Which type of white blood cell can appear atypical or reactive on a Wright-stained smear?

The lymphocyte is the type of white blood cell that can appear atypical or reactive on a Wright-stained smear. Atypical lymphocytes often present in response to viral infections or certain other stimuli, such as chronic immune responses. These cells may show variations in size, increased cytoplasmic volume, and irregular nuclear shapes compared to characteristic lymphocytes.

In a clinical context, observing atypical lymphocytes can indicate an active immune response, particularly in the presence of infections like infectious mononucleosis. This reactive appearance is a signal for further investigation and interpretation by a laboratory professional.

Granulocytes, monocytes, and eosinophils have distinct staining characteristics and more consistent morphology, which generally do not exhibit the same reactive changes as lymphocytes do during immune challenges. While they can demonstrate changes under certain conditions, they are less commonly described as atypical in the same manner as lymphocytes. This makes the lymphocyte the most appropriate choice in the context of this question.