Neutrophilia, lymphopenia and myeloid dysfunction: a living review of the quantitative changes to innate and adaptive immune cells which define COVID-19 pathology
Amy Codd, Stephanie Hanna, Ewoud B. Compeer, Felix Clemens Richter, Eleanor Pring, Ester Gea-Mallorquí, Mariana Borsa, Owen Moon, David Oliver Scourfield, David Ahern, Hannah Almuttaqi, Dominic S. Alonzi, Aljawharah Alrubayyi, Ghada Alsaleh, Valentina M T Bart, Vicky Batchelor, R. Bayliss, Dorothée L. Berthold, Jelena S. Bezbradica, Tehmina Bharuchq, Helene Borrmann, Mariana Borsa, Rowie Borst, Juliane Brun, Stephanie Burnell, Lorenzo Capitani, Athena Cavounidis, Lucy Chapman, Anne Chauveau, Liliana Cifuentes, Amy Codd, Ewoud B. Compeer, Clarissa Coveney, Amy Cross, Sara Danielli, Luke C. Davies, Calliope A. Dendrou, Sandra Dimonte, Ruban Rex Peter Durairaj, Lynn B. Dustin, Arthur Dyer, Ceri A. Fielding, Fabian Fischer, Awen Gallimore, Sarah A. E. Galloway, Anís N. Gammage, Ester Gea-Mallorquí, Andrew Godkin, Stephanie Hanna, Cornelia Heuberger, Sarah L. Hulin-Curtis, Fadi Issa, Emma Jones, Ruth Jones, Kristin Ladell, Sarah N. Lauder, Kate Liddiard, Petros Ligoxygakis, Fangfang Lu, Bruce J. MacLachlan, Shayda Maleki-Toyserkani, Elizabeth H. Mann, Anna M. Marzeda, R. James Matthews, Julie M. Mazet, Anita Milicic, Emma Mitchell, Owen Moon, Van Dien Nguyen, Miriam O’Hanlon, Clara Eléonore Pavillet, Dimitra Peppa, Ana Pires, Eleanor Pring, Max Quastel, Sophie Reed, Jan Rehwinkel, Niamh Richmond, Felix Clemens Richter, Alice Robinson, Patrícia R S Rodrigues, Pragati Sabberwal, Arvind Sami, Raphael Sanches Peres, Quentin J. Sattentau, Barbora Schonfeldova, David Oliver Scourfield, T. Selvakumar, Freya R Shepherd, Cariad Shorten, Anna Katharina Simon, Adrian L. Smith, Alicia Teijeira Crespo, Michael Tellier, Emily Thornton, Lion F. K. Uhl, Erinke van Grinsven, A.K. Wann, Richard Williams, Joseph D. Wilson
Abstract
Destabilization of balanced immune cell numbers and frequencies is a common feature of viral infections. This occurs due to, and further enhances, viral immune evasion and survival. Since the discovery of the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), which manifests in coronavirus disease 2019 (COVID-19), a great number of studies have described the association between this virus and pathologically increased or decreased immune cell counts. In this review, we consider the absolute and relative changes to innate and adaptive immune cell numbers, in COVID-19. In severe disease particularly, neutrophils are increased, which can lead to inflammation and tissue damage. Dysregulation of other granulocytes, basophils and eosinophils represents an unusual COVID-19 phenomenon. Contrastingly, the impact on the different types of monocytes leans more strongly to an altered phenotype, e.g. HLA-DR expression, rather than numerical changes. However, it is the adaptive immune response that bears the most profound impact of SARS-CoV-2 infection. T cell lymphopenia correlates with increased risk of intensive care unit admission and death; therefore, this parameter is particularly important for clinical decision-making. Mild and severe diseases differ in the rate of immune cell counts returning to normal levels post disease. Tracking the recovery trajectories of various immune cell counts may also have implications for long-term COVID-19 monitoring. This review represents a snapshot of our current knowledge, showing that much has been achieved in a short period of time. Alterations in counts of distinct immune cells represent an accessible metric to inform patient care decisions or predict disease outcomes.