Q.63 Which protein/s are present in neutrophil?

1. Collagenase
2. Leukotrienes
3. Defensins
4. Cytokines
5. α-1 antitrypsin

Choose the correct answer from the options given below :

1. A, B, C only
2. A, B, D, E only
3. A, C, E only
4. B, C, D, E only

   Correct Answer: C (A, C, E only)

   Neutrophils contain specific granule proteins critical for innate immunity, including antimicrobial and proteolytic enzymes stored in azurophilic, specific, and gelatinase granules.

   Option Analysis

   A. Collagenase
   Correct. Neutrophils produce collagenase (a matrix metalloproteinase, often MMP-8/neutrophil collagenase) in tertiary/gelatinase granules, aiding tissue migration and extracellular matrix degradation during inflammation.

   B. Leukotrienes
   Incorrect. Leukotrienes are lipid mediators (eicosanoids) synthesized de novo from arachidonic acid via 5-lipoxygenase pathway upon neutrophil activation, not pre-stored proteins.​

   C. Defensins
   Correct. α-Defensins (human neutrophil peptides HNP1-4) are abundant cationic antimicrobial peptides in azurophilic/primary granules, providing direct pathogen-killing activity.

   D. Cytokines
   Incorrect. Cytokines (e.g., IL-8, TNF-α) are small signaling proteins secreted by activated neutrophils but not stored as preformed granule proteins; they are transcribed and synthesized on demand.​

   E. α-1 antitrypsin
   Correct. This serine protease inhibitor is present in neutrophil secondary/specific granules, protecting tissues from excessive proteolysis by neutrophil elastase and other enzymes.​

   Introduction to Neutrophil Proteins

   Neutrophil proteins in granules enable rapid immune responses, with collagenase, defensins, and α-1 antitrypsin as key components for matrix degradation, antimicrobial defense, and protease regulation—essential for GATE Life Sciences exam prep on innate immunity.

   Neutrophil Granule Composition

   Neutrophils feature four granule types:

   • Azurophilic (primary): Defensins, elastase, myeloperoxidase.

   • Specific (secondary): Lactoferrin, α-1 antitrypsin, lysozyme.​

   • Gelatinase (tertiary): Collagenase (MMP-8), gelatinase B.​

   • Secretory vesicles: CD11b/CD18 integrins.​

   Leukotrienes and cytokines are not granule-stored but dynamically produced.​

   GATE Exam Insights

   Focus on granule-specific proteins for MCQs. Option C (A, C, E) matches confirmed neutrophil contents.

   Protein	Present in Neutrophil?	Granule Type	Function
   Collagenase ​	Yes	Tertiary	ECM breakdown
   Leukotrienes	No	N/A	Lipid mediators
   Defensins ​	Yes	Primary	Antimicrobial
   Cytokines	No	N/A	Signaling
   α-1 Antitrypsin ​	Yes	Secondary	Protease inhibition