Question

Match the following antibodies with their correct description:

Antibody	Description
P. IgE	(i) Cross the placenta
Q. IgG	(ii) Dominant antibody produced in immune responses
R. IgM	(iii) It is found in the mother's milk
S. IgA	(iv) Responsible for autoimmune responses including allergies

• A. P(i), Q(iii), R(ii), S(iv)
• B. P(i), Q(ii), R(iii), S(iv)
• C. P(iv), Q(ii), R(iii), S(i)
• D. P(iv), Q(i), R(ii), S(iii)

Hint:

- IgE is involved in allergic reactions, IgG crosses the placenta to provide immunity to the fetus, IgM is the first response antibody, and IgA is found in mucosal areas like breast milk. 
- These antibodies are key to understanding immune responses and vaccine development.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Each immunoglobulin class has one role it is best known for in immunology: a placental role, an early response role, a mucosal secretion role, and an allergy related role. Matching P, Q, R, S to i, ii, iii, iv means recalling these four defining roles correctly.

Step 2: Key Fact:
IgG is the smallest antibody and the only class that can cross the placenta, giving passive immunity to a newborn. IgM is the largest antibody, built as a pentamer, and is the first class made in an immune response, so it dominates early on. IgA guards mucosal surfaces and is the main antibody in breast milk. IgE binds mast cells and basophils and drives allergic and parasite related responses.

Step 3: Detailed Explanation:
P is IgE, so P matches (iv), the allergic response description.
Q is IgG, so Q matches (i), crossing the placenta.
R is IgM, so R matches (ii), the dominant early antibody.
S is IgA, so S matches (iii), found in mother's milk.
Every other listed combination breaks at least one of these four correct pairings.

Step 4: Final Answer:
The correct matching is P(iv), Q(i), R(ii), S(iii).