The present study of the regulatory T phenotype of Sézary cells led to the discovery of the expression of GARP (LRRC32) by Sézary cells. GARP has also been shown to be overexpressed in samples from patients with acute lymphoblastic leukemia. GARP therefore appears as a diagnostic marker, for monitoring T-cell malignancies, and as a therapeutic target.
Accordingly, the present invention relates to methods for the diagnosis and treatment of T-cell malignancies.