Alternative Complement Pathway

When C3b encounters normal cells, it is rapidly eliminated through the combined interactions of factors _ ___ _ .

H and I

The C3bBb complex is stabilized by the presence of properdin (P), yielding ________ .

C3bBbP

Membrane Attack Complex: In the activation of the classical pathway, the MAC is initiated by the enzymatic activity of component __________ on C5.

C4b2a3b

Membrane Attack Complex: In either classical or alternative pathways, the formation of __ _______________ e is necessary

C5 convertase

The C3b2BbP complex acts as a __ ______________ and initiates the later steps of complement activation

C5 convertase

Membrane Attack Complex: In the alternative pathway, it is __________ that has the ability to cleave C5.

C3b2Bb

As a result of this action, factor B is cleaved, yielding a cleavage product known as __ .

Bb

This complex cleaves C3 into additional ___ and ____ . C3b, therefore, acts as a positive feedback mechanism for driving the alternative pathway.

C3a and C3b

Activation of the alternative pathway requires that a ___ molecule be bound to the surface of a target cell.

C3b

Membrane Attack Complex: Component C5 is split into the fragments C5a (a potent anaphylatoxin) and C5b; the C5b fragment attaches to cell membranes and can continue the complement cascade by initiating the membrane attachment of __, __ and __

C6, C7, and C8.

In this pathway, complement component factor D is ____________ to C1s in the classical pathway; factor B is ____________ to C2; and the cleavage product C3b is ____________ to C4. Also, factor C3bBbP is _____________ to C4b2a, and C3b2BbP is _____________ to C4b2a3b in the classical pathway.

analogous

Lectin Complement Pathway has similar steps as _______ __________

classic pathway

The alternative pathway is activated by surface contacts with _________ ____________ and artificial surfaces such as dialysis membranes and dextran polymers.

complex molecules

The accumulation of C3b on microbial cell surfaces is associated with attachment of C3b to ______ _ .

factor B

The complex of C3b and factor B is then acted on by ________ _ .

factor D

Small amounts of C3b are generated continuously, owing to the spontaneous ______________ cleavage of the C3 molecule

hydrolytic

Membrane Attack Complex: After the attachment of C9 to the C5b678 complex, a small transmembrane channel or pore is formed in the lipid bilayer of the cell membrane, and this allows for ________ ____ and subsequent death of the cell.

osmotic lysis

There are four important proteins in this pathway: factor D, factor B, ___________ , and C3.

properdin

Membrane Attack Complex: The final step of complement activation is the formation of the MAC, which is composed of the ______________ components of the complement sequence

terminal