Objective To evaluate the expression and function activity of P-glycoprotein （P-gp） in human mononuclear cells （MNCs） in vitro transfected by multidrug resistance-1（MDR1） mRNA. Methods Two MDR1 cDNA vectors

pT7TS

M

DR1 and pGEM5Zf（+）

M

DR1

were constructed and transcripted in vitro. Vector pGEM5Zf（+）

M

DR1 only contained the coding region of mdr1 cDNA

and pT7TS

M

DR1 also included Xeponus β-globin 5’ and 3’ untranslated region. MNCs were prepared from peripheral blood of parvicellular lung cancer patient. The two human mdr1 mRNAs were then transferred into human MNCs in vitro by DOTAP. And the expression efficiency and pump function of P-gp were measured with flow cytometry. Results Expression of P-gp significantly elevated in both transferred cells compared with untransferred cells （P

<

0.01）. And pT7TS

M

DR1 showed higher capability in elevating the expression of P-gp than pGEM5Zf（+）

M

DR1 （P

<

0.01）. The P-gp function was elevated in both pT7TS

M

DR1 and pGEM5Zf（+）

M

DR1 groups. The survival ratio of MNCs in erythrocyte-lysis-solution （ELS

86.07%） and lymphocyte-isolation-solution （LIS

83.67%） had no significant difference. The CD34+ cells content of the MNCs used for transfection was 2.65% and 1.01% in ELS and LIS group

respectively （P

<

0.01）.Conclusions It is a feasible approach to improve P-gp expression in human MNCs by transfection of MDR-1 mRNA. And the ELS may be more suitable for purifing MNCs for mRNA transfection than LIS.