Monocyte Production of C1q Potentiates CD8+ T Cell Function Following Respiratory Viral Infection.

Respiratory viral infections remain a leading cause of morbidity and mortality. Using a murine model of human metapneumovirus (HMPV), we identified recruitment of a C1q-expressing inflammatory monocyte population concomitant with viral clearance by adaptive immune cells. Genetic ablation of C1q led to reduced CD8+ T cell function. Production of C1q by a myeloid lineage was necessary to enhance CD8+ T cell function. Activated and dividing CD8+ T cells expressed a C1q receptor, gC1qR. Perturbation of gC1qR signaling led to altered CD8+ T cell IFN-γ production, metabolic capacity, and cell proliferation. Autopsy specimens from fatal respiratory viral infections in children demonstrated diffuse production of C1q by an interstitial population. Humans with severe COVID-19 infection also demonstrated upregulation of gC1qR on activated and rapidly dividing CD8+ T cells. Collectively, these studies implicate C1q production from monocytes as a critical regulator of CD8+ T cell function following respiratory viral infection. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Schwannian and Perineuriomatous Differentiation in a Series of Giant Congenital Melanocytic Nevi.

ABSTRACT: Close relationship between melanocytes and neural cells is accepted to reflect their common derivation from the neural crest and tumors combining both elements. We present a series of 10 patients with giant congenital melanocytic nevi (CMN) in which a secondary proliferation (11 lesions) with schwannian and/or perineuriomatous differentiation developed in the course of the disease. The age of the patients (4 male and 6 female) at the time of surgery and histological assessment varied from 3 months to 57 years. Histopathologically, the following subgroups were delineated: (1) nodular/tumoriform "neurotization" in CMN, (2) diffuse neurofibroma-like proliferation within CMN, (3) plexiform neurofibroma-like proliferation within CMN, and (4) diffuse perineuriomatous (hybrid schwannomatous-perineuriomatous) differentiation in CMN. We review the pertinent literature, including the role of recently identified Schwann cell precursors which are believed to represent the nerve-associated state of neural crest-like cells that persists into later developmental stages.

The Spectrum of Sarcina Colonization in the Gastrointestinal Tract of Pediatric and Adolescent Patients.

Introduction. Sarcina organisms are rare, gram-positive, sugar-fermenting cocci, identifiable in tissues only by histologic examination or molecular testing. Since its discovery, the pathogenicity and relevance of Sarcina in the human gastrointestinal tract has remained ill-defined. A recent literature review of 66 reported examples demonstrated the potential for severe complications such as emphysematous gastritis and gastric perforation. In pediatrics, colonization is associated with mucosal alterations and/or gastrointestinal dysmotility/obstruction with variable outcomes, including death secondary to gastric perforation. Yet, the features of Sarcina colonization within the gastrointestinal tract of adolescents are poorly understood and rarely reported. Methods. We present the gastrointestinal histopathological findings and the complete history of 4 pediatric patients with Sarcina colonization at our institution. Additionally a literature review with focus in the keywords "Sarcina" and "gastrointestinal' was performed, and the clinical and histopathological features of all previously reported examples of Sarcina in the gastrointestinal tract of pediatric patients were summarized. Results. All 4 patients had delayed gastric emptying, 3 of them due to neurologic disease, and one with pyloric obstruction due to duodenal ulceration with Helicobacter gastritis. In the 3 patients with available esophageal biopsies, it was associated to esophagitis with increased intraepithelial eosinophils. Conclusion. The potential pathogenicity of Sarcina colonization in the gastrointestinal tract of pediatric patients needs to be reevaluated. Due to potential serious complications, the identification of these organisms in the gastrointestinal tract sample should be reported and warrants further evaluation for possible gastrointestinal dysmotility or other mucosal alterations.