In flow cytometry, which markers identify helper T cells?

In flow cytometry, which markers identify helper T cells?

• A. CD3 and CD4
• B. CD3 and CD8
• C. CD19 and CD20
• D. CD8 and CD56

Answer: (A)

In flow cytometry, helper T cells are defined by being CD4-positive T cells that also express the T cell marker CD3. CD3 marks the T cell receptor complex, so all T cells are CD3+, and the helper subset is specifically CD4+. Therefore, identifying cells as CD3+ and CD4+ singles out the helper T cells. The other marker combinations point to other lineages or subsets: CD3 with CD8 marks cytotoxic T cells; CD19 and CD20 mark B cells; CD8 with CD56 would not selectively define helpers and could include other populations.

In flow cytometry, helper T cells are defined by being CD4-positive T cells that also express the T cell marker CD3. CD3 marks the T cell receptor complex, so all T cells are CD3+, and the helper subset is specifically CD4+. Therefore, identifying cells as CD3+ and CD4+ singles out the helper T cells. The other marker combinations point to other lineages or subsets: CD3 with CD8 marks cytotoxic T cells; CD19 and CD20 mark B cells; CD8 with CD56 would not selectively define helpers and could include other populations.