UPFRONT | News and events IMMUNITY How the immune system remembers viruses When a virus enters the body, it is picked up by cer-tain cells of the immune system. They transport the virus to the lymph nodes where they present its frag-ments, known as antigens, to CD8+ T cells responsible control of viral infections. Each of these cells carries a unique T cell receptor on the surface that can recog-nize certain antigens. How-ever, only very few T cell receptors match a given viral the antigen. To bring the infection under control and maximize the defenses against the vi-rus, these few antigen-spe-cific T cells start dividing rapidly and develop into effector T cells. These kill virus-infected host cells and then die off themselves once the infection is cleared. Some of these short-lived effector cells --according to the generally accepted the-ory --turn into memory T cells, which persist in the organism long term. In case the same pathogen enters the body again, memory T cells are already present and ready to fight the in-vader more swiftly and ef-fectively than during the first encounter. Memory cells and their origin “Prevailing scientific opin-ion says that activated T cells first become effector cells and only then gradually develop into memory cells,” says Dr. Veit Buchholz, a specialist in microbiology and working group leader at the Institute for Medical Microbiology, Immunology and Hygiene at TUM. “In our view, however, that isn’t the case. It would mean that the more effector cells are formed after contact with the pathogen, the more nu-merous the memory cells would become.” However, Buchholz and his colleagues observed a different course of events and have now published their results in the journal Nature Immunology. “We investigated the antivi-ral immune responses resulting from individual activated T cells in mice and traced the lineage of the ensuing memory cells using single-cell fate map-ping,” reports first author Dr. Simon Grassmann. “Based on these experiments, we were able to show that certain ‘T cell families’ descended from indi-vidual cells form up to 1000 times more ‘memory’ than others. However, these long-term dominating T cell families only contributed little to the magnitude of the initial im-mune response, which was dominated by effector cells derived from other short-er-lived T cell families.” At the level of individual cells, it therefore became evi-dent that development of effec-tor and memory cells segre-gates at a much earlier stage than previously believed: “Al-ready in the first week after the confrontation with the patho-gen, we saw major differences in the transcriptomes of the detected T cell families,” says Lorenz Mihatsch, also a first author of the study. “Normally at this time of the immune re-sponse CD8+ T cells are en-riched in molecules that help to kill virus infected cells. However, we found no indi-cation of these cytolytic molecules in the long-term dominating T cell families. Instead, they were already geared exclusively towards memory development at this early stage.” Optimization of vaccines These results could help to improve vaccine develop-ment in the future, says Veit Buchholz: “To generate an optimal immune response through vaccination, the body needs to produce as many memory cells as possi-ble. For that purpose, it is important to have a precise understanding of how indi-vidual T cells are pro-grammed.” Buchholz’s study might also prove useful in helping to recognize sooner whether a new vaccine is effective. “To determine the long-term strength of an immune response, it could be helpful to measure the number of memory precur-sors within a few days of administering a vaccine,” says Buchholz. — Technical University of Munich (TUM) FITNESS Compression garments reduce strength loss after training Regular training enhances your strength, but recovery is equally important. Elastic bandages and compression garments are widely used in sports to facilitate recovery and prevent injuries. Now, a research team from Tohoku University has determined that compression garments also reduce strength loss after strenuous exercise. Their research findings were published in the European Journal of Applied Physiology. The team, led by assistant professor János Négyesi and professor Ryoichi Nagatomi from the Graduate School of Biomedical Engineering, used a computerized dynamometer to train healthy subjects until they became fatigued. The same equipment was used to detect changes in the maximal strength and knee joint position sense straight after, 24 hours after and one week after the training. Their results revealed that using a below-knee compression garment during training compensates for fatigue effects on maximal strength im-mediately following the exercise and once 24 hours has elapsed. In other words, one can begin the next maximal intensity strength training earlier if 8 Chiropractic and Naturopathic Doctor December 2020 one has used a below-knee compression garment in the previous workout. Although compression garments reduce strength loss, their findings reaffirmed that they afford no protection against knee joint position sense errors. “Our previous studies focused only on the effects of compression gar-ments on joint position sense,” said Dr. Négyesi. “The present study found such garments to have the potential to reduce strength loss after a fatigu-ing exercise, which may help us better understand how applying a com-pression garment during exercise can decrease the risk of musculoskeletal injuries during sports activities.” The researchers believe wearing a below-knee compression garment during regular workouts is beneficial because of the mechanical support and tissue compression it provides. Looking ahead, the team aims to detect whether maximal intensity programs that last for weeks produce different outcomes than the current findings to determine the longitudinal effects of compression garments. — Tohoku University www.Cndoctor.ca
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