ABSTRACT
For construction of anti-CD3 human/murine chimeric antibody genes, a selective first-strand cDNA synthesis from mRNA or RNA of murine McAb HIT3a was performed using murine Ig constant region primers, and then cDNA of heavy and light chain variable domains of murine immunoglobulin were amplified by PCR using a set of degenerated oligonucleotide primers. Using these cDNA fragments as probes, the L and H chain V region exons encoding the murine McAb anti-CD3 were isolated from the gene library of HIT3a DNA and inserted into mammalian expression vectors containing the human ? and yl constant region exons for construction of human/murine chimeric antibody genes.
ABSTRACT
Exons encoding the variable regions of the light and heavy chain of the murine McAb HIT3a against CD3 antigen were isolated from HIT3a gene library and inserted into mammalian expression vectors containing the human K and y1 region exons. The chimeric genes were transfected into murine SP2/0 hybridoma cells by Lipofectin. Antibody levels of culture supernatants from transfectomas ranged 21~32 ?g/ml. The chimeric antibodies bound specifically to human T cells and competed effectivelly with the parental anti-CD3 murine McAb for binding to CD3 antigen on human T cells. The ability to promote antibody-dependent cell-mediated cytolysis was significantly enhanced with the chimeric antibodies as compared with anti-CD3 murine McAb. The mitogenic activity of human T cells can be suppressed and enhanced by the anti-CD3 chimeric antibodies. The cytotoxicity to tumor cells and proliferation of human T cells mediated by the anti-CD3 chimeric antibodies were much higher than IL-2 alone. Chimeric HIT3a antibody is a clinically relevant, genetically engineering antibody with potential use in treatment of graft-versus-host disease in tranplantation, autoimmune diseases and some tumors.