The newly discovered cell is a dendritic cell, a type of cell that acts as a sentinel for the immune system. These specialized white blood cells continuously screen the body’s tissues for unusual activity, including the presence of bacterial pathogens, viruses, or cancer. Should they encounter something out of ordinary they trigger the body’s immune response by taking small parts of the pathogen (antigens) and displaying them on their cell surface. This then allows the killer T-cells to respond to the infection and kill the invading pathogen, a process which could be targeted for vaccine development. The now discontinued Lyme disease vaccine was itself unusual in that it targeted the bacteria in the gut of the tick in order to forestall transmission to a human host, rather than targeting the bacteria once infection has occurred. Whether these dendritic cells’ discovery can lead to a different type of vaccine remains to be seen.
Cross-Presentation in New White Blood Cell Type
These dendritic cells are unusual in that they themselves do not need to be infected in order to alert the killer T-cells to the pathogen. Most cells are only able to present antigens when infected and, thus, killer T-cells will only become activated if the cells are already infected. Working alongside A*STAR’s Singapore Immunology Network (SIgN), the scientists in Newcastle discovered the dendritic cells’ ability to generate an immune system resonse to an external antigen source in a process called cross-presentation.
Harnessing Natural Immunity for Vaccine Development
Cross-presentation has represented something of a holy grail for immunologists over recent years as they knew it must be possible but could not uncover the type of cell responsible for the process. This new dendritic cell type will likely now provide a target for research into anti-cancer vaccines, according to Dr Muzlifah Haniffa, a Wellcome Trust Intermediate Fellow and Senior Clinical Lecturer at Newcastle University. Developing such vaccines would use the body’s natural capacity for fighting infection and could help when dealing with notoriously difficult bacteria such as the Lyme disease spirochaetes.
Mouse to Human Gene-Mapping for Vaccines
As well as identifying the new type of white blood cell, the researchers also noted that dendritic cell subsets are conserved between species. Isolated dendritic cells from human blood and skin samples, as well as from mouse blood, lung and liver were tested using gene expression analysis to create a map of the gene signatures in humans and the equivalent genes in mice. This map can guide researchers when using mouse models of human disease in order to ensure that vaccines effective in animal models are likely to have a comparable effect in humans. Matthew Collin, Professor of Haematology from Newcastle University, referred to the map as a Rosetta stone for the language of mouse to humans. The researchers have made these gene signatures publicly available to help fellow scientists and it may be that a new generation Lyme disease vaccine will result from such research, especially given the increased number of cases and the potential financial benefits of producing such a vaccine.
Haniffa M et al. Human tissues contain CD141(hi) cross-presenting dendritic cells with functional homology to mouse CD103(+) nonlymphoid dendritic cells. Immunity 2012.