Complement deficiencies

Question 1

Actions of complement system

Answer 1

chemotaxis, cell lysis and opsonisation

Question 2

C1 inhibitor (C1-INH) protein deficiency

Answer 2

causes hereditary angioedema
C1-INH is a multifunctional serine protease inhibitor
probable mechanism is uncontrolled release of bradykinin resulting in oedema of tissues

Question 3

C1q, C1rs, C2, C4 deficiency (classical pathway components)

Answer 3

predisposes to immune complex disease
e.g. SLE, Henoch-Schonlein Purpura

Question 4

C3 deficiency

Answer 4

causes recurrent bacterial infections

Question 5

C5 deficiency

Answer 5

predisposes to Leiner disease
recurrent diarrhoea, wasting and seborrhoeic dermatitis

Question 6

C5-9 deficiency

Answer 6

encodes the membrane attack complex (MAC)
particularly prone to Neisseria meningitidis infection