CD158k and PD-1 expressions define heterogeneous subtypes of Sezary syndrome

Sezary syndrome (SS) is a rare leukemic form of cutaneous T-cell lymphoma. Diagnosis mainly depends on flow cytometry, but results are not specific enough to be unequivocal. The difficulty in defining a single marker that could characterize Sezary cells may be the consequence of different pathological subtypes. In this study, we used multivariate flow cytometry analyses. We chose to investigate the expression of classical CD3, CD4, CD7, and CD26 and the new association of 2 markers CD158k and PD-1. We performed lymphocyte computational phenotypic analyses during diagnosis and follow-up of patients with SS to define new SS classes and improve the sensitivity of the diagnosis and the follow-up flow cytometry method. Three classes of SS, defined by different immunophenotypic profiles, CD158k(+) SS, CD158k(−)PD-1(+) SS, CD158k and PD-1 double-negative SS, showed different CD8(+) and B-cell environments. Such a study could help to diagnose and define biological markers of susceptibility/resistance to treatment, including immunotherapy.