Four of 21 renal transplant recipients treated with OKT3 for rejection episodes developed a second sustained (~2 weeks) depression in CD3 peripheral blood lymphocyte cell-surface-marker expression. This occurred after OKT3 therapy had ceased, subsequent to a return toward baseline CD3 levels seen before OKT3 therapy was instituted. The second decrease in CD3 T cell counts was dissociated from CD2 marker T cell counts using flow cytometry and coincided with transient cytomegaloviral infections. Three phases of immunosuppression were defined in these 4 patients: phase I (during OKT3 treatment); phase II (after treatment when CD3 counts were reconstituted); and phase III (when CD3 counts again were depressed). During phase III, serum of the 4 affected patients could transfer a blocking effect on the expression of the CD3 marker of peripheral blood T cells of 'normal' laboratory volunteers. Contained in these sera were human IgG antibodies that bound on Western blot analysis and by radioautography after immunoprecipitation to a protein band of a T cell membrane lysate with an m.w. of 23 kD. The reaction was identical to that seen with OKT3 (immunoprecipitation). Moreover, this Western blot binding could be virtually (but not completely) eliminated by multiple absorptions of the T cell membrane lysate with OKT3. By using an affinity-purified human anti-OKT3 IgG from one of the 4 patients, it was possible to immunoabsorb from phase III sera the CD3 blocking activity as well as the binding to the 23 kD protein band. A reverse immune absorption by the phase III sera with the anti-OKT3 IgG after ultracentrifugation prevented the anti-OKT3 IgG from binding to OKT3 coated plates in solid-phase radioimmunoassay. These data support the notion that autoimmune human anti-anti-id (Ab2) antibodies can occasionally be generated by treatment with OKT3, which are directed against CD3 complex epitopes similar to the ligand of OKT3.
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