Quantitative and qualitative alterations of circulating myeloid cells and plasmacytoid DC in SARS-CoV-2 infection.

SARS-CoV-2 is responsible for a new infectious disease (COVID-19) in which individuals can either remain asymptomatic or progress from mild to severe clinical conditions including acute respiratory distress syndrome and multiple organ failure. The immune mechanisms that potentially orchestrate the pathology in SARS-CoV-2 infection are complex and only partially understood. There is still paucity of data on the features of myeloid cells involved in this viral infection. For this reason, we investigated the different activation status profiles and the subset distribution of myeloid cells and their correlation with disease progression in 40 COVID-19 patients at different stages of disease. COVID-19 patients showed a decrease in the absolute number of plasmacytoid and myeloid dendritic cells, different subset distribution of monocytes and different activation patterns of both monocytes and neutrophils, coupled to a significant reduction of HLA-DR monocyte levels. We found that some of these alterations are typical of all COVID-19 patients, while some others vary at different stages of the disease and correlate with biochemical parameters of inflammation. Collectively, these data suggest that not only the lymphoid, but also the myeloid compartment, is severely affected by SARS-CoV-2 infection.

Rapid evaluation of T cell clonality in the diagnostic work-up of mature T cell neoplasms: TRBC1-based flow cytometric assay experience.

The identification of mature T cell neoplasms by flow cytometry is often challenging, due to overlapping features with reactive T cells and limitations of currently available T cell clonality assays. The description of an antibody specific for one of two mutually exclusive T cell receptor (TCR) ß-chain constant regions (TRBC1) provides an opportunity to facilitate the detection of clonal TCRαß+ T cells based on TRBC-restriction. Here we prospectively analyzed 14 healthy controls and 63 patients with the flow cytometry protocol currently used for suspected T cell neoplasm implemented with immunostaining targeting TRBC1. Specimens were firstly classified in 3 groups based on clinical records data, laboratory findings and immunophenotypic features. T cell clonality was assessed by TCR Vß repertoire analysis and the new rapid TRBC1 assay. Results showed that TRBC1 unimodal expression was unequivocally associated with samples presenting with immunophenotypic aberrancies. Moreover, we demonstrated that the use of TRBC1 is useful in solving uncertain cases and confirmed the high sensitivity of the method in identifying small T cell clones of uncertain significance (T-CUS). Finally, we found a high degree of concordance (97%) comparing the currently available clonality assessment methods with the proposed new method. In conclusion, our results provided real-life evidence of the utility of TRBC1 introduction in the flow cytometric clonality evaluation for the routine diagnostic work-up of T cell neoplasms.