Q.51 Match List–I with List–II :
| List–I (Complement protein) |
List–II (Complement pathway) |
||
|---|---|---|---|
| (A) | C1 | (I) | Lectin pathway |
| (B) | C4 | (II) | Classical pathway |
| (C) | Factor B | (III) | Alternative pathway |
| (D) | MASP-1 | (IV) | Classical and lectin pathway |
Choose the correct answer from the options given below:
- (A)–(I); (B)–(III); (C)–(IV); (D)–(II)
- (A)–(IV); (B)–(I); (C)–(III); (D)–(II)
- (A)–(II); (B)–(IV); (C)–(III); (D)–(I)
- (A)–(III); (B)–(II); (C)–(IV); (D)–(I)
Complement Proteins Matching: Classical, Lectin, and Alternative Pathways Explained
Complement proteins like C1, C4, Factor B, and MASP-1 initiate specific immune pathways in the body’s defense system. This article decodes a key matching question on complement pathways with the correct answer and detailed breakdowns.
Correct Answer
The correct matching is (A)–(II); (B)–(IV); (C)–(III); (D)–(I). C1 activates the classical pathway, C4 operates in both classical and lectin pathways, Factor B drives the alternative pathway, and MASP-1 initiates the lectin pathway.
List-I and List-II Breakdown
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C1 (A) pairs with Classical pathway (II): C1 complex (C1q, C1r, C1s) binds to antibody-antigen complexes to kickstart the classical pathway.
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C4 (B) pairs with Classical and lectin pathway (IV): C4 cleaves into C4a and C4b in both pathways, forming part of C3 convertase for amplification.
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Factor B (C) pairs with Alternative pathway (III): Factor B cleaves to Bb, combining with C3b to form the alternative C3 convertase without antibodies.
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MASP-1 (D) pairs with Lectin pathway (I): MASP-1 activates in mannose-binding lectin (MBL) complexes on pathogen carbs, mimicking C1 in the lectin pathway.
Why Other Options Fail
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Option 1: (A)–(I); (B)–(III); (C)–(IV); (D)–(II) Wrong: C1 not lectin; C4 not alternative; Factor B not classical/lectin.
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Option 2: (A)–(IV); (B)–(I); (C)–(III); (D)–(II) Wrong: C1 not dual; C4 not lectin-only; MASP-1 not classical.
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Option 4: (A)–(III); (B)–(II); (C)–(IV); (D)–(I) Wrong: C1 not alternative; C4 not classical-only; Factor B not dual.
Complement Pathways Overview
All pathways converge at C3 for opsonization, inflammation, and lysis via MAC. Classical needs antibodies, lectin detects sugars, alternative amplifies spontaneously.
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