The invention relates to a method for the preparation of efficient antigen-presenting human .gamma..delta. T cells, to the .gamma..delta. T cellsprepared by such a method, and to their use in immunotherapy, vaccination,vaccine development and diagnostics. Similar to dendritic cells (DCs) inpotency and efficacy, these human .gamma..delta. T cells process antigens andpresent antigenic peptides to .alpha..beta. T cells and induce antigen-specific responses (proliferation and differentiation) in naïve .alpha..beta.T cells. .gamma..delta. T cells are easily purified from peripheral blood,acquire "maturation" status (expression of essential adhesion, co-stimulatoryand major histocompatibility complex molecules) within 1 day of in vitroculture under stimulation and induce strong primary and secondary T helpercell and cytotoxic T cell responses. The .gamma..delta. T cells may be used ina method of treatment of tumors or chronic or recurrent infectious diseases,in identification of novel tumor or pathogen-derived antigens, and in thediagnosis of the immune competence of a patient.
