Depletion of circulating IgM memory B cells predicts unfavourable outcome in COVID-19
Marco Vincenzo Lenti, Nicola Aronico, Ivan Pellegrino, Emanuela Boveri, Paolo Giuffrida, Federica Borrelli de Andreis, Patrizia Morbini, Laura Vanelli, Alessandra Pasini, C. Ubezio, Federica Melazzini, Alessandro Rascaroli, Valentina Antoci, Stefania Merli, Francesco Di Terlizzi, Umberto Sabatini, Ginevra Cambiè, Annamaria Tenore, Cristina Picone, Alessandro Vanoli, Luca Arcaini, Fausto Baldanti, Marco Paulli, Gino Roberto Corazza, Antonio Di Sabatino
Abstract
Impaired immune responses have been hypothesised to be a possible trigger of unfavourable outcomes in coronavirus disease 2019 (COVID-19). We aimed to characterise IgM memory B cells in patients with COVID-19 admitted to an internal medicine ward in Northern Italy. Overall, 66 COVID-19 patients (mean age 74 ± 16.6 years; 29 females) were enrolled. Three patients (4.5%; 1 female) had been splenectomised and were excluded from further analyses. Fifty-five patients (87.3%) had IgM memory B cell depletion, and 18 (28.6%) died during hospitalisation (cumulative incidence rate 9.26/100 person-week; 5.8-14.7 95% CI). All patients who died had IgM memory B cell depletion. A superimposed infection was found in 6 patients (9.5%), all of them having IgM memory B cell depletion (cumulative incidence rate 3.08/100 person-week; 1.3-6.8 95% CI). At bivariable analyses, older age, sex, number of comorbidities, and peripheral blood lymphocyte count < 1500/µl were not correlated with IgM memory B cell depletion. A discrete-to-marked reduction of the B-cell compartment was also noticed in autoptic spleen specimens of two COVID-19 patients. We conclude that IgM memory B cells are commonly depleted in COVID-19 patients and this correlates with increased mortality and superimposed infections.