Expression and Characterization of a Divalent Chimeric Anti‐Human CD3 Single Chain Antibody

Murine anti‐CD3 monoclonal antibodies (MoAbs) are used in clinical practice for immunosuppression. However, there are two major drawbacks to this treatment: the associated cytokine release syndrome and human anti‐mouse antibody response. To overcome these side‐effects, the authors generated a chimeric anti‐human CD3 single chain antibody, scUCHT1. It is an IgM variant of UCHT1, a mouse IgG1 MoAb directed against human CD3. scUCHT1 consists of the light and heavy variable chain binding domains of UCHT1 and a human IgM Fc region (CH2 to CH4). scUCHT1 was produced by COS‐7 and SP2/0 transfectants, and mainly assembled in a dimeric form. It retained the binding specificity and affinity of the parental MoAb UCHT1. In contrast to UCHT1, scUCHT1 did not induce T‐cell proliferation and cytokine release (TNF‐α and IFN‐γ) in in vitro assays. These results suggest that the engineered chimeric anti‐CD3 single chain antibody (scUCHT1) may be useful in clinical immunosuppressive treatment.