Which surface marker is unique to natural killer cells?

Which surface marker is unique to natural killer cells?

• A. CD19
• B. CD56
• C. CD3
• D. CD14

Answer: (B)

Natural killer cells are identified in part by what they do not express and what they do express. They lack markers of other hematopoietic lineages—such as CD19 on B cells, CD3 on most T cells, and CD14 on monocytes—yet they do express CD56. CD56 is the distinctive surface marker used to identify NK cells in routine immunophenotyping (often with CD16 as well, but CD56 is the classic discriminator). So, CD56 uniquely points to natural killer cells among the listed options.

Natural killer cells are identified in part by what they do not express and what they do express. They lack markers of other hematopoietic lineages—such as CD19 on B cells, CD3 on most T cells, and CD14 on monocytes—yet they do express CD56. CD56 is the distinctive surface marker used to identify NK cells in routine immunophenotyping (often with CD16 as well, but CD56 is the classic discriminator). So, CD56 uniquely points to natural killer cells among the listed options.