The following statements were made about the alternative pathway of Complement activation in the immune system:

A. The pathway is initiated when antibodies bind to pathogen.
B. The pathway is initiated by spontaneous hydrolysis of serum Complement.
C. The pathway uses the same C3- and C5-convertases as the lectin pathway.
D. The pathway can be initiated by properdin and thrombin.

Which one of the following options represents the combination of all correct statements?

Correct option is C

EXPLANATION-

A. The pathway is initiated when antibodies bind to pathogen.
This is incorrect.
This describes the classical pathway, not the alternative pathway. The alternative pathway is antibody-independent.

B. The pathway is initiated by spontaneous hydrolysis of serum Complement.
This is correct.​
The alternative pathway is continuously active at low levels via spontaneous hydrolysis of C3 (often referred to as "tick-over").

C. The pathway uses the same C3- and C5-convertases as the lectin pathway.
This is incorrect.​
The lectin and classical pathways share the C3 convertase C4b2a, while the alternative pathway uses C3bBb.
So, they do not use the same C3/C5 convertases.

D. The pathway can be initiated by properdin and thrombin.
This is correct.
Properdin stabilizes the C3 convertase of the alternative pathway.
Thrombin, though mainly a coagulation factor, has been shown to activate C3 and C5, and is implicated in complement activation under inflammatory conditions.

So, the correct option is (c) B and D.