BY55/CD160 cannot be considered a cytotoxic marker in cytomegalovirus‐specific human CD8 + T cells

Summary CD160/BY55 is a glucosyl‐phosphatidylinositol (GPI)‐anchored cell membrane receptor that is expressed primarily in natural killer (NK) cells. Its presence in CD8 + T lymphocytes is considered to be a marker of cytotoxic activity, although there are few data in this regard. In the present work, we analysed the expression of CD160 in subpopulations of cytomegalovirus (CMV)‐specific CD8 + T cells. Subpopulations were defined by CD28 and CD57 expression and exhibited varying degrees of differentiation and cytotoxic potential, as evaluated by the expression of perforin, interferon (IFN)‐γ and interleukin (IL)‐7Rα/CD127. We included subjects with different intensities of anti‐viral immune response. Results showed that the terminally differentiated CD28 –  CD57 + subset displaying the highest level of perforin expressed CD160 at a level similar to that of memory CD28 +  CD57 – perforin – cells. A comparison of the expression of perforin in CD160 + cells versus CD160 – cells showed that expression was significantly higher in the absence of CD160. Interestingly, the CMV‐specific CD8 + T cell subset from a patient with ongoing CMV reactivation did not begin to express CD160 until day +92 of the follow‐up period. Taken together, our data show that CD160 cannot be considered a cytotoxic marker in CMV‐specific CD8 + T cells.