complement pathway

Question 1

what activates the

classic complement pathway

Answer 1

antigen-antibody complexes

(IgG or IgM binds antigen and then C1 coimplement protein)

Question 2

what activates the alternative pathway?

Answer 2

• activated by molecules on the surface of microbes
• spontaneous activation

DOES NOTrequire antibodies

Question 3

lectin pathway in complement cascade

needs what to activate it

Answer 3

Microbial surfaces (mannose)

Mannose-biniding lectin binds mannose on surface of microbes

Question 4

what is the starting point of the CLASSIC PATHWAY

Answer 4

C1

C1 inhibitor inhibits (esterase inhibitor) cleavage of C1 into active components

Question 5

MAC

membrane attack complex

is formed by

Answer 5

C5b

C6

C7

C8

C9

Question 6

C3b

FUNCTION?

Answer 6

Opsonization

this causes phagocytosis of encapsulated bacteria

Question 7

if a pt is def in C3b what infections are the suceptable to?

Answer 7

encapsulated organisms

Question 8

C5a

function?

Answer 8

neutrophil chemotaxis!!!

Question 9

what are the two most important opsonins

Answer 9

C3b and IgG

Question 10

C3a, C5a and C4a

stimulate?

Answer 10

Anaphylaxis

Question 11

C3a

stimulate what cells

Answer 11

Mast cells

Basophils

Question 12

deficiency of C1 esterase inhibitor

causes what disease?

Answer 12

hereditary angioedema

• due to unregulated activation of kallikrein –> inc bradykinin

classic findings: edema of skin (especially periorbital) + mucosal surface

CI: never give ACE inhibitor

Question 13

Deficiency of C3

can lead to?

Answer 13

recurrent pyogenic sinus infections and respiratory tract infections.

(especially encapsulated bacteria)

• strept pneumoniae, H. influ

and

**inc susecptibility to type III hypersensitivity rxn

-especially ( glomerulonephritis)

Question 14

def of C5b, C6, C7, C8 or C9 (MAC)

cant form Membrance attack complex.

this incresaed risk for?

Answer 14

Neisseria bacteremia!

( gonoccocal or meningococcal)

Question 15

def in DAF (CD55)

Answer 15

.paraoxysmal nocturnal hemoglobinuria

occurs when RBCs are def in two surface molecules that help protect against the MAC:

• Glycoylphospnoinositol (GPI) which anchors decay accelerating factor (CD55) to plasma membrane
• MAC- inhibitory protein (CD 59)

get chronic intravascular hemolysis–>

• hemosiderinuria
• thrombosis (platelets get destroyed releasing prothrombotic contents)

diagnosis - hams test (lysis rbc at low ph), flow cytometry - look for CD55/59. if not seen then they have it

TX - transfusion, warfarin, ECULIZUMAB.