Time-course of serum EPO concentration and ERFE (Fam132b) mRNA expression after injection of heat-killed BA. Serum EPO levels (A) and ERFE mRNA expression in the bone marrow and spleen (B) were elevated by 7 days. Both serum EPO and Erfe mRNA reached a peak at 13 days and remained above baseline for 21 to 28 days. Data shown are means ± SEM and were compared for each time point to values for control mice at t = 0 (n = 6-7 per time point) by 2-tailed Student t test (***P < .001, **P < .01, *P < .05).