The invention relates to a method for producing polyclonal antibodies against an antigenic target protein which comprises inducing an immune response in a host by applying an immunogenic composition comprising membrane vesicles incorporating said antigenic target protein to said host and obtaining antibodies against said target protein from the host's serum. A more specific embodiment of this method comprises at least the following steps: a) synthesizing the target protein my means of an in vitro translation reaction in a reaction medium comprising a nucleic acid template coding for the target protein and a cell lysate which contains membrane vesicles; b) separating membrane vesicles comprising the synthesized target protein from the medium; c) providing the membrane vesicles comprising the synthesized target protein in a physiologically compatible medium; d) applying the membrane vesicles of step c) to a host; e) testing a serum sample of the host for a specific immune response against said target protein; and f) obtaining specific antibodies against said target protein from the serum of a host exhibiting a specific immune response against said target protein.