An in-vitro method of activating T cells is disclosed. The method comprises incubating T cells with pathogenic cells in the presence of a multimeric peptide comprising at least two peptide monomers linked to one another, each of the at least two peptide monomers comprising at least 6 consecutive amino acids from the amino acid sequence as set forth in SEQ ID NO: 1, wherein the at least two peptide monomers are each no longer than 30 amino acids, wherein the multimeric peptide is capable of reducing binding of PLIF to human leukocytes under conditions which allow expansion of the T cells.
