MOLECULAR AND ELECTRON MICROSCOPIC ANALYSES OF ANTIGEN PRESENTATION BY TOXOPLASMA-INFECTED CELLS

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Electron microscopic analysis of Toxoplasma gondii(T.gondii)-infected cells prepared by the combination of quick-freezing with the deep etching or freeze-substitution methods revealed that the outer membrane of T.gondii fused with some parts of the vacuolar membranes of host cells to build up channel-like structures. Work station and cytofluorometry studies detected T.gondii-derived materials in the cytoplasm of T.gondii-infected cells which strongly suggested the direct entry into cells of T.gondii antigens. Naturally processed peptides derived from T.gondii were acid extracted from T.gondii-infected cells and detected by cytotoxic T lymphocytes(CTL) derived from peripheral blood lymphocytes of a patient with chronic toxoplasmosis. This lytic activity of the CTL lines against T.gondii-infected cells pulsed with fractioned HPLC extract from xx-infected cells was restricted by HLA class I molecules. The amino acid sequence of the HLA class I molecule-bound peptide was in part consistent with the predictive algorithm of HLA class I molecule-binding peptide motifs.