An experimental model of two interacting clones of T cells is described, which may be used for defining and exploring the T-cell immunoregulatory network. Mx9/9 is a CD4 clone bearing an antigen receptor recognized by the Mx9 anti-V beta 8 monoclonal antibody (MoAb). Anti-V beta 8 MoAbs activate and induce cell proliferation of this clone. Autologous clones were raised against Mx9/9 cells using the peripheral blood mononuclear (PBM) cells of the Mx9/9 clone donor (PBMjm). Some of these cloned anti-clone cells proliferated after stimulation with irradiated Mx9/9 cells, but not after stimulation with other autologous cloned T cells or heterologous PBM, suggesting that these clones recognize the T cell receptor (TCR) of the Mx9/9 cells. The proliferation of the Mx9/9 stimulated cloned anticlone cells was blocked by anti-class II MoAbs, indicating that the autoreactive clones recognize their target antigen in conjunction with HLA Class II products. The ability of clone Mx9/9 to proliferate after stimulation with anti-V beta 8 MoAb was inhibited when clone 121 cells were added to the cultures. However, clone 121 lost its suppressor function after 4 months in culture and instead gained the ability to enhance the proliferation of Mx9/9 cells in the presence of anti-V beta 8 MoAb. In contrast, clone 18 lacked suppressor activity at the early stage of the study but later acquired this function. We conclude that some autoreactive clones are not fully committed and may express more than a single function. Such cells cannot therefore be designated as 'suppressor cells', although they expressed suppressor potential at certain stages.