Figure 1.

Activated platelets induce CD16 expression on CD14⁺CD16^- monocytes. (A) Representative contour plots of CD16 expression on monocytes co-cultured with or without activated platelets (right). Highly purified CD14⁺CD16^- monocytes were co-cultured for 18 h with resting platelets or ADP-activated platelets. Frequencies (%) of CD14⁺CD16⁺ monocytes were analyzed using flow cytometry (left) (n = 7). (B) Quantitative RT-PCR analysis of CD16 in monocytes co-cultured with activated platelets for the indicated times. mRNA expression of CD16 was normalized to that in monocytes incubated without platelets at the same time points (n = 5 or 6). (C) Representative contour plot of CD16 expression on monocytes co-cultured with activated platelets for 18 h or treated with the indicated cytokines for 18 h (upper panel). Frequencies (%) of CD14⁺CD16⁺ monocytes under the indicated conditions were analyzed using flow cytometry (lower panel) (n = 4). Bars show the mean ± S.E.M. *p < 0.05, **p < 0.01, and ***p < 0.001 by two-tailed paired t-test.