system?
|
-Small cells secreted by cells in response to a stimulus
-Signaling between cells -Induce growth, differentiation, chemotaxis, activation and enhanced cytotoxicity -Same cytokine can be produced by different cell populations or can induce different functions in different cell types |
|
|
What are some examples of cytokines produced?
|
-Monokines; secreted by myeloid cells
-Lymphokines; secreted by lymphocytes -Interleukins; cytokines produced by leukocytes -Chemokines; heparin binding molecule that direct cell migration -Interferons; produced by a number of cells in response to viral infection |
|
|
What is fibronectin?
|
-Protein of the innate immune system that bind bacteria and is recognised by phagocytosis
|
|
|
What is Lysozyme?
|
-Protein of the innate immune system
-Bactericidal enzyyme in body fluids and neutrophil granules -Splits the proteoglycan cell wall of bacteria |
|
|
What is lactoferrin?
|
-Protein of the innate immune system
-Appears in the blood and can complex iron to deprive bacteria of this growth factor |
|
|
What are some examples of cytokines produced?
|
-Monokines; secreted by myeloid cells
-Lymphokines; secreted by lymphocytes -Interleukins; cytokines produced by leukocytes -Chemokines; heparin binding molecule that direct cell migration -Interferons; produced by a number of cells in response to viral infection |
|
|
Define adaptive immunity
|
-Act against microorganisms that overcome the innate defences
-Has specificity for each particular organism -Has memory and therefore a more effective response occurs on the 2nd and subsequent encounters with the particular antigen |
|
|
What is fibronectin?
|
-Protein of the innate immune system that bind bacteria and is recognised by phagocytosis
|
|
|
What are the components of the adaptive immune system?
|
-Cellular; B and T lymphocytes
-Secreted products; antibodies, lymphokines, interleukins, interferon |
|
|
What is Lysozyme?
|
-Protein of the innate immune system
-Bactericidal enzyyme in body fluids and neutrophil granules -Splits the proteoglycan cell wall of bacteria |
|
|
What does the adaptive immunity protect from?
|
Bacteria, including intracellular infection
Viruses Protozoa |
|
|
What is lactoferrin?
|
-Protein of the innate immune system
-Appears in the blood and can complex iron to deprive bacteria of this growth factor |
|
|
What are lymphocytes?
|
-Produced in bone marrow
-Total 10^12 lymphoid cells int he body -10^9 produced eacch day -Comprised 25-35% of white blood cells -Unlike other blood cells they recirculate around the body (blood-tissue-blood) -Each lymphocyte is genetically programmed such that it has individual receptors to recognise one particular antigen (specific) -Undergo clonal proliferation when they are activated by their receptor making contact with its specific antigen -Show memory to give rise to a faster and bigger immune response on rechallenge -B and T cells |
|
|
Define adaptive immunity
|
-Act against microorganisms that overcome the innate defences
-Has specificity for each particular organism -Has memory and therefore a more effective response occurs on the 2nd and subsequent encounters with the particular antigen |
|
|
What are the characteristics of B lymphocytes?
|
-Present antigen
-have immunoglobulins (antibodies) on their surface which act as antigen receptors -When stimulated through their antigen receptor they deveplop into antibody secreting plasma cells and secrete one antibody type |
|
|
What are the components of the adaptive immune system?
|
-Cellular; B and T lymphocytes
-Secreted products; antibodies, lymphokines, interleukins, interferon |
|
|
What are the characteristics of T lymphocytes?
|
-Finish maturation in the thymus
-Respond by clonal proliferation -Have either CD4 or CD8 T cell receptors on their surface -Recognise an infected cell as a target by binding to surface major histocompatability complex (MHC) class I or II |
|
|
What does the adaptive immunity protect from?
|
Bacteria, including intracellular infection
Viruses Protozoa |
|
|
What are lymphocytes?
|
-Produced in bone marrow
-Total 10^12 lymphoid cells int he body -10^9 produced eacch day -Comprised 25-35% of white blood cells -Unlike other blood cells they recirculate around the body (blood-tissue-blood) -Each lymphocyte is genetically programmed such that it has individual receptors to recognise one particular antigen (specific) -Undergo clonal proliferation when they are activated by their receptor making contact with its specific antigen -Show memory to give rise to a faster and bigger immune response on rechallenge -B and T cells |
|
|
What are the characteristics of B lymphocytes?
|
-Present antigen
-have immunoglobulins (antibodies) on their surface which act as antigen receptors -When stimulated through their antigen receptor they deveplop into antibody secreting plasma cells and secrete one antibody type |
|
|
What are the characteristics of T lymphocytes?
|
-Finish maturation in the thymus
-Respond by clonal proliferation -Have either CD4 or CD8 T cell receptors on their surface -Recognise an infected cell as a target by binding to surface major histocompatability complex (MHC) class I or II |
|
|
What are the functions of T cells?
|
-Help or amplify the response mainly by cytokine production
-Release macrophage activating factors to help macrophage kill the intracellular microbe -Help B cells make antibodies -Kills cells bearing the stimulating antigen |
|
|
What is the role of tissue in immune reactions?
|
-To generate an immune response, antigen must react with a number of different cells, which also must interact with each other
-Cells are organised into tissues and organs so these interactions can occur; lymphoid system -Classified into primary lymphoid organ and secondary lymphoid organ -Primary; major site of proliferation and differentiation of lymphocytes (bone marrow and thymus) -Secondary; create the environment in which the lymphocytes interact with one another and with the antigen (disseminate effector cells and molecules) -Lymphocytes circulate via the blood and lymphatics to other secondary lymphoid tissue |
|
|
Where are antigens delievered to?
|
-Tissue infection; antigen is trapped by macrophages and dendritic cells and carries to the lymphatics to the draining lymph nodes
-Microbes on mucosal surfaces are taken up by specialised M cells and delivered to mucosal associated lymphoid tissue -Blood born antigens are trapped in the spleen, phagocytosed by macrophages and dendritic cells present |
|
|
How does delivery of antigen and lymphocyte traffficking occur?
|
-Passage of lymphocytes through an area where antigen is localised facilitates induction of the immune reponse
-Lymphocytes with the appropriate receptors bind antigen and become activated -Activated lymphocytes mature into effector cells -B cells become plasma cells in lymphoid tissue and produce antibody (B cells can also recirculate) -Tcells leave secondary lymphoid tissue and return to site of infection to help detroy infectious agent |
