Fig. 7.

Enhanced CEACAM1 expression is functional and inhibits NK killing activity. a Plots show the CEACAM1 expression profile on gated peripheral blood NK cells. Samples were derived either from healthy donors or melanoma patients, as indicated in the figure. b Peripheral blood lymphocytes were tested for natural killing activity against NK-sensitive 221 cells. Target cells were either mock transfected (221/Mock, black bars) or stable transfected with CEACAM1 cDNA (221/CEACAM1, gray bars). Effector-to-target ratio was 50-to-1. Y-axis denotes the percent of specific lysis of target cells. This figure shows a representative experiment out of three performed. *P value <0.05. c Peripheral blood lymphocytes derived from a healthy donor were cultured either in culture medium or in serum. Serum was derived either from an allogeneic healthy donor or from melanoma patients with either low or high percentage of CEACAM1-positive lymphocytes, as indicated in the figure. Peripheral blood lymphocytes from four different donors were tested, each in three different sera samples from each category. This figure shows the staining results of gated lymphocytes of a representative experiment