Question

Which of the following BEST explains the timing of the classical pathway of complement fixation,relative to the other pathways of complement fixation, against a pathogen in an individual who hasnever been exposed to said pathogen?
A.No target for C1qrs exists on the surface of the pathogen in the earliest stages of theresponse to it.

B.The chemical environment of the pathogen's surface favors the spontaneous activation ofsoluble C3 immediately upon exposure to the pathogen.

C.C1qrs immediately recognizes carbohydrate antigens on the surface of the pathogen,allowing for rapid formation of the C4b2a C3 convertase.

D.The pathogen expresses one or more factors on its surface that act as negative regulators ofC3 convertase formation.

E.None of the above

Answer 1

Answer:

A

Explanation:

1. There are 3 pathways of complement activation:

i) the classical pathway;

ii) the MB-lectin pathway; and

iii) the alternative pathway.

2. The classical complement pathway;  for activation, it requires antigen(Ag) antibody(Ab) complexes.

3. While the other pathways can be activated by various ways.

as here,  No target for C1qrs exists on the surface of the pathogen in the earliest stages of the response to it.