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Monoclonal antibodies

Monoclonal antibodies. Polyclonal antibodies vs Monoclonal antibodies. Polyclonal antibodies : antibody preparations consist of complex different antibodies produced by many different B cell clones Monoclonal Antibody:

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Monoclonal antibodies

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  1. Monoclonal antibodies

  2. Polyclonal antibodies vs Monoclonal antibodies • Polyclonal antibodies: antibody preparations consist of complex different antibodies produced by many different B cell clones • Monoclonal Antibody: highly specific antibody produced by a single B cell clone against a single type of epitope

  3. Monoclonal antibodies (mAb or moAb) • specific antibodies that are identical because they are produced by one type of immune cell (a single parent cell). • Antibodies produced from a single clone of B cells. • Produced by fusing a B cell secreting the desired antibody with a myeloma cell (Malignant plasma cell) capable of growing indefinitely in tissue culture (immortal) = (Hybridoma cell) • Monoclonal antibodies all have identical antigen-binding sites. i.e. they all bind to the same epitope with the same affinity. • They are all of the same antibody class (isotype).

  4. Hybridoma cell • are cells that have been engineered to produce a desired antibody in large amounts and low cost. • To produce monoclonal antibodies B-cells are removed from the spleen of an animal that has been immunized with the desired antigen • These B-cells are then fused with myeloma tumor cells that is immortal (can grow indefinitely in culture ) • This fusion is performed by making the cell membranes more permeable. (e.g. using PEG - polyethylene glycol) • The fused hybrid cells (hybridomas), being cancer cells, will multiply rapidly and indefinitely (Immortal) and will produce large amounts of the desired antibodies with single specificity( in HAT culture)

  5. Uses of Monoclonal Antibodies • Diagnostic uses: • Identifying CD markers of lymphocytes (leukemias and lymphomas) • Identifying MHC types (Tissue typing - HLA typing) • Identifying infectious agents antigens (bacteria- viruses) • Identifying tumor antigens • Identifying and quantifying hormones • Measuring protein and drug levels in serum

  6. 2- OKT-3 The first approved moAbs was OKT-3, which is anti CD3 Ab & used to decrease T cells in patients with acute graft rejection or T cell lymphomas 3- Anti TACAnti CD25(Anti I- 2R a) Decrease T lymphocytes 4- Rituximab is a humanized chimeric monoclonal antibody that targets the CD20 on B-cells thatis expressed on 90% of B-cell lymphomas

  7. 5- Trastuzumab acts on HER2/neu receptor, which is overexpressed in breast cancer cells & reduce breast cancer by 50% during the first year. 6- Omalizumab: Anti IgE Mab used in treatment of type I hypersensitivity

  8. Humanized Chimeric moAbs • Mouse mAbs: • mouse mAbs with excellent specificity produced from mouse using hydridoma technology & used in humans • But mouse proteins(100%) can be recognized as foreign and can lead to immune respone in 30-50% • (human anti mouse antibody) (HAMA response) • by recombinant DNA technology: we recombine the • human DNA constant regions from human B cell with the mouse DNA variable regions from mouse B cell. • specificity unchanged but ( 75% human & 25% mouse) • we decreased the amount of mouse protein that is recognized as foreign and lead to immune response (HAMA response)

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