An immunofluorescence test using a reagent antibody directed against the CD3 surface marker identifies which cell type in human peripheral blood?

The reagent antibody directed against the CD3 surface marker specifically targets a component of the T cell receptor complex, which is present on all mature T lymphocytes. CD3 is essential for T cell activation and signaling, making it a reliable marker for identifying T cells in human peripheral blood. When performing an immunofluorescence test with this antibody, the luminance will indicate the presence of mature T lymphocytes, as they express CD3 on their surface.

The other cell types mentioned do not express CD3. B lymphocytes, natural killer cells, and monocytes each have distinctive markers that differentiate them from T lymphocytes. B lymphocytes express CD19 and CD20, natural killer cells typically express CD56 and CD16, and monocytes are characterized by CD14 and CD16. Therefore, the presence of fluorescence in the test specifically confirms the identification of all mature T lymphocytes, validating the choice given.