This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
What is the main feature of chemotaxis as observed in white blood cells? 
Select and explain. 
A. Increased random movement of neutrophils, B. Increased adhesiveness to intima, C. Increased phagocytosis, D. Unidirectional locomotion of neutrophils
D: Unidirectional locomotion of neutrophils
Answer: D: Unidirectional locomotion of neutrophils 
Explanation: Chemotaxis is defined as unidirectional movement of leukocytes up a concentration gradient of chemotactic molecules. All granulocytes, monocytes and to a lesser extent lymphocytes respond to chemotactic stimuli with varying rates of speed. Chemoattractants are exogenous or endogenous in nature. Exogenous agents are bacterial products. Endogenous mediators are:Components of complement pathway C5aProducts of lipoxygenase pathway LTB4Cytokines paicularly those of chemokine familyRef: Robbins Pathologic Basis of Disease, 6th Edition, Page 61