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USMLE immunology > complement > Flashcards

complement Flashcards

1
Q

What is the role of the membrane attack complex (MAC)?

A

The MAC defends against gram-negative bacteria by causing cytolysis of the target cell.

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2
Q

What test is used to screen for activation of the classical complement pathway?

A

The CH50 test is used to screen for activation of the classical complement pathway.

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3
Q

Which immunoglobulins mediate the classical complement pathway?

A

The classical complement pathway is mediated by IgG and IgM.

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4
Q

What triggers the alternative complement pathway?

A

also called the spontaneous pathway , where 3b binds to amino and hydroxyl groupsThe alternative pathway is triggered by microbe surface molecules.

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5
Q

What triggers the lectin complement pathway?

A

The lectin pathway is triggered by mannose or other sugars on the surface of microbes.

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6
Q

What are the functions of C3b?

A

C3b functions as an opsonin to enhance phagocytosis and also helps clear immune complexes.

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7
Q

What are the roles of C3a, C4a, and C5a?

A

C3a, C4a, and C5a are involved in anaphylaxis, and C5a specifically plays a role in neutrophil chemotaxis.

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8
Q

Which components form the MAC?

A

The MAC is formed by components C5b through C9.

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9
Q

What are the primary opsonins in bacterial defense?

A

The primary opsonins are C3b and IgG.

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10
Q

How does C3b bind to bacteria?

A

C3b binds to lipopolysaccharides on the surface of bacteria.

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11
Q

Why is the MAC particularly important for Neisseria species?

A

The MAC is critical for neutralizing Neisseria species. Its deficiency results in recurrent infections.

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12
Q

What inhibitors prevent complement activation on self cells?

A

Decay-accelerating factor (DAF, also called CD55) and C1 esterase inhibitor prevent complement activation on self cells such as red blood cells.
as well as the H factor

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13
Q

What mnemonic can help you remember the classical pathway?

A

“General Motors makes classic cars” helps remember the classical pathway.

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14
Q

What mnemonic can help you recall the MAC components’ importance for Neisseria?

A

“Get ‘Neis’ (nice) Big MACs from 5-9 pm” helps recall that the MAC (C5b-9) is important for Neisseria.

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15
Q

where are the amino and hydroxyl groups used for the alternative pathway found ?

A

LPS
fungal cell walls
viral envlopes

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16
Q

what is the lectin pathway ?

A

it is the third pathway for complement activation where it is activated by mannose , once its bound MASPS are activated
which then claves C2 and C4 into C2b and C4b which fuse together to form C2b4b which. is C3 convertase

17
Q

whats common betweeen the lectin pathway and the classcical pathway ?

A

they both use C2b4b too make C3 convertase

18
Q

what is the function of IL 6 ?

A

stimulates the liver for the formation of CRP
activates classical pathway via C1 binding

19
Q

which complement are anaphyltoxins ?

A

C3a and C5a

20
Q

what type of bacteria is mainly affected by complement ?

A

encapsulated

21
Q

why does paroxysmal nocturnal hemoglobinura ?

A

due to a deficiency in DAF/CD95

22
Q

what is the presentation off paroxysmal nocturnal hemoglobinuria ?

A

sudden hemolysis att nnight
thrombosis
priapism
dysphagia
abdominal pain
low haptglobin and dark urine

23
Q

what is the presentation of recurrent C3 deficiency ?

A

recurrent infections of encapsulated bacteria
pneumococcal and h influenza
GN
type 3 hypersensitivity syndrome

24
Q

what is the presentation of C5 to C9 deficiency ?

A

recurrent niesseria infection, most oftn presents as meningitis

25
Q

what is the presentation of C1 inhibitor deficiency ?

A

hereditary angioedema
without urticaria

26
Q

what specific must always be avoided with hereditary angioedema?

A

ACE inhibitor

27
Q

what diseases are associated with low complement levels ?

A

lupus
MPN
post strep GN

28
Q

which complement is sed in thee clearance of antigen antibody complexes ?

A

C3b

29
Q

terminal compliment deficiencies ?

A

higher risk of neisseria

30
Q

what gene mutation is associated with paroxysmal nocturnal hemoglobinuria ?

A

PIGA

31
Q

function of
C3b
C3a, C4a, C5a
C5a
5b-9

A

opsonization
anaphyltoxin
neutrophil chemotaxis
MAC

USMLE immunology (12 decks)

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