FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam 2026 - Free NABP Practice Questions and Study Guide

Leukocytes, or white blood cells, serve as the first line of defense against microorganisms. This group of cells plays a crucial role in the immune response, as they are primarily involved in protecting the body from infections and foreign invaders. Within leukocytes, various types exist, each with specific functions that contribute to the body's overall immune system.

Among leukocytes, neutrophils are particularly significant as they are often the first responders to sites of infection. They are specialized in phagocytosing (engulfing and digesting) pathogens, which makes them vital in the immediate immune response. While neutrophils represent a key subset of leukocytes, stating that leukocytes as a whole provide the first line of defense encompasses all types of white blood cells working together, including lymphocytes and monocytes, each playing a role in various immune functions.

The other options do not fulfill the role of initial responders to microorganisms. Platelets are primarily involved in blood clotting rather than immune response. Erythrocytes, or red blood cells, transport oxygen and do not have any direct role in fighting infections. Thus, leukocytes collectively stand as the first responders to microbial infections, making them the appropriate choice for this question.