Impact of neutrophil-, monocyte-, and DC-conditioned medium on expression of CXCR1 on CD8⁺ T cells. (A) LPS itself reduced expression of CXCR1 on CD8⁺ T cells by a mean of 4.4% (range, –9.7% to 0.32%) (n = 15). By contrast, supernatant from LPS-stimulated neutrophils induced its subset-selective up-regulation (n = 15). Filled symbols indicate data obtained after incubation with autologous supernatant; open symbols, data obtained after incubation with allogeneic supernatant. (B) Time course of neutrophil supernatant-induced CXCR1 up-regulation. Peak up-regulation was observed after 15 minutes of incubation; thereafter, receptor re-internalization occurred (representative of n = 2). (C) Phenotypic characterization of monocytes (top panel) and immature versus mature DCs (bottom panel) assayed for their release of mediators impacting on expression of CXCR1 by CD8⁺ T cells. (D) Neither monocyte- nor DC-derived supernatants induced up-regulation of CXCR1 on CD8⁺ T cells (n = 3, each tested with supernatant derived from 2 individual donors).