Immunity: research reveals why people have immune memory?

June 7, 2019 / BIOON / - natural killer cells are part of the innate immune system Their role is to detect infected cells and destroy them When an infection is detected, a small number of the most effective killer cells are identified and selectively expanded - as a team at the Technical University of Munich (tum) has now demonstrated for the first time This may represent a simple and ancient form of immune memory More than half of the world's population is infected with cytomegalovirus (CMV), which will live in the body for a lifetime Usually, these infections do not produce any symptoms Although it can cause serious diseases in people with weak immune system, natural killer cells (nks) can effectively control the virus together with T cells Nks have surface molecules that recognize CMV infected cells, such as mouse receptor Ly49H It is known that nks carrying this receptor (Ly49H nks) are particularly effective in destroying CMV infected cells Photo source: the number of immune receptors determines the effect Dr Veit Buchholz, head of the research team of the Institute of medical microbiology, immunology and hygiene, University of technology, Munich, and his colleague Dr Simon Grassmann set out to determine what happened to these Ly49H nks during cytomegalovirus infection To do this, they tracked the immune response of a single Ly49H nks in CMV infected mice They found that replication of a single Ly49H nks was very different This change is related to different surface expression levels of Ly49H itself The cells with high Ly49H expression expanded more and could fight CMV more effectively This trait seems to be heritable, and the offspring of NK are similar to their "mother" cells at Ly49H receptor level No inheritance of such quantitative traits has been observed in nks before "What's really interesting is that even after the peak of immune response, a high number of lys49h expressing killer cells can still be detected," said Grassmann "He went on to explain that this is an important indication of the existence of a simple nks based immune memory Immune memory works only when there is a selective mechanism that can reproduce and retain the most effective cells against infection "We found that in the evolution of the ancient innate immune system, the number of receptors alone is enough to drive selection at a simple level," Buchholz said "This finding may also be significant for humans, as human nks have an equivalent receptor that plays an important role in CMV infection Using a bar code of fluorescent proteins, the researchers first identified and tracked 30 human nks and their offspring Next, researchers would like to know how nks transmit information about the number of receptors to future generations Nks is considered as a possible alternative to T cell immunotherapy for infection and tumor diseases Reference: Simon Grassmann et al, distinct surface expression of activating receiver Ly49H drives differential expansion of NK cell clones upon murine cytomegalovirus infection, immunity (2019) Doi: 10.1016/j.immuni.2019.04.015