Lectin/Alternative Pathway Overview

lectins

recognize carbohydrate components (PAMPs), similar to antibodies

MBL

the first lectin demonstrated to initiate complement activation, binds residues on salmonella, listeria, fungi, and some viruses

collectins

MBL in the liver is this general group of innate immune function, found in liver

MASP

three types, but the second associates with MBL to cleave C2 and C4

MASP-2

specific MASP that associates with MBL to form C3 convertase

mannose associated serine protease

full name for MASP

alternative

complement pathway that does not require C1q or MBL, has multiple mechanisms

fluid phase

mechanism for alternative pathway that requires factor B and D to form non-membrane bound C3 convertase

B and D

the two factors required for both fluid and membrane-bound phase C3 convertase formation

membrane bound

mechanism for alternative pathway that requires fluid-phase C3 convertase to form C3b which can bind the membrane and associate with factors B and D to form C3 convertase

D

factor __ that cleaves Ba from factor B to form Bb and the final C3 convertase

B

factor __ that initially binds C3 (fluid-phase) or C3b (membrane-bound)

C3(H₂O)Bb

full name for fluid-phase C3 convertase

properdin

mechanism for alternative pathway where factor P binds and stabilizes C3bBb complex (C3 convertase) and C3bBbC3b complex (C5 convertase)

factor P

another name for properdin

C3 and C5

the two convertases that properdin stabilizes

C3bBb

full name for C3 convertase that is either membrane bound or stabilized by properdin

C3bBbC3b

full name for C5 convertase stabilized by properdin

Lewis Pillemer

scientist who discovered properdin using yeast to extract membrane-bound properdin and tested if C3 could be activated with or without it