Figure 3. Utility of PD-1 in subtle MF/SS cases.

A, B, C and D each depict a case in which PD-1 provided clear visual separation between Sezary cells (red [emphasized in D]) and normal CD4+ T cells (green) while alterations of the remaining antigens were few and subtle, including normal CD7 expression. C and D depict example cases in which gating with the baseline panel without PD-1 in a blinded fashion (shown in the top rows) resulted in more inaccurate Sezary cell identification and enumeration compared to when PD-1 was included and used for gating (shown in the bottom rows), which was confirmed with TCR Vβ analysis (right most histograms). The sizes (percentage of total white cells) of the gated populations (red) in each case were: A: 16.9%; B: 11.4%; C top row (without PD-1): 4.87% (includes normal CD4+ T cells); C bottom row (with PD-1): 4.32% (largely pure Sezary cell population); D top row (without PD-1): 1.39% (includes normal CD4+ T cells); D bottom row (with PD-1): 2.0% (pure Sezary cell population). In each illustrated case, PCA (right most panels) demonstrated separation of the individual abnormal populations (red) from total internal normal CD4+ T cells (green). The degree of separation diminished when PD-1 was removed from the analysis (indicated by “(−)PD-1”). PD-1 in these cases provided clear, rapid and more efficient identification of the Sezary cell populations, improved separation of abnormal from normal populations, and aid in distinguishing normal T cell subsets with differential antigen expression from the truly abnormal populations.