C4 antibody mediated immunity Flashcards

1
Q

antibody specificity and production

A

produced by b lymphocytes
can only attach to their specific antigen
pathogen can be recognised by multiple antibodies- each type is specific to a diff antigen of the pathogen (surface/internal/excreted)

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2
Q

how can antibodies mediate in a number of responses

A

interact with complement
-cell lysis/attach innate cell
ineract with phagocytic cells (via fc portion of anti b)
can have neutralising effect-eg block viral entry into cell

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3
Q

what enhances rate of phagocytosis

A

if the target is opsonised (increases >4000x)

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4
Q

neutralisation of a toxin by an antibody

A

-toxin binds to cellular receptors
-endocytosis of toxin:receptor complexes
-dissociation of toxin releases its active chain which poisons cell
-antibody protects cell by blocking binding of toxin

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5
Q

how antibodies can mediate in killling by NK cells

A

-antibody binds antigens on surface of target cells
-Fc receptors on NK cells recognise bound antibody
-cross linking of Fc receptors signals the NK cell to kill target cell
-target cell dies by apoptosis

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6
Q

where is most IgA present

A

gut, produce 50mg/kg/day

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7
Q

what occurs in IgA deficiency and symptoms

A

recurrent bacterial, enteroviral or protozoal infections of the respiratory and GI tract
is asymptomatic because IgM exerts compensatory function

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8
Q

what is IgA important for

A

important in defense against intestinal pathogens (rotavirus)
present in genital-urinary tract secretions can protect against HIV- neutralise viral particles

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9
Q

IgG importantance and abundance where

A

is the main Ig class produced during immune response
>75% of total circulating Igs in the blood

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10
Q

how does IgG mediate phagocytosis

A

by macrophages/neutrophils- opsonin induces enhanced endosomal maturation and efficient degradation of lysosomal contents

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11
Q

how does IgG mediate antibody dependent cellular cytotoxity

A

by NK cells- FcyRIIIa-cross-linking on NK cells triggers activation and release of perforin and granzymes- induces apoptosis of infected/abnormal cells

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12
Q

how does IgG mediate degranulation of neutrophils, eosinophils and mast cells

A

when FcyRs croos-linking triggers rapid degranulation-generation and release of reactive oxygen (ROS) and reactive nitrogen species (RNS)-potent bactericidal effects

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13
Q

what 3 things do IgG mediate

A
  1. phagocytosis by macrophages/neutrophils
  2. antibody dependent cellular cytotoxicity by NK cells
  3. degranulation of neutrophils, eosinophils and mast cells
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14
Q

where is IgM the first Ig to appear in and where is it present

A

first Ig isotype to appear during phylogeny, ontogeny, and host immune responses
present in new born babies (natural IgM
produced in response to antigenic stimulation of B cells - adapive IgM

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15
Q

what can IgM antibodies recognise

A

a wide range of different microbial components- viral antigens and bacterial toxins
high avidity of polymeric IgM
meaning it can immobilise target at a site-stop bacteria spreading

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16
Q

what is IgE involved in and what is it mediated by

A

involved in protection against metazoan parasitea, environmental toxins, and vemons
mediated via degranulation of granulocytes

17
Q

how does IgE mediated activation occur

A

through FceRI on mast cells and basophils/multivalent antigens cross-link the receptor bound IgE to trigger degranulation and the release of pre formed mediators

18
Q

what are the products released by granulocytes and what does it protect

A

can protect against bacterial infection
released IL-6 helps induce protection against Klebsiella pneumoniae- recruit other innate cells as neutrophils

19
Q

how does IgE work to neutralise venom

A

specific IgE bound to mast cells recognises specific antigen in the venom
IgE activation causes mast cell degranulation and release of enzymes that inactivate the venom

20
Q

what do the majority of antigen naive mature B cells express

A

surface IgD and IgM

21
Q

what do some tonsil IgM+IgD+ follicular B cells lose but retain and become

A

lose IgM but retain IgD and become plasma B cells

22
Q

half life of IgD and serum conc

A

IgD half life of 3 days
serum conc is variable- poss due to genetic/environmental factors

23
Q

what might IgD be protective against

A

mucosal pathogens- binds to moraxella catarrhalis and haemophilus influenzae