Opsonization is the process of
1. coating of foreign substances by antibody
2. coating of foreign substances by MHC
3. coating of foreign substances by TCR
4. none of the given options is correct

What Is Opsonization?

Opsonization is a crucial immune process where foreign substances (like bacteria, viruses, or other pathogens) are coated with specific molecules—primarily antibodies or complement proteins—to enhance their recognition and uptake by phagocytic cells like macrophages and neutrophils.

How It Works: The Mechanism

1. Antibodies (mainly IgG) bind to antigens on the pathogen surface.

2. This “coating” acts like a signal or tag.

3. Phagocytic cells recognize these tagged invaders via their Fc receptors.

4. The pathogen is engulfed and destroyed.

This process is essential for efficient immune clearance, especially against encapsulated bacteria that evade immune detection.

Why the Other Options Are Incorrect

• MHC (Major Histocompatibility Complex) presents antigens to T cells but doesn’t coat pathogens.

• TCR (T-cell receptor) is involved in antigen recognition, not in tagging or coating.

• So, only antibodies and complement proteins are involved in opsonization.

Complement System’s Role

Besides antibodies, complement protein C3b can also function as an opsonin, enhancing phagocytosis even in the absence of antibodies during early infection stages.

Why Opsonization Is Important

• Enhances phagocytic efficiency

• Clears pathogens quickly

• Bridges innate and adaptive immunity

Conclusion

Opsonization is the immune system’s way of “flagging” invaders, making them easier to eliminate. It mainly involves the coating of foreign substances with antibodies—making option 1 the correct and scientifically accurate choice.