Nelson- Hypersensitivity Flashcards by Sarah Carlson

What is innate immunity?

Pre-existing, non-specific defense mechanism, present prior to infection. Evolved to recognize PAMPS and DAMPS and protect individual from infection.

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What is adaptive immunity?

Reactive mechanisms stimulated by specific microb capable of recognizing microbial and non-microbial substances.

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What are some of the component of innate immunity?

Epithelial barriers
phagocytic cells
Eosino, Baso, mast
NK
Plasma proteins (complement)

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What are the two types of adaptive immunity?

Humoral- extracellular microbes and toxins

Cell-mediated- intracellular microbes, tumor cells

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What are naive lymphocytes?

mature lymphocytes which haven’t yet encountered the antigen they’re specified for

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What are activated lymphocytes? (2 type)

differentiate into effector cells that eliminate the pathogen and memory cells that are reactivated upon second exposure.

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Function of CD4 T cell

Secrete cytokines, help B cells become plasma cells

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Function of CD8 T cell

kill virus infected cells, neoplastic and donor graft cells

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Function of B lymphocyte

differentiate into plasma cells that produce IG to kill encapsulated bacteria and act as APCs w/ CD4 cells

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Function of NK

kill virus infected and neoplastic cells

release IFNy

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Function of macrophage

phagocytosis and cytokine production

APCs for T cells

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Function of DC

APCs to T cells

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What are generative lymphoid organs?

Sites where T and B lymphocytes mature and become competent to respond to antigens

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What are peripheral lymphoid organs?

Sites where the adaptive IR is initiated (lymph nodes and spleen)

B cells in follicles
T cells in paracortical regions

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HLA-A, B and C genes code for what class of MHC. What does that MHC do?

MHC I
Display proteins derived from the cytoplasm
Recognized by CD8 T lymphocytes and NK cells

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HLA-DP, DQ, DR genes code for what class of MHC. What does that MHC do?

MHC II
Display antigens that have been internalized into vesicles
Recognized by CD4 T lymphocytes

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What are the two reasons we do HLA testing?

Diseases are associated w/ the inheritance of HLA alleles. HLA testing is used to determine disease risk.
HLA testing is also used in transplantation work up. Close matches increase chances of graft survival.

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What is a hypersensitivity reactoin?

Individuals previously exposed to an antigen are sensitized. With second exposure some ppl develop pathologic immune response to antigen.

What are the 4 types of hypersensitivity reacionts?

Immediate
Anti-body mediated
Immune complex mediated
Cell mediated

ACID- Allergic, Cell-mediated cytotoxic, immune complex, delayed

What is a type I hypersensitivity rxn?

FIRST and FAST
Rapid rxn occuring w/in minutes after Ag binds Ab bound to mast cells.
Occurs in individuals previously sensitized to the antigen.
Mediated by IgE Ab dependent activation of mast cells.

What is atopy?

The predisposition to develop localized immediate hypersensitivity rxns.

Positive family hx is found in 50% of individuals.

Atopic individuals tend to have what two things…

Higher IgE levels and more IL-4 producing Th2 cells.

What is the mechanism of a type 1 hypersensitivity rxn?

Introduction of allergen>
stimulates Th2 response and IgE production>
IgE binds to Fc receptors on mast cells>
Subsequent exposure to allergen activates mast cells to secrete mediators responsible for the immediate and late-phase rxns

What is the immediate phase in type 1 rxn?

vasodilatoin
congestion
edema

What is the late phase in a type 1 rxn?

inflammatory infiltrate filled w/: eosinophils neutrophils T cells

What is a localized allergic rxn?

Something that sticks to one spot!

What are common examples of localized allergic rxns?

allergic rhinitis (hay fever) bronchial asthma urticaria (hives) allergic gastroenteritis (food allergy) (pollens, molds, house, dust, animal dander, food, medications, blood products, venom)

How do you tx and prevent localized rxns?

Avoid allergen. Use medications that inhibit the release of histamine from mast cells. Immunotherapy

What is systemic anaphylaxis?

Life threatening allergic reaction characterized by vascular shock, widespread edema, difficulty breathing (d/t massive mast cell activation)

What is the mechanism of systemic anaphylaxis?

Massive mast cell activation--> vasoactive amines released in mins Death in mins> d/t upper airway edema and respiratory failure from bronchial constriction/shock

What are common inciting agents in fatal systemic anaphylaxis?

Therapeutic agents (beta-lactam antibiotics-penicillin, cephalosporins, radiocontrast agents) Food products (peanuts, seafood) Insect toxin (bee/wasp sting) Latex allergy

What is a type II hypersensitivity rxn?

Antibodies react w/ antigens intrinsic to cell membrane/matrix or w/ exogenous antigens that are on the cell surface.

What is the mechanism of injury of a type II rxn?

1. Opsonization of cells by Ab and complement components and ingestion by phagocytes 2. Inflammation induced by Ab binding to Fc receptors of leukocytes and by complement breakdown products 3. Anti-receptor Ab disturb the normal fxn of receptors.

What are some examples of a type II rxnn?

Myasthenia gravis- ACh receptor Autoimmune hemolytic anemia (RBC membrane proteins) Autoimmune throbocytopenic purpura (platelet proteins--> bleeding) Penphigus vulgaris (desmosomes) Vasculitis (activation of neutrophils to release granules proteins leading to vasculitis) Acute rheumatic fever Graves disease

What is good pasture's syndrome

Antibodies act against the glomeruli basement membrane in the kidney's and alveoli in the lungs. It's possible to detect the Abs for diagnostic purposes.

What is a type III hypersensitivity?

Cause by Ag-Ab complexes which cause inflammation at sites where they're deposited.

How do the Ag-Ab complexes cause injury in type III hypersensitivity?

When there is excessive Ab production in circulation the complexes become deposited on the vessel walls. The Fc receptor is bound by a WBC and the vessels are part of the collateral damage from the complex destruction.

What are some examples of this type of rxn?

``` SLE Postreptococcal glomerulonephritis Reactive arthritis Polyarteritis nodosa Serum sickness ```

Why are the clinical manifestations of type III hypersensitivity so diverse?

Because we have Abs to many different things...?

Define type IV hypersensitivity.

``` Caused by T cell mediated immunity (NO Abs!) T cells (CD4/8) are sensitized to exog/endog antigens. T cell immune response to these antigens--> tisue injury. ```

How does type IV hypersensitivity injure the body?

Delayed type rxn- repeat exposure to the antigen the CD40Th1 cells respond to tissue antigens by secreting cytokines that stimulate inflammation and activate phagocytes--> tissue injury. T cell mediated cytotoxicity--TK cells (CD8 directly kill tissue cells)

What is the mechanism of granuloma formation?

CD4 T cells surround an area and release cytokines

What are examples of type IV hypersensitivity?

``` Mantoux Test Type I diabetes MS Rheumatoid arthritis Chrons Peripheral neuropathy; Guillian Barre Contact sensitivity ```