Question

Eosinophils are many times smaller than most parasites. How do they defend against something so much larger than themselves?

Answer 1

Eosinophils with a Size of about 12 μm,Are much smaller than Most Paraites.So they are not able to Engulf the Paraistes.But they manage to kill the Parasites .This is Done by-

*Eosinophils attaches to juvenile form of parasites .

*Eosniophil secreates -

a)Hydrolytic enzymes ( from lysosomes)

b)Reactive Oxygen Species

c) polypeptide that has larvicidal activity.

By the Helps of these Hyrdolytic Enzymes,Reactive Oxygen Species & Larvicidal Polypeptide,The small Eosinophils manage to kill Large Parasites.

Proteins secreated from eosinophil granules,which has ability to kill parasites include

1.MBP(Major Basic Proteins)-This protein released from Eosinophil cause

a)release of histamine from mast cells and basophils

b)Activates neutrophils & alveolar macrophages

2. ECP(Eosinophil cationic protein)-(Also called ribonuclease 3 ),Released during Degranulation of Eosinophils.This is a cytotoxic protein,which plays a role in defense against parasitic infections.

3.Other Proteins-

*a)EDN(eosinophil-derived neurotoxin)- have antiviral activity

b)EPO(Eosinophil peroxidase)-It helps formation of bacteriocidal reactive oxygen species,& disruption of bacterial cell walls.

By these variety of Actions Eosinophil manages to kills Parasites which are very large in size compared to Eosinophil.