Characterization of human cytotoxic T lymphocyte-associated antigen 4-immunoglobulin (hCTLA4Ig) expressed in transgenic rice cell suspension cultures

The avidity for CD80Ig/CD86Ig and the in vitro immunosuppressive effect of recombinant human cytotoxic T lymphocyte-associated antigen 4-immunoglobulin, produced by transgenic rice cell suspension cultures (hCTLA4Ig^P) with CHO-derived recombinant hCTLA4Ig (hCTLA4Ig^M), were measured. Surface plasmon resonance (SPR) was used for kinetic binding analysis: hCTLA4Ig^P and hCTLA4Ig^M had higher avidity for CD80Ig/CD86Ig than for CD28Ig, and the avidity for CD80Ig/CD86Ig was similar. hCTLA4Ig^P and hCTLA4Ig^M had similar in vitro immunosuppressive activity against the expression of T cell-derived cytokines, such as IL-2, IL-4, and IFN-γ, but did not suppress the expression of macrophage-derived cytokines, including TNF-α and IL-1β, as well as NO. Thus the immunosuppressive mechanism of hCTLA4Ig^P is also T cell-specific and it could therefore be used as an immunosuppressive agent with an equivalent potency to that of hCTLA4Ig^M.