The problem we addressed was: how do receptors on NK cells interact with their partners, including HLA molecules, on other cells and how can this be exploited to combat disease? This is important for society as it impacts on a number of diseases, including: Haemopoietic stem cell (bone marrow) transplantation, infection, pre-eclampsia and pregnancy disorders, cancer.
To explore this we had three main objectives.
First, we studied how variation in the receptors influences viral infection and disease course. The receptors are highly variable between individuals in their gene number, DNA sequences and expression. In order to track this extreme variation we first developed methods to determine KIR gene number in different populations, including European and African populations. Initially we developed a novel KIR typing method called QKAT that allowed us to contribute to typing populations word-wide. Further to this we developed methods to obtain full DNA sequences and arrangement of KIR genes along the chromosome. To facilitate this we visited the laboratory of Dr. Paul Norman at the University of Colorado Anschutz Medical Campus as he pioneered high-throughput state-of-the art sequencing methods to obtain this kind of data to high resolution.
With sequences in hand we could question which influenced the course of disease by comparing by various methods the KIR gene sequences of large numbers of those affected with matched normal controls. In this way we obtained evidence for the influence of KIR on Asthma, Malaria, pre-eclampsia, infection with viruses as well as in stem cell transplantation to treat leukemia. We also identified immune genes relevant to Crohn’s disease. A key finding was insight into the way KIR not only on NK cells, but also on other killer cells called T cells, to promote control of infection of viruses such as those relevant to for AIDS as well as liver disease.
Next to the KIR genes on chromosome 19 is a set of related genes encoding LILR proteins. During the course of our project we also documented variation and arrangement of these genes as well as ways in which they modulated immunity.
Second, we investigated the mechanisms viruses use to evade immune recognition. To approach this we explored interaction of human cytomegalovirus (HCMV) with KIR receptors. We showed that this common human virus alters protein molecules at the cell surface to mitigate against recognition by NK cells, through KIRs. Collaborative work with a group in Cardiff continued to demonstrate in other ways how HCMV modulates NK cell activation. Given we had evidence that certain viruses interact with some of the receptors in order to evade immune recognition we attempted to identify the mechanisms for this. One approach was to examine small proteins (peptides) from viruses as well as in reproduction that influence cell surface protein interaction with KIR receptors. Since as expressed above, we obtained genetic evidence, with Ashley Moffett’s group, that susceptibility of pregnant women to pre-eclampsia is influenced by various receptors on NK cells interacting with HLA molecules we searched for peptides produced by placental tissues that may be involved.
Third, we identified novel partners for NK receptors. One KIR that we studied, KIR3DL3, did not fit the normal paradigm as it did not appear to interact with any of the classic HLA molecules. An antibody to KIR3DL3 protein, raised in our laboratory, was used to see in which tissues KIR3DL3 was expressed and to probe what molecules it interacted with. We found that KIR3DL3 was present on a small specific set of cells, particularly in the gut ( and CD8 T cells) rather than on NK cells in circulation. Rather than HLA proteins it interacted with a molecule called HHLA2, implicating it as a potential target for cancer immunotherapy.
Finally, we promoted our science to the public at Cambridge Science Festival events, and we produced a JoVE video article to share our novel methodology with the scientific community.
