Methods for assaying antigen-specific T-cell activation in vitro, comprising the steps of (a) providing a phagocytable particle, having a candidate antigen polypeptide tightly associated thereto, wherein the particle with the associated polypeptide has been subjected to a denaturing wash resulting in an endotoxin level low enough to not interfere with the subsequent steps; (b) providing a viable antigen-presenting cell; (c) contacting the washed particle with the antigen-presenting cell under conditions allowing phagocytosis of the particle by the antigen-presenting cell; (d) providing a T-cell sample to be assayed comprising viable T-cells; (e) contacting the T-cell sample with the antigen-presenting cell contacted with the particle under conditions allowing specific activation of T-cells in response to an antigen presented by an antigen-presenting cell; and (f) determining the degree of T-cell activation in the T-cell sample.