Question

Which type of antibody is the only one capable of crossing the human placenta?

• A. IgA
• B. IgM
• C. IgG
• D. IgE

Hint:

IgG → Only antibody crossing placenta → Provides passive immunity to fetus.

Answer 1

The Correct Option is C

Concept: Antibodies (immunoglobulins) are proteins produced by the immune system to fight pathogens. Different classes of antibodies have distinct structures and functions.
Step 1: Understanding IgG.
IgG is the most abundant immunoglobulin in human serum and plays a crucial role in secondary immune response.
Step 2: Placental transfer.
IgG is the only class of antibody that can cross the placenta from mother to fetus.
Step 3: Significance.

• Provides passive immunity to the fetus
• Protects newborns against infections during early life

Step 4: Eliminating other options.

• IgA: Found in secretions like saliva and milk
• IgM: First antibody produced but too large to cross placenta
• IgE: Involved in allergic reactions

Step 5: Conclusion.
Thus, IgG is the only antibody capable of crossing the human placenta.