In clinical applications, the efficacy of anti-CD20 mAbs seems to be decline after a period of months of treatments due to therapeutic resistance. Actually the explanation for this therapeutic resistance is not clear. The possible mechanisms of this resistance of B-cell NHLs against anti-CD20 mAbs therapy may be include three patterns: (I) Protection of the tumor cells from mAbs mediated depletion of B-cell lymphoma by ADCC, CDC and apoptotic stimulation (II) Inadequate binding of mAbs to the CD20 molecule and (III) Low levels of CD20 antigens on cells surface or reduce CD20 surface levels on cells.