Immunopathology (5 and 6) Flashcards Preview

EMS - Mechanisms of Disease > Immunopathology (5 and 6) > Flashcards

Flashcards in Immunopathology (5 and 6) Deck (57):
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Innate immune system

Barrier and chemical mechanisms, PRR, cellular (phagocytes, natural killer cells)

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Adaptive immune system

Humoral or cellular

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Pattern recognition receptors

Antigen recognition receptor in the innate system

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What do pattern recognition receptors usually detect?

Pathogen-associated Molecular Patterns (PAMPs) but also Danger Associated Molecular Patterns (DAMP's)

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2 Groups of PRR

1. Cell surface (transmembrane) and intracellular receptors -TLRs, NLRs, RLR's and CLR's
- Fluid-phase soluble molecules

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Fluid-phase recognition molecules

C-type lectin family
- Collections - Mannan-binding Lectin/Surfactant protein A & D
- Recognition of microbal complex carbohydrates

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Fluid-phase recognition molecules role

Neutralisation of pathogen and recruitment of adaptive response

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What do fluid-phase recognition molecules bind via

Carbohydrate-Recognition Domains (CRDs)

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IL1

First cytokine in response to infection makes you feel ill

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Other important cytokines

TNF, IL6, IL23

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Plasmacytoid dendritic cells

Produce IFN (circulate in blood)

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Myeloid dendritic cells

Produce IL12 and IL10 (circulate in blood)

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Natural killer cells

Kill foreign and host cells that have low levels of MHC+ self peptides (self regulatory)

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NK-T cells

T cell and NK surface markers, kill host cells infected with intracellular bacteria

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Plasma cell

First thing engaged with macrophages if infection, informs adaptive immune system what to do, found everywhere

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Neutrophils

Phagocytose and kill bacterial (produce antimicrobial peptides)

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Eosinophils

Kill invading parasites

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Mast cells and basophils

Release TNF, IL-6, IFN in response to bacterial PAMPs

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Adaptive immune response

Unique antigen receptor found on each lymphocyte, in infection undergoes clinical expansion, high degree of specificity

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Primary lymphoid organ

Bone marrow and Thymus

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Secondary lymphoid organ

Spleen (white pulp), lymph node, mucosal surfaces

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Antigen presentation

Antigens are internalised and broken down to peptides, associate with newly synthesised class 2 molecules brought to cell surface

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Peptide are foreign

Recognised by helper T cells which are activated, produce cytokines need by B cells, T cells etc

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What are Histocompability Antigens/HLA?

Glycoproteins found on the surfaces of mammalian cells which make everyone unique

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Class 1

HLA-A, HLA-B, HLA-C

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Class 2

HLA-DP, HLA-DQ, HLA-DR

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Functions of class 1 and class 2 MHC proteins

T cells can only see antigen in associated with MHC proteins (can present many peptides with similar structure)

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MHC class 1 proteins present peptides to

Cytotoxic T cells

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MHC class 2 proteins present peptides to

Helper T cells

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B lymphocytes

Can secrete antibodies (humoral immunity)

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Killer/cytotoxic T cell

Can kill (cellular immunity)

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Helper T cell

Secrete growth factors (cytokines) which control immune response, help B and T cells

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Suppressor T lymphocytes

Dampen down immune response

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Which lymphocytes are the target of HIV?

Helper T lymphocytes

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Th1

Parasites/virsuses

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Th2

Allergies

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Th3

Produces IL-17, fungal defence

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Immunosuppression

A natural/artificial process which turns off immune response (partially/fully) (accidentally/on purpose)

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Immunodeficiency

Lack of an efficient immune system-susceptibility to infections

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Uses of immunosuppression

Transplant rejection, autoimmune disease and lymphoprolfierative diseases

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Hypersensitivity

Undesirable, damaging and sometime fatal reactions produced by normal immune system in a pre-sensitised host

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Allergy

Altered reactivity

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Hypersensitivity Type 1

IgE mediated

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Hypersensitivity Type 2

Cytotoxic

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Hypersensitivity Type 3

Immune complex reaction

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Hypersensitivity Type 4

Cell mediated reaction (DTH)

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Examples of allergic diseases

Asthma, rhinitis, dermatitis, food allergy

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Hypersensitivity Type 3 reaction

- IgG + Ag = AgAb complex
- FcR in complex bind C1q
- Complement activation leads to generation of activated complement fragments
- C5a - attractant for neutrophils
- C3b - opsonin
- Attempted phagocytosis of complexes - release of enzymes, O2 radicals
- Tissue damage

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Hypersensitivity Type 4 reaction

- Perivascular infiltration of lymphocytes and monocytes
- Langherhan's cells present neo-antigen to T cells
- Ag-specific T cells release cytokines - recruitment of macrophages (non Ag-specific)
- Activated macrophages cause tissue damage
- Requires previous exposure to antigen

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Contact dermatitis

Combination of DTH and cytotoxic reaction, antigen presentation by APC, Keratinocytes present to CTL precursors

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Examples of contact dermatitis

Posion ivy and Nickel (Nickel acts as hapten with epidermal proteins)

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What are granulomas?

Focal collections of inflammatory cells in tissues - macrophages, epitheloid cells, giant cells, lymphocytes

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T cell granulomas

Th1 type and secrete IL2 and IFNy

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What is released by macrophages to initiate granuloma formation?

IL-12

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Granulomatous diseases examples

- Mycobacterial (TB, atypical mycobacteria, leprosy)
- Sarcoidosis
- Wegener's Granulomatosis
- Crohn's disease

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Tuberculoid Leprosy

Th1 protective

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Lepromatous Leprosy

Th2 non-protective