HuM291, a humanized anti-CD3 antibody, is immunosuppressive to T cells while exhibiting reduced mitogenicity in vitro

Transplantation. 1999 Aug 27;68(4):563-71. doi: 10.1097/00007890-199908270-00020.


Background: OKT3, a mouse monoclonal antibody (Ab) specific for the human CD3 complex on T cells, is a potent immunosuppressive agent used for the treatment of acute allograft rejection. The utility of the drug has been limited by a neutralizing anti-mouse Ab response and adverse side effects resulting from T cell activation and systemic cytokine release. T cell activation is caused by OKT3-mediated cross-linking of T cells and Fc receptor-bearing cells. Studies in the mouse model have shown that global T cell activation is not necessary for immunosuppression, as Fc receptor-nonbinding anti-CD3 Abs can suppress graft rejection in the absence of the activation effects seen with Fc receptor-binding Abs. Thus, a humanized anti-CD3 antibody with a low affinity for Fc receptors might improve immunosuppressive therapy by reducing the side effects associated with OKT3.

Methods: We developed a mouse monoclonal Ab, M291, which competes with OKT3 for binding to T cells. Humanized, complementary-determining region-grafted versions of M291 featuring various Fc were engineered, including a previously described IgG2 mutant deficient in Fc receptor binding (HuM291).

Results: Compared with OKT3 and HuM291-IgG1, HuM291 was significantly less mitogenic to T cells in vitro and induced the release of much lower levels of the cytokines tumor necrosis factor-alpha, interferon-gamma, and interleukin-10. Despite this reduction in T cell activation, HuM291 retained the ability to modulate the CD3 complex and inhibit the mixed lymphocyte reaction.

Conclusions: When evaluated in vivo, HuM291 may be an immunosuppressive agent associated with less of the acute toxicity and immunogenicity seen with OKT3 therapy.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Monoclonal / adverse effects
  • Antibodies, Monoclonal / genetics
  • Antibodies, Monoclonal / pharmacology*
  • Antibody Affinity
  • Antibody Specificity
  • Antilymphocyte Serum / adverse effects
  • Antilymphocyte Serum / genetics
  • Antilymphocyte Serum / pharmacology*
  • CD3 Complex*
  • Cytokines / biosynthesis
  • DNA, Complementary / genetics
  • Drug Design
  • Humans
  • Immunoglobulin Variable Region / genetics
  • Immunosuppressive Agents / pharmacology*
  • In Vitro Techniques
  • Lymphocyte Activation
  • Lymphocyte Culture Test, Mixed
  • Mice
  • Mitogens / pharmacology
  • Molecular Sequence Data
  • Muromonab-CD3 / adverse effects
  • Muromonab-CD3 / pharmacology
  • Protein Engineering
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / immunology
  • Recombinant Fusion Proteins / pharmacology
  • T-Lymphocytes / cytology
  • T-Lymphocytes / immunology*


  • Antibodies, Monoclonal
  • Antilymphocyte Serum
  • CD3 Complex
  • Cytokines
  • DNA, Complementary
  • Immunoglobulin Variable Region
  • Immunosuppressive Agents
  • Mitogens
  • Muromonab-CD3
  • Recombinant Fusion Proteins