Final Report Summary - ADCC (Understanding and manipulating Antibody Dependent Cell Cytotoxicity (ADCC) by human Natural Killer (NK) cells)
In the last 15 years the use of drugs called monoclonal antibodies has revolutionised the treatment of severe human diseases including cancers and autoimmune conditions. What is still not completely understood is why some drugs are much more efficient at eradicating diseased cells than others. Therefore it is important to understand the exact mechanisms of action of these successful drugs to identify what makes them so effective.
Rituximab is a potent monoclonal antibody mediating depletion of B cells. One way by which it exerts its function is by triggering Natural Killer (NK) cells to directly kill diseased B cells coated with rituximab. Despite a high importance of the process of antibody-mediated killing in mediating efficient immune response to diseased B cells in patients not much is known about the process itself and more research was required to study what happens during antibody-mediated killing on the single cell level with a view to learning how to best optimise antibodies for this function. Therefore we sought to investigate the string of events leading from the initial coating of B cell with rituximab to the eventual killing by NK cell.
Using the state of the art microscopy techniques we studied the behaviour of human B and NK cells when co-cultured in the presence of rituximab. We showed that binding of rituximab to B cell induces changes within the cell that may then be important for the outcome of the interaction with effector NK cell. Rituximab induced modifications in the localisation of CD20 - its target protein - on the B cell surface leading to its polarisation on one side of the cell. Importantly this was specific to rituximab as another antibody targeting a similar epitope within CD20 on B cells did not induce the same type of modifications.
Importantly the process of CD20 polarisation was not a mere clustering of antigen by the antibody as other proteins such as ICAM-1 and moesin co-localised with CD20 in the same place indicating that rituximab caused a polarisation of B cells. This process of polarisation was then important for target cell killing as the cells with evident CD20 clustering were killed more efficiently by NK cells than those with homogenous distribution of the protein. This highlights a new aspect of rituximab involvement in mediating efficient ADCC. The polarisation of B cells induced by rituximab augments its therapeutic role in triggering ADCC by effector NK cells.
Many factors must be considered in the rational design of antibodies for use in ADCC and here we describe one possibly important factor that could be taken into account that involves changes to the cell surface organisation of the target cell. It may be important to consider screening potential therapeutic antibodies for their ability to trigger modification in target antigen organisation and cellular polarisation.
Rituximab is a potent monoclonal antibody mediating depletion of B cells. One way by which it exerts its function is by triggering Natural Killer (NK) cells to directly kill diseased B cells coated with rituximab. Despite a high importance of the process of antibody-mediated killing in mediating efficient immune response to diseased B cells in patients not much is known about the process itself and more research was required to study what happens during antibody-mediated killing on the single cell level with a view to learning how to best optimise antibodies for this function. Therefore we sought to investigate the string of events leading from the initial coating of B cell with rituximab to the eventual killing by NK cell.
Using the state of the art microscopy techniques we studied the behaviour of human B and NK cells when co-cultured in the presence of rituximab. We showed that binding of rituximab to B cell induces changes within the cell that may then be important for the outcome of the interaction with effector NK cell. Rituximab induced modifications in the localisation of CD20 - its target protein - on the B cell surface leading to its polarisation on one side of the cell. Importantly this was specific to rituximab as another antibody targeting a similar epitope within CD20 on B cells did not induce the same type of modifications.
Importantly the process of CD20 polarisation was not a mere clustering of antigen by the antibody as other proteins such as ICAM-1 and moesin co-localised with CD20 in the same place indicating that rituximab caused a polarisation of B cells. This process of polarisation was then important for target cell killing as the cells with evident CD20 clustering were killed more efficiently by NK cells than those with homogenous distribution of the protein. This highlights a new aspect of rituximab involvement in mediating efficient ADCC. The polarisation of B cells induced by rituximab augments its therapeutic role in triggering ADCC by effector NK cells.
Many factors must be considered in the rational design of antibodies for use in ADCC and here we describe one possibly important factor that could be taken into account that involves changes to the cell surface organisation of the target cell. It may be important to consider screening potential therapeutic antibodies for their ability to trigger modification in target antigen organisation and cellular polarisation.