Is Genes in the Mouse

Abstract

Progress in understanding suppressor T cells since the last International Congress can be summarised in the following terms. The phenomenon of suppression of this type has not been seriously challenged, and instances of suppression continue to accrue. Some are in areas of clinical relevance, such as organ transplantation (Gassel 1987). Others are in branches of immunology opened up by molecular genetics such as the new array of mycobacterial antigens (Ivanyi 1989). There have also been setbacks. For instance one of the best pointers to suppression has been dominant inheritance of unresponsiveness. MHC-controlled dominant unresponsiveness to a particular antigen never provided more than a clue that suppression might be operating, but nevertheless it served as a source of encouragement. Now it has become clear that a second major cause of such unresponsiveness operates through deletion of large segments of the T-cell-repertoire by negative selection in the thymus (McDuffie 1988). MHC molecules are powerful inducers of tolerance, and as such can delete the T-cell response not only to themselves but also to other antigens. This discovery significantly weakens the value of dominant unresponsiveness as a clue for suppression. Another setback has been in the area of suppressor epitopes.