Immunosuppressive antilymphocyte serum: IV. Characterization of a T-cell-specific antibody that shifts T-lymphocyte subpopulations in vivo

We have characterized a biologically active antibody present in immunosuppressive but not nonimmunosuppressive antilymphocyte serum. This antibody when administered to rats induced a dose-dependent fall in the numbers of one subpopulation of T lymphocytes while leaving a second subpopulation relatively untouched. When absorption studies were performed, the active antibody was shown to be T-cell specific and could be absorbed preferentially by a subpopulation of thymus lymphocytes which were steroid resistant. The data revealed that the relevant antigen was found in highest concentration on a minority of thymus cells.