Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

The correct answer, T lymphocytes, is appropriate due to their larger size and prominent presence of vacuoles, particularly when activated. T lymphocytes, part of the adaptive immune system, can differentiate into various subtypes such as helper T cells and cytotoxic T cells. Upon activation, they take on a larger morphology and display an increase in cytoplasmic granules and vacuoles, which are involved in their role in immune responses, such as cytotoxic action and secretion of cytokines.

In contrast, B lymphocytes, while they can also appear larger when activated, typically do not show as many vacuoles as T lymphocytes. Natural killer (NK) cells, which play a crucial role in innate immunity, are also larger than B lymphocytes but usually have fewer cytoplasmic vacuoles compared to activated T cells. Monocytes are the largest type of white blood cell and do have vacuoles, but they are classified as a type of myeloid cell rather than a lymphocyte, focusing more on phagocytic activities rather than the specific immune responses attributed to T lymphocytes.