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immunology Flashcards

1
Q

what is the lymphatic system comprised of

A

-lymphatic vessels
-lymph
-lymphoid [immune] cells, tissues and organs

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2
Q

what are the functions of the lymphatic system

A

captures lost fluid from blood
transports dietary lipids
transports foreign substances and immune cells from tissues to lymphoid organs

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3
Q

where does lymphatic drainage empty

A

into venous system [right lymphatic duct and thoracic duct]

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4
Q

what is lymph

A

captured lost fluid [IF] and transports it back to the blood

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5
Q

what are the innate system defences

A

-surface barriers [skin and mucous membranes]
-internal defences [phagocytes, NK cells, inflammation, antimicrobial proteins and fever]

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6
Q

what are the adaptive immune system defences

A

-humoral immunity [B cells]
-cellular immunity [T cells]
[both lymphocytes]

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7
Q

what are the cells of the immune system

A

-neutrophils
-eosinophils
-basophils/mast cells
-macrophages
-dendritic cells
-NK cells
-lymphocytes [B/T cells]

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8
Q

Neutrophils

A

-aka polymorphonuclear neutrophils [PMNs]
-most abundant phagocyte [up to 70% of WBCs]
-first cell to arrive at site of infection
-chemotactic [attracted by chemical gradients]
-major defence against bacterial infection
-generate ROS vis ‘respiratory burst’

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9
Q

eosinophils

A

-granulocyte
-contains granules packed with digestive enzymes
-key role in defence against parasitic worms

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10
Q

basophils

A

-granulocyte
-granules contain histamine and heparin
-major role in inflammation together with mast cells

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11
Q
A
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12
Q

macrophages

A

-large agranular cells derived from monocytes that have entered tissue
-actively phagocytic [engulf foreign particles]
-deploy weapons [lysozymes, ROS]
-component of innate but play large role in adaptive [involved in activation of lymphocytes, present antigens]

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13
Q

Dendritic cells

A

-located in epithelia and most organs with characteristic long ‘arms’
-migrate to lymphatic system once antigen is internalised
-present antigen to T cells in lymph nodes
-major link between innate and adaptive

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14
Q

NK cells

A

-cytotoxic against some cancer cells and virally-infected cells
-lack specific antigen receptors [recognise defected self antigens [MHC]
-release perforins and granzymes [innate cell destruction by apoptosis]

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15
Q

lymphocytes of adaptive immune system

A

-mature in primary lymphoid organs [bone marrow or thymus]
-migrate between secondary lymphoid tissues
-able to recognise specific antigens

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16
Q

B cells

A

-possess cell surface receptors [immunoglobulin bound to surface] [specific for only one type of antigens, produce antibody immunoglobulin]
-differentiate in plasma cells producing large amounts of antibodies

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17
Q

T cells

A

-each cell expresses a unique antigen specific receptor
-perform both effector and regulatory roles
-helper t-cells [antigen specific t cell receptor, co-receptor molecule CD4]
-cytotoxic t cells [antigen specific, co-receptor molecule CD8]

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18
Q

primary lymphoid organs

A

bone marrow and thymus
[sites at which lymphocytes mature and develop antigen specificity]

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19
Q

secondary lymphoid organs

A

lymph nodes, spleen, mucosa-associated lymphoid tissue [MALT]
[site at which lymphocytes are activated when they recognise their specific antigen]

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20
Q

thymus

A

-site of T-cell maturation [immunocompetence]
-highly active after birth
-atrophies after puberty [involution]
-remains active but rate declines with age

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21
Q

lymph nodes

A

-bulbous kidney shaped organs up to 25mm in diameter
-large collections of nodes present throughout body [cervical, axillary and inguinal regions, around 600 in total]
-perform two major functions [filtration, immune activation]

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22
Q

spleen regions

A

-2 distinct regions
-red pulp [contains vascular sinuses filled with RBCs and macrophages
-white pulp [contains lymphocytes on reticular fibres

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23
Q

what are the spleen functions

A

-cleanses blood [removes old and defective blood cells and platelets, resident macrophages remove foreign particles and debris]
-recycles breakdown products [inro from RBCs stored for use in making haemoglobin]
-stored monocytes and platelets

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24
Q

mucosa-associated lymphoid tissue [MALT]

A

-lymphoid tissue found in mucous membranes in different parts of body
-tonsils [palatine, lingual, pharyngeal]
-peyer’s patches [wall of small intestine]
-appendix

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25
innate system -skin layers
-epidermis [renewable mechanical barrier] -dermis/hypodermis [contains sweat glands, sebaceous glands] -secretion of various anti bacterial chemicals
26
innate system -mucous membrane
-goblet cells secrete mucus -various anti bacterial chemicals -first point of contact with pathogens from external environment
27
commensal bacteria
-normal microbiota may inhibit pathogen colonisation in several ways -formation of bacterial layer [prevents more pathogenic bacteria from forming large colonies] -compete for nutrients and space -production of bactericides [inhibit other bacteria]
28
inflammation
-causes pain, redness, heat and swelling -attempt to rid area of pathogens and accelerate recovery
29
what are the three stages of inflammation
-vasodilation and increased permeability of blood vessels -accumulation of phagocytes and antimicrobial proteins in area -clearance of pathogens and accelerated tissue repair
30
mobilising phagocytes
-leukocytosis -margination -diapedesis -chemotaxis
31
what is leukocytosis
injured cells releases factors that increase the number of circulating WBCs
32
what is margination
Expression of cell adhesion molecules (CAMs) that enables phagocytes to adhere to capillary walls
33
what is diapedesis
Phagocytes pass through capillary wall into injured tissues
34
what are chemotaxis
Cells are attracted to site of injury along chemical gradients
35
chemical mediators of acute inflammation
-proteins/enzyme cascades [kinins and complement proteins] -lipid-derived mediators [prostaglandins and leukotrienes] -vasoactive amines [histamine released by mast cells/basophils] -cytokines [signalling proteins involved in communication and control of immune repsonses]
36
antimicrobial proteins
-collection of cellular and plasma proteins that enhance immunity -includes -interferons -complement -other antimicrobials
37
what are interferons
-antiviral proteins produced by virally infected cells -able to protect neighbouring cells -some also exert control over inflammation and activate NK cells and macrophages
38
what are complement antimicrobial proteins
-collection of over 20 plasma proteins -normally present in an inactive state -when activated, enhance inflammation and phagocytosis and directly kill bacteria major mechanism for destroying pathogens -contributes to both innate and adaptive immune responses
39
complement activation
-classical pathway [initiated by binding of antibody to antigen and activation of C1] -Mannose-binding lectin [MBL] [activated by lectin binding to mannose of micro-org surface] -alternative pathway [initiated by activation of C3 and factors B,D,P through interaction with microbe surface]
40
complement functions
-C3a enhances inflammation [reduces release of other chemical signals] -C3b promotes phagocytosis through opsonisation [coats microbe with C3b molecules, promotes uptake of microbe by phagocytes] -C5a enhances inflammation -C5b forms membrane attack complex with C6,7,8,9
41
other antimicrobial proteins
-lysozyme [present in some body fluids and phagocytic granules [enzymatically degrades peptidogylcan in bacterial cell walls]] -various peptides including defensins and cathelicidins [disrupt microbial membranes, inhibit nucleic acid or protein synth in numerous bacteria, viruses and fungi]
42
divisions of adaptive immunity
-humoral -cellular
43
humoral immunity
-antibody-mediated -immune function performed by release of immunoglobulin [antibodies] -blocks entry of pathogen or target pathogen for destruction
44
cellular immunity
-cell-mediated immunity -immune function performed by cells -causes death of infected cells and pathogens within them
45
antigen specificity meaning
antigen-toxin or foreign substance which induces an immune response specificity-ability to bind one but not another member of a family of related substances
46
antigens - clonal selection theory
-proposed by McFarlane Burnett to explain diversity in antibodies -name derived from antibody generator [antigen]
47
response of antigen binding to receptor
-activation of B cells [release of immunoglobulin] -activation of T cells [killing of infected cells/release of cytokines]
48
where can antigens be found
foreign organisms or particles such as -bacteria -viruses -toxins -foreign tissue [transplant organs etc] also found on our own cells [posses their own self antigens, e.g. A,B,Rh antigens on RBCs]
49
immunocompetence
- Lymphocytes must be able to recognise and respond a large number of foreign antigens -Must not respond to normal self antigens (self tolerance)
50
lymphocyte development
-lymphocytes develop immunocompetence in primary lymphoid organs -b cells mature in bone marrow -t cells in thymus -mature lymphocytes circulate between secondary lymphoid organs where they encounter antigen
51
human self-antigen
major histocompatibility complex [MCH] moles [key molecules to match in organ transplantation]
52
role of MHC molecules
-incorporate and present antigens to T cells [forms antigen/MHC complex, antigen presented as a peptide sequence, recognised by T cell receptor]
53
types of MHC molecules
class 1 [displayed by all nucleated cells, incorporate foreign peptides generated within cell, present peptide-MHC 1 to CD8+ Tcells] class 2 [displayed by professional antigen presenting cells, engulf and break down antigens into peptide, present peptide-MHC 2 to CD4+ Tcells]
54
antigen presenting cells
-professional APC include dendritic cells, macrophages, and B cells -engulf and destroy foreign pathogens [phagocytosis] -package foreign peptide sequence onto MCH2 molecules -display or present antigen-MHC 2 complex to CD4+ T cells
55
b cell activation process
-antigen binds to B cell receptor [immunoglobulin on cell surface] -activation [via helper CD4+ T cell] -proliferation [division] and differentiation
56
B cell activation -proliferation and differentiation
-divide into many daughter cells [proliferation] -differentiate to produce 2 distinct cell types -plasma cells [secrete large quantities of immunoglobulin] -memory B cells [tailored antibody response to pathogen]
57
antibody IgM
-first class secreted by plasma cells during primary response -readily fixes and activated complement -exists in monomer/pentamer forms -serves as an antigen receptor on B cell surface -numerous antigen binding sites make it a potent agglutinating agent
58
antibody IgA
-dimer, secretory IgA found in body secretions [saliva, sweat, intestinal juice and milk] -helps stop pathogens from attaching to epithelial cell surfaces [including mucous membranes and epidermis]
59
antibody IgD
-found on B cell surface -functions as a b cell antigen receptor
60
antibody IgG
-most abundant antibody in plasma, accounting for 75-85% of circulating antibodies -main antibody of both secondary and late primary responses -readily fixes and activates complement -protects against bacteria, viruses, and toxins circulating in blood and lymph -crosses placenta and confers passive immunity from mother to foetus
61
antibody IgE
-stem end binds to mast cells/basophils, antigen binding to its receptor end triggers cells to release histamine and other chemicals that mediate inflammation and allergic reaction -secreted by plasma cells in skin, mucosae of GI and respiratory tracts, and tonsils
62
antibody effectiveness
antibodies are effective against extracellular antigens -some pathogens [viruses and some bacteria] enter the cell and not accessed by antibodies [cell mediated immunity most important in these circumstances]
63
cell-mediated immunity
-t-cells undergo clonal selection [recognise antigen via t cell receptor [TCR]] -t-cells recognise peptide bound to MHC molecules [CD4+T-cells-MHC class 2 CD8+T-cells-MHC class 1]
64
helper T cell function in humoral immunity
1 - T(h)cells binds with self-nonself complexes of a B cell has encountered its antigen and is displaying it on MHC 2 on its surface 2 - T(h)cell releases interleukins as costimulatory signals to complete B cell activation
65
helper T cell function in cellular immunity
1 - T(h)cell binds dendritic cell 2 - T(h)cell stimulates dendritic cell to express co-stimulatory molecules 3 - dendritic cell can now activate CD8 cell with help of interleukin 2 secreted by T(h)cell
66
role of CD4+ helper cells
-T(h)1 against intracellular bacteria and protozoa -T(h)2 against extracellular parasites -T(h)9 promote inflammation -allergic inflammation -T(h)17 protective and pathogenic -T(fh) [identified by CXCR5] role in selection and survival of B cells -T(regs) natural development and emigrate from thymus
67
cytotoxic CD8+ T cells
induce cell death [apoptosis]by releasing perforin and granzymes
68
innate chemical defenses
-inflammation -antimicrobial proteins [interferons, complement, others] -fever

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