Various experimental models have confirmed that graft-vs.-host virus (GVHD) does not occur in irradiation chimeras when the graft does not contain mature, immuno competent T lymphocytes, but clinical studies have shown that T cell depletion of donor marrow can be associated with a greatly increased risk of graft failure. Several inflammatory cells reach a corneal allograft by two routes—from vessels in the peripheral recipient cornea, and from vessels in the recipient iris via the aqueous humour. Different aqueous and intragraft T cell subset proportions were seen early in rejection, although a preponderance of CD+cells was found in both aqueous and graft at later times Clonal deletion of auto reactive T cells occurs; a peptide antigen was used to induce deletion of antigen-reactive thymocytes in vivo. Mice transgenic for a T cell receptor (TCR) that reacts to this peptide contain thymocytes that progress from the immature to the mature phenotype.

Administration of intraperitoneal peptide antigen of the transgenic mice results in a rapid deletion of the immature CD4+ thymocytes. Approximately 70% of human thymocytes acquired a thymocyte-restricted antigen, OKT, lost OKT antigen, and expressed reactivity with OKT and OKT. These previous two monoclonal antibodies were previously shown to describe inducer (helper) and cytotoxic/suppressor populations, respectively, in peripheral blood.