Helper T-cell type 1 or type 2 function of xeno-MHC-restricted T-cell clones in a direct xenoantigen recognition.

There have been several reports that xeno-MHC-restricted T-cells have a cytotoxic function through a direct xenoantigen recognition, but yet no report that they have a helper function. Previously we showed that both xeno-MHC-restricted CD4(+) and CD8(+) T-cells recognized xenoantigens directly in a mouse anti-rat combination. In this study, we investigated whether or not xeno-MHC-restricted T-cells had a helper function. Mouse T-cell clones recognizing rat antigens directly were derived from T-cell lines using the limiting dilution method. Phenotype, cytotoxic activity and cytokine production of these clones were analyzed by flow cytometry, 51Cr release assay and ELISA, respectively. Rat-MHC class I-restricted mouse CD8(+) T-cell clones showed a specific cytotoxic activity against rat antigens. One CD4(+) clone produced IL-4 and IL-10, and the other CD4(+) clone produced not T-helper (Th) 2 cytokine but TNF-alpha. Our results suggested that xeno-MHC class I-restricted CD8(+) T-cells should have a cytotoxic function, and xeno-MHC class II-restricted CD4(+) T-cells should have either Th1 or Th2 function.