To determine whether osteopenia in trabecular regions of long bones in B. burgdorferi-infected mice was associated with changes in bone cell numbers, we measured the osteoclast number per bone surface (Oc.N/BS) in tartrate-resistant acid phosphatase (TRAP)-stained sections of right proximal tibial metaphyses and L4 vertebrae, and also osteoblast numbers per bone surface (Ob.N/BS) in trichrome-stained sections of the left proximal tibial metaphyses and L3 vertebrae (Fig. 5A and B). This evidence concerns the gene ACP5 and Osteopenia.