Do T ''Suppressor'' Cells Exist?

T lymphocytes beloging to the CD8+ class were initially split into ''cytotoxic'' and ''suppressor'' subpopulations, the former subset being phenotypically characterized as CD8+ CD28+, and the latter as CD8+ CD11b+. We intented to ascertain whether such subpupolations were mutually exclusive, and indeed found by immunoelectonmicroscopy that one subset was CD8+ CD28+ CD11b-, whilst the other was CD8+ CD11b+ CD28-. Nevertheless, recent functional studies showed that not only the CD8+ CD28+ subset is able to trigger T-cell mediated cytotoxicity, but even the CD8+ CD28+ subset is capable of a potent cytolytic function. Therefore, the CD8+ CD11b+ subset, formerly defined ''suppressor'' as opposed to ''cytotoxic'', should now be defined ''cytotoxic'' itself, because it is capable of a cytolytic function indeed. On the other hand, since such subset was classically demonstrated to be able to ''suppress'' both B-cells differentiation and T cells proliferative responses it seems likely that such ''suppressor'' function can be well due to the cytolytic activity of such cells against the respective targets. Similarly, in fact, CD4+ cytotoxic clones were recently demonstrated to specifically induce ''suppression'' of antibody production by killing hapten-specific B-cells. Taken together, these findings prompt us to hypothesize that the term ''supressor'' lymphocyte could be avoided, because it is somehow confusing, and should no way be considered as necessarily opposed to the term ''cytotoxic''. Rather, there is now increasing evidence for the existence of a ''Th1-like'' CD8+ T subset as opposed to a ''Th2-like CD8+ T subset,and some Authors are tempted to define the latter as ''suppressor''. It should however be reminded that ''suppression'' is a phenomenon regarding the reciprocal control of four T subsets (i.e.:Th1, Th2, ''Th1-like''CD8+,''Th2-like''CD8+), which regulate one another secondary to the differential production of cytokines by either subsets of CD4+ or CD8+T cells.