LILRB1 ligation inhibits cytokine secretion and stimulatory capacity for memory responses. (A) Levels of cytokines in supernatants from cells cultured as indicated were analyzed by ELISA. Results are representative of 4 experiments. Similar results were obtained when LILRB1 was ligated with HCMV UL18-Fc (not shown). (B) Cell populations were cultured with graded doses of tetanus toxoid, irradiated, and used to stimulate CFSE-labeled autologous T-cell proliferation for 7 days. Proliferation was assessed by flow cytometric analysis of CFSE levels in responder CD3⁺ T cells. Results are representative of 2 experiments. (C) Cell populations were incubated with FITC-labeled 40K-dextran at either 4°C or 37°C, washed, and analyzed by flow cytometry. Results shown are the averages of 2 experiments.