Age-associated distribution of normal B-cell and plasma cell subsets in peripheral blood

Background: Humoral immunocompetence develops stepwise throughout life and contributes to individual susceptibility to infection, immunodeficiency, autoimmunity, and neoplasia. Immunoglobulin heavy chain (IgH) isotype serum levels can partly explain such age-related differences, but their relationship with the IgH isotype distribution within memory B-cell (MBC) and plasma cell (PCs) compartments remains to be investigated. Objective: We studied the age-related distribution of MBCs and PCs expressing different IgH isotypes in addition to the immature/transitional and naive B-cell compartments. Methods: B-cell and PC subsets and plasma IgH isotype levels were studied in cord blood (n = 19) and peripheral blood (n = 215) from healthy donors aged 0 to 90 years by using flow cytometry and nephelometry, respectively. Results: IgH-switched MBCs expressing IgG1, IgG2, IgG3, IgA1, and IgA2 were already detected in cord blood and newborns at very low counts, whereas CD27+IgM++IgD+ MBCs only became detectable at 1 to 5 months and remained stable until 2 to 4 years, and IgD MBCs peaked at 2 to 4 years, with both populations decreasing thereafter. MBCs expressing IgH isotypes of the second immunoglobulin heavy chain constant region (IGHC) gene block (IgG1, IgG3, and IgA1) peaked later during childhood (2-4 years), whereas MBCs expressing third IGHC gene block immunoglobulin isotypes (IgG2, IgG4, and IgA2) reached maximum values during adulthood. PCs were already detected in newborns, increasing in number until 6 to 11 months for IgM, IgG1, IgG2, IgG3, IgA1, and IgA2; until 2 to 4 years for IgD; and until 5 to 9 years for IgG4 and decreasing thereafter. For most IgH isotypes (except IgD and IgG4), maximum plasma levels were reached after PC and MBC counts peaked. Conclusions: PC counts reach maximum values early in life, followed by MBC counts and plasma IgH isotypes. Importantly, IgH isotypes from different IGHC gene blocks show different patterns, probably reflecting consecutive cycles of IgH isotype switch recombination through life

Defects in memory B-cell and plasma cell subsets expressing different immunoglobulin-subclasses in patients with CVID and immunoglobulin subclass deficiencies

Background: Predominantly antibody deficiencies (PADs) are the most prevalent primary immunodeficiencies, but their B-cell defects and underlying genetic alterations remain largely unknown. Objective: We investigated patients with PADs for the distribution of 41 blood B-cell and plasma cell (PC) subsets, including subsets defined by expression of distinct immunoglobulin heavy chain subclasses. Methods: Blood samples from 139 patients with PADs, 61 patients with common variable immunodeficiency (CVID), 68 patients with selective IgA deficiency (IgAdef), 10 patients with IgG subclass deficiency with IgA deficiency, and 223 age matched control subjects were studied by using flow cytometry with EuroFlow immunoglobulin isotype staining. Patients were classified according to their B-cell and PC immune profile, and the obtained patient clusters were correlated with clinical manifestations of PADs. Results: Decreased counts of blood PCs, memory B cells (MB Cs), or both expressing distinct IgA and IgG subclasses were identified in all patients with PADs. In patients with IgAdef, B-cell defects were mainly restricted to surface membrane (sm)IgA(+) PCs and MBCs, with 2 clear subgroups showing strongly decreased numbers of smIgA(+) PCs with mild versus severe smIgA(+) MBC defects and higher frequencies of nonrespiratory tract infections, autoimmunity, and affected family members. Patients with IgG subclass deficiency with IgA deficiency and those with CVID showed defects in both smIgA(+) and smIgG(+) MBCs and PCs. Reduced numbers of switched PCs were systematically found in patients with CVID (absent in 98%), with 6 different defective MBC (and clinical) profiles: (1) profound decrease in MBC numbers; (2) defective CD27(+) MBCs with almost normal IgG(3)(+) MBCs; (3) absence of switched MBCs; and (4) presence of both unswitched and switched MBCs without and; (5) with IgG(2)(+) MBCs; and (6) with IgA(1)(+) MBCs. Conclusion: Distinct PAD defective B-cell patterns were identified that are associated with unique clinical profiles

High frequency of low-count monoclonal B-cell lymphocytosis in hospitalized COVID-19 patients

Low-count monoclonal B-cell lymphocytosis (MBLlo, <500 clonal B-cells/μL) is a highly prevalent condition in the general population (4% to 16% of otherwise healthy adults), which increases significantly with age.1-7 In most cases, clonal B-cells share phenotypic and cytogenetic features with chronic lymphocytic leukemia (CLL), but only a small fraction (≈1.8%) progresses to high-count MBL (MBLhi; ≥500 and <5000 clonal B-cells/μL)3 in the medium-term.8 However, previous reports showed that MBLlo subjects had an increased risk of severe infections in association with a (predominantly) secondary antibody deficiency,8-10 suggesting that MBLlo might be a risk marker for developing more severe infections.This work was supported by the Instituto de Salud Carlos III (Ministerio de Ciencia e Innovación, Madrid, Spain, and FONDOS FEDER (a way to build Europe) grants CB16/12/00400 (CIBERONC), COV20/00386, and PI17/00399; the Consejería de Educación and the Gerencia Regional de Salud, Consejería de Sanidad from Junta de Castilla y León (Valladolid, Spain) grants SA109P20 and GRS-COVID-33/A/20; the European Regional Development Fund (INTERREG POCTEP Spain-Portugal) grant 0639-IDIAL-NET-3-3; and the CRUK (United Kingdom), Fundación AECC (Spain), and Associazione Italiana per la Ricerca Sul Cancro (Italy) “Early Cancer Research Initiative Network on MBL (ECRINM3)” ACCELERATOR award. G.O.-A. is supported by a grant from the Consejería de Educación, Junta de Castilla y León (Valladolid, Spain); B.F.-H. was supported by grant 0639-IDIAL-NET-3-3.Peer reviewe

Gestión del proceso posanalítico en los laboratorios clínicos según los requisitos de la norma ISO 15189:2012. Consideraciones sobre la revisión, notificación y comunicación de los resultados

El objeto de este trabajo es establecer unas consideraciones para facilitar la gestión del proceso posanalítico respecto a la revisión, notificación y comunicación de los resultados, de acuerdo con los requisitos de la Norma UNE-EN ISO 15189:2013. El ámbito de aplicación incluye las actividades del proceso posanalítico del laboratorio clínico, así como el personal implicado en él (dirección y personal del laboratorio). Se indican los criterios y la información necesaria para realizar la revisión y validación de los resultados de las pruebas analíticas y así enviar a los destinatarios informes claros, asegurando siempre una transcripción fidedigna de los resultados e incluyendo toda la información necesaria para su correcta interpretación. Asimismo, se describen los requisitos para una correcta comunicación de los resultados del laboratorio, haciendo especial hincapié en la comunicación de aquellos resultados alarmantes o críticos. En algunos países de Europa es obligatoria la acreditación, total o parcial, de los laboratorios clínicos, siguiendo la Norma ISO 15189 y esta parece ser la hoja de ruta marcada en otros muchos países. Por ello, es indispensable la comprensión de sus requisitos para realizar una implementación progresiva y más fácil