The present invention relates to chimeric antigen receptors (CAR). CARs are able to redirect immune cell specificity and reactivity toward a selected target exploiting the ligand-binding domain properties. In particular, the present invention relates to a Chimeric Antigen Receptor in which extracellular ligand binding is a scFV derived from a CD19 monoclonal antibody, preferably 4G7. The present invention also relates to polynucleotides, vectors encoding said CAR and isolated cells expressing said CAR at their surface. The present invention also relates to methods for engineering immune cells expressing 4G7-CAR at their surface which confers a prolonged "activated" state on the transduced cell. The present invention is particularly useful for the treatment of B-cells lymphomas and leukemia.