Protein expression analysis by ELISA and flow cytometry: Murine CSF1 protein was detected in splenocytes isolated from wild-type C57BL/6 (+/+) mice, while human CSF1 protein was detected in homozygous double humanized B-hCSF1/hCSF1R (H/H) mice. Murine CSF1R protein was detected in blood collected from wild-type C57BL/6 (+/+) mice, while human CSF1R protein was detected in homozygous double humanized B-hCSF1/hCSF1R (H/H) mice. In vivo efficacy evaluation: Anti-human CSF1R antibodies and combination therapy of anti-mouse PD-L1 and anti-human CSF1R antibodies were effective in inhibiting MC38 tumor growth in double humanized B-hCSF1/hCSF1R mice.