Pathomorphological and immunohistochemical features of lymph nodes in COVID-19 patients (autopsy study)
Authors:   National Research Center for Hematology, Moscow, Russia, Kovrigina A.M. , Shalamova E.A. ,   National Research Center for Hematology, Moscow, Russia, Berezovskiy Yu.S. ,   Central Tuberculosis Research Institute, Moscow, Russia, Kalinin D.V. ,   A.V. Vishnevsky National Medical Research Center of Surgery, Moscow, Russia, Gretsov E.M. ,   Central Tuberculosis Research Institute, Moscow, Russia, Bagdasaryan T.R. ,   Central Tuberculosis Research Institute, Moscow, Russia, Semenova L.A. Semenova ,   Central Tuberculosis Research Institute, Moscow, Russia, Chebotarev D.I. ,   National Research Center for Hematology, Moscow, Russia, Samsonova M.V. ,   Research Institute of Pulmonology, Moscow, Russia,   A.S. Loginov Moscow Clinical Scientific Center of the Moscow Healthcare Department, Moscow, Russia, Chernyaev A.L. ,   Research Institute of Pulmonology, Moscow, Russia,   Research Institute of Human Morphology, Moscow, Russia,   Pirogov Russian National Research Medical University, Moscow, Russia, Mikhaleva L.M. ,   Research Institute of Human Morphology, Moscow, Russia,   City Clinical Hospital No. 31 of the Moscow Healthcare Department, Moscow, Russia, Mishnev O.D. ,   Pirogov Russian National Research Medical University, Moscow, Russia, Kurilina E.V. ,   National Medical Research Center of Cardiology, Moscow, Russia, Zayratyants O.V. ,   A.I. Evdokimov Moscow State University of Medicine and Dentistry of the Ministry of Healthcare of Russia, Moscow, Russia
Published: January 2021

Introduction. The pathogenesis of the novel coronavirus infection COVID-19 is being actively studied. Nevertheless, our up-to-date knowledge of lymphoid tissue response in the secondary immune organs dur-ing severe COVID-19 remains extremely limited. The aim of the study was to evaluate patterns of immu-nomorphological alterations in lymph nodes in patients with severe COVID-19 and to assess lymphocytes functional activity in them. Materials and methods. Lymph node tissue (autopsy material) from 17 deceased patients with severe COVID-19 was examined by histological and immunohistochemical methods using antibodies to CD4, CD8, CD20, CD30, CD123, CD138, PD-1. Results. Examined lymph nodes demonstrated lymphoid follicles reduction and paracortex expansion with reactive plasmacytosis and extrafollicular B-cell activation as well as sinus histiocytosis, variable hemophago-cytic cells, and blood vessel congestion. Red thrombi were observed in some lymph nodes. Hemorrhages in the stroma were frequent, and massive hemorrhages were found in individual nodes. Immunohistochemical study revealed CD4+ T-helpers predominance in the paracortex andcytotoxic CD8+ lymphocytes depletion together with an increase in the expression of both the PD-1 suppressor protein and the CD30 activation anti-gen on the lymphocyte surface. CD123-positive plasmacytoid dendritic cells resided in sinuses in abundance. Conclusion. Demonstrated B-associated zone reduction and cytotoxic T-lymphocytes depletion with an up-regulation of PD-1 expression in the lymph nodes in patients with severe COVID-19 indicate immune response exhaustion. At the same time, observed significant reactive plasmacytosis with the presence of numerous T-helper cells constitutes a morphological substrate of the humoral immunity. These findings might indicate the ineffec-tiveness of the humoral response at late stages of COVID-19 infection in context of cytotoxic immunity failure. Keywords: novel coronavirus infection, SARS-CoV-2, COVID-19, B- and T- immune response, lymph node