Understanding and manipulating Antibody Dependent Cell Cytotoxicity (ADCC) by human Natural Killer (NK) cells

Biologists have given names to nearly all the different protein molecules that mediate communication between human cells. Now, the audacious goal of contemporary cell biology is to understand how the billion proteins in a live cell allow them to move, multiply, contribute to a brain or defend us against viruses and bacteria. Imaging where and when proteins interact with each other has a major role to play at this frontier. Recent imaging of just a few types of proteins has already led to important new concepts in how immune cells communicate with each other and how they recognize signs of disease. High-resolution microscope images of immune cells contacting other cells have revealed temporary membrane structures, often called immune synapses, similar to the synapses that nerve cells make with one another for communication. Proteins commonly segregate into specific regions at the contacts between cells, and exploring how such changing arrangements of proteins occur and how they control immune cell communication is the new science opened up by the immune synapse concept. Over the last decade the use of antibodies has revolutionised the treatment of severe human diseases, such as non hodgkins lymphoma (NHL) and rheumatoid arthritis (RA). One way that these antibodies work is by triggering Natural Killer cells to directly kill diseased target cells. Crucially, nobody has yet determined what happens at immune synapses when antibodies trigger killing of diseased cells. Here, we plan to use state-of-the-art technologies to image immune synapses during antibody-medaited killing with a view to learning how to best optimise antibodies for this function. We will apply the understanding gained from these basic studies to the rational design of modified antibodies for optimal efficiency in a range of disease treatments.

We aim to characterise the NK cell immune synapse (IS) during antibody dependent cellular cytotoxicity (ADCC) with a view to determining the key properties and regions on the target antigens or effector cells that promote optimal cell killing. Using antibodies and model systems developed at MedImmune, the effects of antibody affinity, receptor density and effector function will be used to determine the effects of antibody engineering on ADCC. Using state-of-the-art confocal microscopy within Prof D. Davis group (Imperial College), the spatial relationship and segregation of proteins at the submicrometer scale within the activating IS will be determined during ADCC and compared for the different antibodies and model systems developed by MedImmune. Specifically, we propose to:

1. Determine, for the first time, the supramolecular organisation of the NK cell IS during ADCC.
2. Determine how antibody affinity and ligand density relates to NK cell effector functions, including cytotoxicity and cytokine release, and how these correlate with changes within the supramolecular organisation of the IS.
3. Determine how the location of epitope and size of antibody relates to effector functions and the supramolecular organisation of the IS.

The overarching aim will then be to apply the understanding gained from these basic studies to the rational design of modified antibodies for optimal efficiency in ADCC.