(a,b) Heparinized peripheral blood samples from Busulfan-conditioned mice (9 mice were hFIX negative, 6 mice were hFIX positive) and (c,d) lethally irradiation conditioned mice (6 mice were hFIX negative, 15 mice were hFIX positive) were analyzed for Hb levels (a,c) and RBC counts (b,d) in RT9-hFIX-SI-MGMT chimeras expressing various levels of hFIX. The normal ranges of RBC counts and Hb levels were depicted in the shaded areas. No significant correlation between plasma hFIX levels and RBC counts or Hb concentration has been found, according to linear regression analysis (Prism version 4; GraphPad Software). P values: 0.8790 (a), 0.4333 (b), 0.4320 (c), and 0.1769 (d), respectively.