To determine how the expression of ClpB and DnaK is regulated in A. phagocytophilum upon infection of a mammalian and an invertebrate host, we investigated the chaperone transcript levels during infection of human promyeloblast cell line HL-60 (Figure 1(a) and (b)) and tick ISE6 cells (Figure 1(c) and (d)). The gene discussed is CLPB; the disease is infection.