Signals of T h 2 immune response from COVID-19 patients requiring intensive care
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LETTER TO THE EDITOR
Signals of Th2 immune response from COVID-19 patients requiring intensive care Luca Roncati 1
&
Vincenzo Nasillo 1 & Beatrice Lusenti 1 & Giovanni Riva 1
Received: 18 April 2020 / Accepted: 27 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Dear Editor, Naїve T-helper cells (Th0) can respond to novel pathogens that the immune system has never encountered before, as is the specific case of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the positivesense single-stranded RNA virus responsible for the ongoing pandemic named coronavirus disease 2019 (COVID19). Depending on the infectious agent, Th0 polarize the immune response into T-helper type 1 (Th1), the default response in immunocompetent subjects to intracellular or phagocytosable pathogens (e.g. viruses, bacteria, protozoa, fungi) and mediated by macrophages and Tcytotoxic (Tc) cells (cell-mediated immunity), or into Thelper type 2 (Th2), classically directed against extracellular non-phagocytosable pathogens, for instance helminths, and whose main effectors are eosinophils, basophils and mastocytes, as well as B cells (humoral immunity) [1]. Eosinophils play a direct role in fighting RNA viruses, as demonstrated by the presence of RNases inside their granules [1]; however, they have been negatively associated with the pathophysiology of the respiratory virus infections, since they trigger bronchoconstriction and dyspnea, besides virus-induced exacerbations of allergic airways diseases, by releasing a large amount of cationic proteins and cytokines, among which interleukin-6 (IL6), a key mediator also for the development of the “cytokine storm” in COVID-19 fatal cases [2, 3]. At some extent, the smooth muscle cells in the tunica media of blood vessels can produce IL-6, too [4]. It belongs to Th2 cyto* Luca Roncati [email protected]; [email protected] 1
Hemolymphopathology Team, University Hospital Modena, Modena, Italy
kines class together with IL-4, IL-5, IL-9, IL-10, IL-13 and IL-25; contrariwise, IL-2, IL-12, interferon-γ and tumor necrosis factor-α are the main Th1 cytokines, able to stimulate the inducible form of the nitric oxide (NO) synthase to produce NO free radicals endowed with virucidal activity [1]. To minimize the contagion risk in healthcare personnel, we have prepared and examined a limited number of 15 peripheral blood smears from a wider series of hospitalized COVID-19 patients, just admitted to intensive care and monitored through blood tests; in all the cases, we have found cytological signals of T h2 immune response, represented by eosinophilia plus basophilia, degranulated eosinophils, Türk cells or plasma cells, together with rouleaux and Tc lymphopenia (Fig. 1). On the basis of our findings, for reasons still unclear, maybe related to the viral load, Th1 and Tc breakdown, antigenic cross-reactivity or the type of antigen-presenting cell stimulating Th0, the immune system mounts a Th2 response against SARS-CoV-2 in patients requiring intensive care, rather tha
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