Background: Aspergillus fumigatus (A. fumigatus) is an opportunistic fungus that causes invasive aspergillosis. Determining the immune changes during A. fumigatus infection and the factors leading to such changes clearly will make it possible to prevent the spread of the infection and to provide new strategies in the treatment of infection. Thus, the present study aims at determining the changes of lymphocyte surface antigens which develop during A. fumigatus infection and the role of cytokines in immune response. Methodology: The expression of the surface antigens of lymphocytes was analysed by flow cytometry and the cytokine levels were determined by ELISA in a mouse model of aspergillosis. Results: It was observed that in mice infected by A. fumigatus the percentage of CD19+ B cells and the levels of IL-4 and IL-10 increased when compared to those in noninfected mice cells. Conclusions: These results suggest that Th2 type cytokines are important in the pathogenesis of A. fumigatus infection. Humoral immunity is considered to be effective during A. fumigatus infection because of the increase in Th2 type response.