Question

What is the main feature of chemotaxis as observed in white blood cells?

• A. Increased random movement of neutrophils
• B. Increased adhesiveness to intima
• C. Increased phagocytosis
• D. Unidirectional locomotion of neutrophils

Hint:

The key word is directed: movement up a gradient, not random and not adhesion.

Answer 1

The Correct Option is D

Correct answer: Unidirectional locomotion of neutrophils.
Step 1: Chemotaxis is the directed, unidirectional movement of leukocytes up a concentration gradient of chemotactic molecules. The cell crawls toward the highest concentration of the chemoattractant.
Step 2: Granulocytes and monocytes respond strongly, and lymphocytes to a lesser extent. Chemoattractants include bacterial products (exogenous) and endogenous mediators such as complement C5a, the lipoxygenase product LTB4, and chemokines.
Step 3: Why not the others. Random movement is not chemotaxis; chemotaxis is directed. Increased adhesiveness to the intima is the adhesion or margination step, a separate event. Increased phagocytosis is a later step after the cell reaches the target.
Ref: Robbins, acute inflammation.