October 13, 2010

USMLE 1 Question 9

A carpenter gets a splinter of wood embedded in his finger pulp.

What is the first line of defense against this foreign body?

a) Macrophages
b) Neutrophils
c) B-lymphocytes
d) T-Lymphocytes
e) Monocytes

The correct answer is B

Neutrophils, which are also known as polymorphonuclear leukocytes (PMN), represent 50 to 60% of the total circulating leukocytes and constitute the "first line of defence" against infectious agents or "nonself" substances that penetrate the body's physical barriers.

Once an inflammatory response is initiated, neutrophils are the first cells to be recruited to sites of infection or injury.

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