Question

Which one of these acute phase proteins has strong affinity to iron?

• A. Albumin
• B. Ceruloplasmin
• C. C-reactive protein
• D. Transferrin

Hint:

Metal-Binding Proteins:
- Transferrin $\rightarrow$ Iron (Fe).
- Ceruloplasmin $\rightarrow$ Copper (Cu).
- Metallothionein $\rightarrow$ Heavy metals (Zn, Cd, Hg).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify an acute phase protein (APP) that plays a role in immunity by binding and sequestering iron.
Detailed Explanation:

• Acute Phase Proteins: These are proteins whose plasma concentrations increase (positive APPs) or decrease (negative APPs) in response to inflammation or infection.

• Transferrin: Transferrin is a glycoprotein that binds free iron ($Fe^{3+}$) with extremely high affinity and transports it through the blood.

• Nutritional Immunity: Many pathogenic bacteria require free iron for growth and replication. During an infection, the body increases transferrin activity or other iron-binding proteins (like lactoferrin) to "hide" iron from the pathogens. This biological strategy is called nutritional immunity.

• Other Options:
• Albumin: Primary transport protein but not specifically for iron affinity.

• Ceruloplasmin: Binds and transports copper.

• C-reactive protein (CRP): Binds to phosphocholine on dead cells or bacteria to activate the complement system.

Step 3: Final Answer:
Transferrin is the protein with a strong affinity for iron.