The cellular immune responses of cattle immunized with antigens of Tritrichomonas foetus were investigated. Subcutaneous injections of antigen preparations primed bovine peripheral blood mononuclear cells (PBMC) by 30 days of immunization as demonstrated by antigen-specific proliferation and by cytokine production upon antigen challenge of PBMC. Antigen-specific T-cells derived from PBMC responded by production of interferon (IFN)-γ message detected by reverse transcriptase polymerase chain reaction, secreted IFN-γ detected by enzyme-linked immunosorbent assay, and intracellular IFN-γ detected by flow cytometry. Phenotypic analysis of PBMC responding in vitro to parasite antigen demonstrated a shift from a mixed CD4 , CD8 , γδ , to predominantly CD4 , CD8⁻, γδ⁻ phenotype in the Tf190-primed PBMC. In conclusion, systemic immunization of cattle with parasite antigen results in priming of bovine T-cells that are antigen specific and can produce an anamnestic IFN-γ response to subsequent stimulation with antigens of T. foetus.