Abstract: The present invention provides the in-vitro use of at least one in-vivo-target antigen of Aspergillus fumigatus for selective activation, detection and/or analysis of Aspergillus fumigatus specific CD4+ T cells in a sample comprising cells, wherein said at least one in-vivo-target antigen reveals an immune reactivity characterized by i) the in vivo existence of antigen-specific T cells comprising more than 60% memory T cells and ii) said antigen-specific T cells further comprise T cells able to produce IFN-gamma upon stimulation at a frequency between 15% and 80% and/or IL17 upon stimulation at a frequency between 5% and 30%. Said at least one in-vivo-target antigen may be selected from the group consisting of antigens Scw4, Pst1, Shm2, GliT and TpiA or fragments thereof. Also provided are a method, a composition, and a kit thereof.