The immune system has a bunch of different immune cells that are employed to help mediate response to invading pathogens. A major cell type includes CD8+ or cytotoxic T cells which eliminate infected cells. Interestingly much is known how these cells function, but it is unclear how these cells evolve over a human lifespan.
Researchers in Australia have recently published a report in Nature Immunology examining cytotoxic T cells in various age groups to see how age affects immune cells when infected with an influenza virus. The different groups included newborns, children in school, adults, and older adults (60+ years). The researchers from the Peter Doherty Institute for Infection and Immunity and UNSW Syndey were led by Dr. Katherine Kedzierska and Dr. Fabio Luciani. The team found that cytotoxic T cell response was similar in newborns and older adults (60+ years). This is a very interesting finding because it is expected that as we age, immune cells should become more exhausted and non-functional. This would parallel the idea that as we get older, we are more susceptible to disease. Due to this unexpected finding, Kedierska, Lucani, and colleagues took a closer look at the cell responses to influenza virus.
Kedierska, Luciani, and colleagues demonstrated that even though the T cells were present and responded similarly, they were a suboptimal cell-type compared to T cells in adults with a more effective function. The team used new machine learning techniques to determine how influenza-virus killer T cells develop over a lifetime. Cytotoxic T cells in older adults had a lower ability to recognize the influenza virus. Although the cells can detect infection and kill, the cells are less efficient and cannot kill as many infected cells as in younger adults. Additionally, researchers conclude that cytotoxic T cells become stronger as we get older, but at a certain point we lose these effective T cells.
Researchers also found that the gene signature or the genes expressed in the older adult T cells were similar to the T cell gene expression found in newborns. This further demonstrates a naïve T cell phenotype less experienced to fight infection over 60 years old. It is still unclear why T cells in people over 60 years old have fewer T cells that are similar to T cells in newborns. However, the evolution of cytotoxic T cells in humans has not been reported before and this could have major implications in our healthcare system.
The evolution of T cells over a lifespan contributes greatly to the field of vaccinology and provides opportunities to generate vaccines that better equip older adults. The report indicates that if T cells are boosted or expanded through vaccination early in life, then effective cytotoxic T cells could be maintained through old age. This research is pivotal in the aging research community because it has major implications in our understanding of aged immunity. It also demonstrates that vaccines should be developed or tailored to specific age groups to optimize the immune response in patients.
Report, Nature Immunology, Peter Doherty Institute for Infection and Immunity, UNSW, Katherine Kedzierska, Fabio Luciani
