Tissue-specific tolerance in fatal Covid-19

Successful host defence against a pathogen can involve resistance or tolerance, with implications for prioritising either antimicrobial or immunomodulatory therapeutic approaches. Hyper-inflammation occurs in Covid-19 and is associated with worse outcomes. The efficacy of dexamethasone in preventing mortality in critical Covid-19 suggests that inflammation has a causal role in death. Whether this deleterious inflammation is primarily a direct response to the presence of SARS-CoV-2 requiring enhanced resistance, or an independent immunopathologic process necessitating enhanced tolerance, is unknown. Here we report an aberrant immune response in fatal Covid-19, principally involving the lung and reticuloendothelial system, that is not clearly topologically associated with the virus, indicating tissue-specific tolerance of SARS-CoV-2. We found that inflammation and organ dysfunction in fatal Covid-19 did not map to the widespread tissue and cellular distribution of SARS-CoV-2 RNA and protein, both between and within tissues. A monocyte/myeloid-rich vasculitis was identified in the lung, along with an influx of macrophages/monocytes into the parenchyma. In addition, stereotyped abnormal reticulo-endothelial responses (reactive plasmacytosis and iron-laden macrophages) were present and dissociated from the presence of virus in lymphoid tissues. Our results support virus-independent immunopathology being one of the primary mechanisms underlying fatal Covid-19. This supports prioritising pathogen tolerance as a therapeutic strategy in Covid-19, by better understanding non-injurious organ-specific viral tolerance mechanisms and targeting aberrant macrophage and plasma cell responses.

Synchronous detection of multiple myeloma and acute myeloid leukemia: A diagnostic and therapeutic challenge

Introduction Synchronous detection of multiple myeloma and acute myeloid leukemia in a single patient is a rare coincidence. Treatment of these patients is still unclear, mostly based on acute myeloid leukemia strategies combined with bortezomib. Case report A 72-year-old male with no medical history was investigated for pancytopenia. On medical examination, he was complicated with a wide and severe skin infection on arm. On examination of bone marrow aspirate, 25% myeloblasts infiltration and additional 10% plasma cells were seen. Acute myeloid leukemia was diagnosed and plasma cell proliferation was attributed to reactive plasmacytosis due to skin infection. However, flowcytometric studies and immunohistochemical examination revealed two different cell populations with 30–40% atypical plasma cells and >20% myeloblasts. Serum M-protein detected by serum electrophoresis test and immunofixation test revealed a monoclonal IgG lambda band. He was diagnosed with concurrent acute myeloid leukemia and multiple myeloma without history of chemotherapy. Management and outcome: The patient was initially treated with bortezomib and dexamethasone for the myeloma. Subsequently, azacitidine was administered subcutaneously for the acute myeloid leukemia treatment. The tru-cut biopsy of the lesion on his arm revealed suppurative inflammatory findings and no malign cells detected. Antibiotherapy was started according to susceptibility. He expired after three months of survival. Discussion The synchronous occurrence of these two different clonal hematological malignancies is rare in hematology practice. Patient-based prospective studies and case series are needed to guide diagnosis and treatment strategies. Furthermore, this report highlights the importance of ruling out reactive plasmacytosis in patients with hematological malignancy who developed severe infections.

Pathomorphological and immunohistochemical features of lymph nodes in COVID-19 patients (autopsy study)

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

Role of CD138, CD56, and light chain immunohistochemistry in suspected and diagnosed plasma cell myeloma: A prospective study

Introduction: Plasma cells (PCs) have conventionally been counted on the bone marrow aspirate, and small focal involvement may be missed even on bone marrow biopsy sections. Material and Methods: We aimed to study the role of CD138, CD56, anti-κ, and anti-λ immunohistochemistry (IHC) to separate PC myeloma from reactive plasmacytosis and to study the utility of these in cases suspected as myelomas and lacking >10% PCs on bone marrow aspirate. The study comprised 35 diagnosed myelomas, 20 reactive plasmacytosis, and 19 M-band positive suspected myelomas. CD138 IHC was performed on all cases along with CD56, anti-κ, and anti-λ IHC. PCs were counted on CD138-immunostained sections by manual count and by image analysis. In addition, CD56 expression was correlated with clinical features in diagnosed myeloma group. Results: In all cases, both manual counts and image analysis, PC counts were significantly higher on the CD138 stained sections than bone marrow aspirates. It was seen that the manual PC counts and image analysis counts were equivalent in diagnosed myeloma cases. CD56 expression was seen in ~62.85% diagnosed myeloma cases while it was negative in cases of reactive plasmacytosis. CD56 expression was significantly higher in patients with lytic lesions (78.26% vs. 21.74%). CD138, anti-κ, and anti-λ IHC also helped classify 11/19 (57.8%) cases correctly. Conclusion: The use of CD138 along with the light chain and CD56 IHC adds a high diagnostic value in myeloma patients and suspected myeloma cases. The PCs can be counted manually on the CD138-immunostained sections and correlate well with the counts obtained by image analysis.

Morphologic confounders and CD19 negativity in a case of hairy cell leukemia.

Objectives:We report a case of hairy cell leukemia (HCL) initially misdiagnosed as plasma cell dyscrasia due to various clinical, morphological and immunophenotypic confounders.Methods and results:In a patient diagnosed of marrow plasmacytosis and serum monoclonal protein elsewhere and referred to our hospital, morphological evaluation of bone marrow aspirate smears and trephine biopsy, immunophenotyping, and molecular testing (BRAFV600E mutation) were done. Clinically, the patient was asymptomatic, bone marrow revealed plasmacytosis, mastocytosis and lymphocytosis with a few “hairy” cells. Immunophenotyping revealed features of HCL with aberrant CD10 expression and a subclone of CD19neg cells. A diagnosis of HCL with reactive plasmacytosis and mast cell hyperplasia was made and confirmed by immunophenotyping and molecular studies.Conclusion:Hematopathologists must be aware of various confounding factors and should judiciously use flow cytometric and molecular studies for attaining a proper diagnosis of HCL. We also report a very rare immunophenotypic aberrancy (CD 19 negativity) in HCL