Effect of systemic LPS on circulating platelet counts in wild-type and TLR4^def mice. Wild-type and TLR4^def mice were untreated or treated with LPS for 30 minutes or for 4 hours. At these times, samples of blood were drawn by cardiac puncture to assess the number of circulating platelets (see “Materials and methods”). Data are expressed as the arithmetic mean ± SEM from 5 to 8 mice in each group. ^*P < .01 versus untreated wild-type mice.