IL-1α levels increase with acute platelet demands. (A) Initial screening for thrombopoietic humoral factors in cultured BM cells. BM cells isolated from 6-wk-old WT mice were cultured without (CTRL) or with TPO (50 ng/ml) plus stem cell factor (SCF; 50 ng/ml). After culture for 7 d, secretion of humoral factors into the culture medium was assessed using MAPs analysis. Shown are the MAPs value ratios (TPO+SCF/CTRL). Seven factors with a ratio of >2.5 were identified. LT, lymphotactin; GCP, granulocyte chemotactic protein. n = 5 experiments. (B) BM cells were collected and then cultured in the presence of IL-1α, IL-1β, IL-2, IL-3, IL-6, LT, IL-12 subunit p70, or GCP-2. Production of CD41⁺CD42b⁺ particles was evaluated in the culture media after 7-d culture. The percent value was normalized to that of medium from vehicle-treated cells. n = 5 experiments. (C and D) Platelet counts, MPV values, and serum IL-1α, IL-1β, IL-6, and TPO levels after administration of anti-CD42b antibody (R300) (C) or thioglycolate (D). n = 5–8 animals in each group. (E) MK dynamics and platelet counts after thioglycolate-induced peritoneal inflammation in 6-wk-old CAG-eGFP mice, which were simultaneously treated with IgG or neutralizing anti–IL-1R antibody (100 µg/mouse.). n = 8 animals in each group. *, P < 0.05 versus CTRL group.