Question 63:
Immune cells that ingest large particles and cells by phagocytosis are called:
The correct answer is (A) Macrophages.
Macrophages are professional phagocytes that engulf large particles (>0.5 μm) and whole cells via phagocytosis, using receptors like Fcγ, complement, and scavenger receptors to internalize pathogens, apoptotic cells, and debris.
Option Breakdown
(A) Macrophages
Correct; tissue-resident and monocyte-derived macrophages form phagocytic cups via actin remodeling, fuse lysosomes to phagosomes, and kill via ROS, NO, and enzymes. Key in innate immunity and homeostasis.
(B) B lymphocytes
B cells produce antibodies and present antigens but lack phagocytic machinery; they internalize via receptor-mediated endocytosis, not phagocytosis of large particles.
(C) Cytotoxic T cells
CD8+ CTLs kill virally infected/target cells via perforin/granzyme or FasL, without phagocytic capacity.
(D) Helper T cells
CD4+ Th cells coordinate adaptive immunity via cytokine secretion and licensing APCs, non-phagocytic.
Introduction to Immune Cells Phagocytosis Large Particles
Immune cells phagocytosis large particles defines macrophages as primary phagocytes engulfing bacteria, apoptotic bodies, and debris >0.5 μm. Essential for GATE Life Sciences immunology, distinguishing professional phagocytes from lymphocytes.
Macrophage Phagocytosis Mechanism
Pattern recognition receptors (mannose, SR-A) bind PAMPs/opsonins, trigger actin polymerization for pseudopod extension, phagosome closure, and lysosomal fusion. M1/M2 polarization modulates pro/anti-inflammatory responses post-phagocytosis.
Tingible body macrophages clear apoptotic lymphocytes in germinal centers.
Immune Cell Functions Comparison Table
| Cell Type | Phagocytosis? | Primary Role | Particle Size |
|---|---|---|---|
| Macrophages | Yes | Engulf large particles | >0.5 μm |
| B Lymphocytes | No | Antibody production | Endocytosis |
| Cytotoxic T Cells | No | Target cell killing | Contact-based |
| Helper T Cells | No | Cytokine coordination | N/A |
Confirms immune cells phagocytosis large particles = macrophages.
Exam Context for Life Sciences Students
Links prior lipids (phosphatidylserine flip signals phagocytosis), alkalosis (affects immune function), enzyme kinetics (lysosomal hydrolases); master “professional phagocytes = macrophages/dendrites/neutrophils” for PYQs.
