04 Complement

  • great for encapsulated bacteria

C3

  • Overview of complement
  • 3 different pathways, next step always MAC

Alternative Pathway

  • destroyed in less than a second if not bound

C3b

  • stable c3b creates more of itself via positive loop

Factor H

Lectin Pathway

Classical pathway

  • Alternative and MBL part of innate immunity

C1

  • IgM: 2 Fc very close together, easy C1 binding
  • IgG: ok complement activation

CRP

  • binds C polysaccharides of bacteria

C3a C3b

MAC

  • aka late complement

C5a

Inhibition

PNH

  • DAF/CD59 deficiency
  • start at RBC lysis
  • Free plasma Hgb thrombogenic
  • Priapism: sustained prolonged erection

C3 Deficiency

  • immune complex: antigen-antibody, usually cleared via complement binding and macrophage

C5-9 deficiency

  • not as bad as c3 deficient

Hereditary Angioedema

  • c1 inhibitor breaks down bradykinin

  • urticaria: histamine, not here
  • Epinephrine doesn't work

  • ace inhibitor block bradykinin breakdown

C3 Nephritic

Hypocomplementemia

  • CH50: classic pathway lysis sheep RBC. Qualitative test, yes or no