Circulating Adaptive Immune Cells Expressing the Gut Homing Marker α4β7 Integrin Are Decreased in COVID-19

Background Infection with the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes a wide range of symptoms including gastrointestinal manifestations, and intestinal epithelial cells are a target of the virus. However, it is unknown how the intestinal immune system contributes to systemic immune responses in coronavirus disease 2019 (COVID-19). Methods We characterized peripheral blood lymphocytes from patients with active COVID-19 and convalescent patients as well as healthy controls by flow cytometry. Results The frequency and absolute number of circulating memory T and B cells expressing the gut homing integrin alpha 4 beta 7 integrin was reduced during COVID-19, whether gastrointestinal symptoms were present or not. While total IgA-expressing B cells were increased, gut-imprinted B cells with IgA expression were stable. Conclusion COVID-19 is associated with a decrease in circulating adaptive immune cells expressing the key gut homing marker alpha 4 beta 7 suggesting that these cells are preferentially recruited to extra-intestinal tissues independently of alpha 4 beta 7 or that the systemic immune response against SARS-CoV-2 is at least numerically dominated by extraintestinal, particularly pulmonary, immune cell priming.

Automated summary

COVID-19 is associated with a decrease in circulating adaptive immune cells expressing the key gut homing marker alpha 4 beta 7, while the total number of IgA-expressing B cells is increased. This suggests that the systemic immune response against SARS-CoV-2 may be dominated by extraintestinal, particularly pulmonary, immune cell priming.