Monocytes promote survival of malignant T cells. (A-E) Cells were stained with annexin V and 7-AAD and viability of Sézary cells (SCs) was reported. PBMCs were either mock or CD14 depleted (A-C) and cultured for approximately 7 days before staining. Malignant T cells were identified by staining for the appropriate T-cell receptor (TCR) Vβ chain. For samples in which TCR Vβ use was unknown, malignant CD4⁺ T cells were identified by the aberrant down-regulation of CD7. The data shown in panel B represent the mean ± SD of 4 independent samples. (C) CD14-depleted samples were supplemented with either purified autologous monocytes (first 3 samples shown, indicated by “mono”) or with supernatants (ie, monocyte-conditioned media; last 7 samples shown, indicated by “Mono-CM”) derived from cultured patient-derived monocytes or with monocyte-conditioned media (mono-CM) derived from normal donor monocytes, as indicated. (D) SCs derived from PBMCs or skin from the same patient were cultured in serum-free media supplemented with autologous mono-CM and viability of CD4⁺CD7⁻ SCs was determined by annexin V and 7-AAD staining. (E) Total PBMCs (n = 6) or skin-infiltrating lymphocytes (n = 4) were cultured in serum-free (SF) conditions (■) or in SF media supplemented with 40% mono-CM (□) and viability of CD4⁺CD7⁻ malignant T cells was determined, as described for panel D.