What is normally the most common type of leukocyte in a blood sample?

The most common type of leukocyte in a blood sample is the neutrophil. Neutrophils play a critical role in the body's immune response, particularly in combating bacterial infections. They are a type of granulocyte and are characterized by their multi-lobed nucleus and granular cytoplasm, which contains enzymes that help break down pathogens.

In a typical differential white blood cell count, neutrophils usually account for approximately 50-70% of the total white blood cell count in a healthy individual. Their prevalence is vital for the first line of defense against infections; they respond quickly to sites of inflammation and are often the first immune cells to arrive at the scene of an infection or injury.

Other leukocytes such as lymphocytes, monocytes, and eosinophils have important roles in the immune system but are present in lower percentages in the bloodstream. Lymphocytes are crucial for adaptive immunity, monocytes develop into macrophages which are effective at cleaning up debris and pathogens, and eosinophils are primarily involved in the response to parasitic infections and allergic reactions. However, none of these outnumber neutrophils in a typical blood sample.