BackgroundAging is accompanied by alterations in immune response which leads to increased susceptibility to infectious diseases, cancer, autoimmunity, and inflammatory disorders. This decline in immune function is termed as immunosenescence; however, the mechanisms are not fully elucidated. Experimental approaches of adaptive immunity, particularly for T cells, have been the main focus of immunosenescence research. This systematic review evaluates and discusses T cell markers implicated in immunosenescence.ObjectiveTo determine the best flow cytometry markers of circulating T cells associated with immunosenescence.MethodsWe systematically queried PubMed, MEDLINE, EBSCO, and BVS databases for original articles focused on two age groups of healthy humans: 18–44 (young adults) and >60 (older adults) years. In accordance with the Cochrane methodology, we synthesized data through qualitative descriptions and quantitative random effects meta-analysis due to extensive heterogeneity.ResultsA total of 36 studies conducted in the last 20 years were included for the qualitative analysis and four out of these studies were used to perform the meta-analysis. A significant decrease in naïve T cell subset was observed in older adults compared to young adults. Primary markers used to identify senescent cells were loss of CD28 and increased expression of CD57 and KLRG1 in terminally-differentiated memory T cell subset in older adults. Moreover, we observed an increase in proinflammatory cytokines and decrease in telomere length in old adult T cells. It was not possible to perform quantitative synthesis on cell markers, cytokines, and telomere length because of the significant variations between the groups, which is attributed to differences in protocols and unreported measurements, thus generating a high risk of bias.ConclusionsHeterogeneity among studies in terms of data report, measurement techniques and high risk of bias were major impediments for performing a robust statistical analysis that could aid the identification of eligible flow cytometry markers of immunosenescence phenotype in T cells.

Monitoring literature on the broad spectrum of the human immune response to SARS-CoV-2 is important to understand the mechanisms and progression of COVID-19. The present study undertakes a scoping review of the literature on human immune response to SARS-CoV-2 to determine the characteristics of innate and adaptive responses, as well as biomarkers and cells that play a role in the development of the infection. We searched papers in MEDLINE/PUBMED and EMBASE databases published since December 1st 2019 to to April 9th 2020 from which we selected 56 for this study. We found that the immune response is characterized by high levels of acute phase reactants, neutrophilia, low levels of NKs and eosinophils, lymphopenia, cytokine storm syndrome, exhausted T cells, impaired cytotoxic response, inadequate helper response and production of specific antibodies; concluding that immune dysregulation correlates with disease severity and high mortality.Respuesta inmune humana al SARS-CoV-2: ¿Qué se conoce? Una scoping review. ResumenEl seguimiento de la literatura sobre la respuesta inmune humana al SARS-CoV-2 es importante para comprender los mecanismos y la progresión de COVID-19. En el presente estudio se realizó un Scoping Review de la literatura sobre la respuesta inmune humana al SARS-CoV-2 para determinar las características de la respuesta inmune innata y adaptativa, así como biomarcadores y células que juegan un papel en el desarrollo de la infección. Buscamos artículos en las bases de datos MEDLINE / PUBMED y EMBASE publicados desde el 1 de diciembre de 2019 hasta el 9 de abril de 2020, de los cuales seleccionamos 56 publicaciones para este estudio. Encontramos que la respuesta inmune se caracteriza por altos niveles de reactantes de fase aguda, neutrofilia, bajos niveles de NKs y eosinófilos, linfopenia, síndrome de tormenta de citoquinas, linfocitos T agotados, respuesta citotóxica alterada, respuesta T helper inadecuada y producción de anticuerpos específicos. En conclusión, el desequilibrio inmune se correlaciona con la severidad y la mortalidad de la enfermedad.

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