Reference ranges of blood-circulating leukocyte populations by, e.g., age and sex, are required for monitoring immune-cell kinetics. Most previous reports in which flow cytometry has been used to define the reference ranges for leukocyte counts included a limited number of donors and/or cell populations and/or did not consider age and sex simultaneously. Moreover, other factors not previously considered in the definition of normal ranges, such as the presence of chronic-lymphocytic-leukemia (CLL)-like low-count monoclonal B-cell lymphocytosis (MBL^lo), might also be associated with an altered distribution of leukocytes in blood in association with an immunodeficiency and increased risk of infection and cancer. Here, we established reference cell-count ranges for the major populations of leukocytes in blood of non-MBL and MBL^lo adult Caucasians matched by age and sex using the EuroFlow Lymphocyte Screening Tube (LST). A total of 706 Caucasian adult donors—622 non-MBL and 84 MBL^lo—were recruited from the general population. Among non-MBL donors, the total leukocyte, neutrophil, basophil dendritic cell and monocyte counts remained stable through adulthood, while the absolute numbers of T- and B-cell populations and plasma cells decreased with age. The number of eosinophils and NK-cell increased over time, with clear differences according to sex for certain age ranges. In MBL^lo subjects, few differences in the absolute cell counts by age (vs. non-MBL) were observed, and MBL^lo men and women showed similar trends to non-MBL subjects except for the B-cell count drop observed in >70 y-men, which was more pronounced in MBL^lo vs. non-MBL controls. Building robust age- and sex-matched reference ranges for the most relevant immune-cell populations in the blood of non-MBL donors is essential to appropriately identify an altered immune status in different clinical settings and highlight the altered immune-cell profiles of MBL^lo subjects.

Introducción y objetivos: Las secuelas cardiacas tras la infección por SARS-CoV-2 todavía están poco documentadas. Se realizó un estudio transversal en trabajadores sanitarios para estudiar la prevalencia de afección pericárdica y miocárdica tras la infección por SARS-CoV-2. Métodos: Se estudió a 139 trabajadores sanitarios con infección previa por SARS-CoV-2 confirmada. Los participantes se sometieron a evaluación clínica, electrocardiograma, pruebas de laboratorio que incluyeron el perfil de células inmunitarias y resonancia magnética cardiaca (RMC). El diagnóstico clínico de pericarditis se realizó según los criterios clásicos y el diagnóstico clínico de miocarditis, ante la presencia de al menos 2 criterios en la RMC. Resultados: La mediana de edad fue 52 (intervalo, 41-57) años, el 71,9% eran mujeres y el 16,5% se había hospitalizado previamente por neumonía por COVID-19. En la evaluación (10,4 [9,3-11,0] semanas después de los síntomas de infección), todos los participantes presentaban estabilidad hemodinámica. El 41,7% tenía dolor torácico, disnea o palpitaciones; el 49,6%, alteraciones electrocardiográficas; el 7,9%, elevación de NT-proBNP; el 0,7%, elevación de troponina y el 60,4%, alteraciones en la RMC. El 30,9% de los participantes cumplían los criterios clínicos establecidos de pericarditis o miocarditis: pericarditis aislada en el 5,8%, miopericarditis en el 7,9% y miocarditis aislada en el 17,3%. La mayoría de los participantes (73,2%) mostraron recuentos alterados de células inmunitarias en sangre, en particular diminución de eosinófilos (27,3%; p < 0,001) y aumento del número de células T citotóxicas (17,3%; p < 0,001). La sospecha clínica de pericarditis se asoció (p < 0,005) particularmente con un elevado número de células T citotóxicas y recuento de eosinófilos disminuido, mientras que los participantes con sospecha clínica de miopericarditis o miocarditis tenían recuentos de neutrófilos, células natural killer y células plasmáticas más bajos (p < 0,05). Conclusiones: La afección pericárdica y miocárdica con estabilidad hemodinámica es frecuente después de la infección por SARS-CoV-2 y se asocia con perfiles de células inmunitarias específicas. Introduction and objectives The cardiac sequelae of SARS-CoV-2 infection are still poorly documented. We conducted a cross-sectional study in healthcare workers to report evidence of pericardial and myocardial involvement after SARS-CoV-2 infection. Methods We studied 139 healthcare workers with confirmed past SARS-CoV-2 infection. Participants underwent clinical assessment, electrocardiography, and laboratory tests, including immune cell profiling and cardiac magnetic resonance (CMR). Clinically suspected pericarditis was diagnosed when classic criteria were present and clinically suspected myocarditis was based on the combination of at least 2 CMR criteria. Results Median age was 52 (41-57) years, 71.9% were women, and 16.5% were previously hospitalized for COVID-19 pneumonia. On examination (10.4 [9.3-11.0] weeks after infection-like symptoms), participants showed hemodynamic stability. Chest pain, dyspnea or palpitations were present in 41.7% participants, electrocardiographic abnormalities in 49.6%, NT-proBNP elevation in 7.9%, troponin in 0.7%, and CMR abnormalities in 60.4%. A total of 30.9% participants met criteria for either pericarditis and/or myocarditis: isolated pericarditis was diagnosed in 5.8%, myopericarditis in 7.9%, and isolated myocarditis in 17.3%. Most participants (73.2%) showed altered immune cell counts in blood, particularly decreased eosinophil (27.3%; P < .001) and increased cytotoxic T cell numbers (17.3%; P < .001). Clinically suspected pericarditis was associated (P < .005) with particularly elevated cytotoxic T cells and decreased eosinophil counts, while participants diagnosed with clinically suspected myopericarditis or myocarditis had lower (P < .05) neutrophil counts, natural killer-cells, and plasma cells. Conclusions Pericardial and myocardial involvement with clinical stability are frequent after SARS-CoV-2 infection and are associated with specific immune cell profiles.

Low‐count monoclonal B‐cell lymphocytosis (MBL^lo) has been associated with an underlying immunodeficiency and has recently emerged as a new risk factor for severe COVID‐19. Here, we investigated the kinetics of immune cell and antibody responses in blood during COVID‐19 of MBL^lo versus non‐MBL patients. For this study, we analyzed the kinetics of immune cells in blood of 336 COVID‐19 patients (74 MBL^lo and 262 non‐MBL), who had not been vaccinated against SARS‐CoV‐2, over a period of 43 weeks since the onset of infection, using high‐sensitivity flow cytometry. Plasma levels of anti‐SARS‐CoV‐2 antibodies were measured in parallel by ELISA. Overall, early after the onset of symptoms, MBL^lo COVID‐19 patients showed increased neutrophil, monocyte, and particularly, plasma cell (PC) counts, whereas eosinophil, dendritic cell, basophil, and lymphocyte counts were markedly decreased in blood of a variable percentage of samples, and with a tendency toward normal levels from week +5 of infection onward. Compared with non‐MBL patients, MBL^lo COVID‐19 patients presented higher neutrophil counts, together with decreased pre‐GC B‐cell, dendritic cell, and innate‐like T‐cell counts. Higher PC levels, together with a delayed PC peak and greater plasma levels of anti‐SARS‐CoV‐2‐specific antibodies (at week +2 to week +4) were also observed in MBL^lo patients. In summary, MBL^lo COVID‐19 patients share immune profiles previously described for patients with severe SARS‐CoV‐2 infection, associated with a delayed but more pronounced PC and antibody humoral response once compared with non‐MBL patients.

Background/Objectives: Despite the current international prognostic index for chronic lymphocytic leukemia (CLL) being widely accepted and broadly used, it does not consider the kinetics of the B-cell clone over time. Here, we investigated the potential association between distinct features of leukemic cells and other immune cells in blood and the kinetics of clonal B-cells in CLL stage Binet A/Rai 0 (A/0) patients; Methods: Based on the leukemia cell kinetics, 69 CLL A/0 cases followed for a median of 105 months were classified as carrying stable (n = 53) vs. rapidly increasing in size (n = 16) CLL clones; Results: Patients with increasing CLL clones had a significantly higher risk of disease progression and shortened time to first therapy vs. those carrying stable B-cell clones (p ≤ 0.001). Strikingly, the distribution of various immune-cell populations in blood at diagnosis also differed significantly between the two groups, with lower Tαβ CD4⁺CD8^lo cell counts (p = 0.03), a greater switched/unswitched memory B-cell ratio (p = 0.01), and higher plasma cell counts (p = 0.05) in CLL with increasing vs. stable clones. Multivariate analysis revealed that the number of circulating clonal B-cells (≥15 × 10⁹/L) and Tαβ CD4⁺CD8^lo cells (≤35 cells/µL), together with an IGHV unmutated gene status at diagnosis, were independent predictors of an increasing CLL clone; Conclusions: Altogether, these data suggest that the expansion of the CLL clone in stage A/0 patients may depend on both the intrinsic characteristics of CLL cells and the surrounding immune microenvironment.

The early immune kinetics after SARS-CoV-2 vaccination remain poorly understood, particularly among individuals with low-count monoclonal B-cell lymphocytosis (MBLlo). We investigated the cellular and humoral kinetics in the blood of 50 non-MBL healthy donors (HD) vs. 16 MBLlo subjects after SARS-CoV-2 vaccination, who were subclassified according to their history of previous exposure to SARS-CoV-2 into SARS-CoV-2 naïve and previously infected subjects. Overall, we found decreased neutrophil and lymphocyte counts at day +4 following each dose in non-MBL HD, together with an earlier and higher increase in plasma cell (PC) counts and SARS-CoV-2-specific antibody levels after the first vaccine in previously infected non-MBL HD. MBLlo subjects showed a similar profile, except for lower B-cell and higher PC counts after vaccination, and a trend towards a higher (but delayed) antibody response. In summary, we found different cell-kinetic profiles following vaccination in SARS-CoV-2 naïve vs. previously infected non-MBL HD (earlier PC and antibody responses in the latter group); additionally, MBLlo subjects had significantly lower B-cell and higher PC counts after vaccination, and a delayed SARS-CoV-2-specific antibody response.