Question

Human cells are protected by a variety of surface-bound complement regulators like Select one:

a. CR1
b. Factor I
c. Properdin
d. DAF

Answer 1

Answer:

Hello!

The answer is d. DAF

Explanation:

Decay Accelerating Factor (DAF):

DAF or CD55 is a membrane bound protein found on the surface of lymphocytes, erythrocytes, granulocytes, endothelium and epithelium. DAF has two primary functions:

1. To protect the human cells from complement system mediated destruction.
2. To activate T cells and macrophages.

The complement system functions by the attachment of c3 convertase enzymes to the surface of the pathogen. Therefore, these enzymes possess the ability to accidentally attach to the cell membrane as well. DAF protects cells from the complement system by inhibiting the assemblage of C3 and C5 convertase enzymes.

• CR-1 is a cell surface complement reguator that binds the complement proteins C3b, iC3b and C4b.
• Complement factor 1 or Factor 1 is a regulatory protein responsible for the cleavage of the complement proteins, C3b and C4b.
• Properdin is a fluid phase (present in cytoplasm) complement activator.