Monoclonal B-cell lymphocytosis (MBL) with normal lymphocyte counts is associated with decreased numbers of normal circulating B-cell subsets

Immune cell kinetics and antibody response in COVID-19 patients with low-count monoclonal B-cell lymphocytosis

Low-count monoclonal B-cell lymphocytosis (MBLlo ) 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 MBLlo versus non-MBL patients. For this study, we analyzed the kinetics of immune cells in blood of 336 COVID-19 patients (74 MBLlo 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, MBLlo 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, MBLlo 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 MBLlo patients. In summary, MBLlo 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.

Improved plasmablast response after repeated pneumococcal revaccinations following primary immunization with 13-valent pneumococcal conjugate vaccine or 23-valent pneumococcal polysaccharide vaccine in patients with chronic lymphocytic leukemia

BACKGROUND

Patients with chronic lymphocytic leukemia (CLL) show an immune dysfunction with increased risk of infections and poor response to vaccination. Streptococcus pneumoniae is a common cause of morbidity and mortality in CLL patients. In a previous randomized clinical trial, we found a superior immune response in CLL patients receiving conjugated pneumococcal vaccine compared to non-conjugated vaccine. The response to revaccination in CLL patients is scarcely studied. In this study, early humoral response to repeated revaccinations with pneumococcal vaccines was evaluated, by determination of B cell subsets and plasmablast dynamics in peripheral blood.

METHOD

CLL patients (n = 14) and immunocompetent controls (n = 31) were revaccinated with a 13-valent pneumococcal conjugate vaccine (PCV13) after previous primary immunization (3-6 years ago) with PCV13 or a 23-valent pneumococcal polysaccharide vaccine (PPSV23). Eight weeks after the first revaccination, all CLL patients received a second revaccination with PCV13 or PPSV23. B cell subsets including plasmablasts were analyzed in peripheral blood by flow cytometry, before and after the first and the second revaccination.

RESULTS

None of the CLL patients, but all controls, had detectable plasmablasts at baseline (p < 0.001). After the first revaccination with PCV13, the plasmablast proportions did not increase in CLL patients (p = 0.13), while increases were seen in controls (p < 0.001). However, after a second revaccination with PCV13 or PPSV23, plasmablasts increased compared to baseline also in CLL patients (p < 0.01). If no response was evident after first revaccination, only a second revaccination with PCV13 increased plasmablasts in contrast to PPSV23 revaccination. Patients with hypogammaglobulinemia and ongoing/previous CLL specific treatment responded poorly, also to a second revaccination.

CONCLUSION

In CLL patients, pneumococcal revaccination induced minor early plasmablast response compared to controls, but the response improved using a strategy of repeated doses with of conjugated T cell dependent pneumococcal vaccine.

Age- and Sex-Matched Normal Leukocyte Subset Ranges in the General Population Defined with the EuroFlow Lymphocyte Screening Tube (LST) for Monoclonal B-Cell Lymphocytosis (MBL) vs. Non-MBL Subjects

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 (MBLlo), 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 MBLlo 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 MBLlo—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 MBLlo subjects, few differences in the absolute cell counts by age (vs. non-MBL) were observed, and MBLlo 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 MBLlo 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 MBLlo subjects.

Mass cytometry analysis reveals attrition of naïve and anergized self-reactive non-malignant B cells in chronic lymphocytic leukemia patients

Chronic Lymphocytic Leukemia (CLL) is characterized by the progressive accumulation of monoclonal mature B lymphocytes. Autoimmune complications are common in CLL occurring in up to a quarter of all patients during the course of the illness. Etiology of autoimmunity in CLL is unknown but it is widely admitted that the pathogenic auto-Abs do not originate from the tumoral clone but from the non-malignant B cell pool. This indicates that the developmental scheme of non-malignant B cells could also be perturbed in CLL patients. To address this question, we have designed a B cell-centered antibody panel and used time-of-flight mass cytometry to compare the residual non-malignant B cell pool of CLL patients with the peripheral B cell pool of age-matched healthy donors. We show that the non-malignant B cell compartment of the patients is characterized by profound attrition of naïve B cells and of a population of anergized autoreactive B cells, suggesting impaired B cell lymphopoeisis as well as perturbations of the B cell tolerance checkpoints.

The humoral immune response to high-dose influenza vaccine in persons with monoclonal B-cell lymphocytosis (MBL) and chronic lymphocytic leukemia (CLL)

BACKGROUND

Limited data are available regarding the immunogenicity of high-dose influenza vaccine among persons with chronic lymphocytic leukemia (CLL) and monoclonal B cell lymphocytosis (MBL).

METHODS

A prospective pilot study of humoral immune responses to 2013-2014 and 2014-2015 high-dose trivalent influenza vaccine (HD IIV; Fluzone® High-Dose; Sanofi Pasteur) was conducted among individuals with MBL and previously untreated CLL. Serum hemagglutination inhibition (HAI) antibody titers were measured at baseline and Day 28 after vaccination; seroprotection and seroconversion rates were determined. Memory B cell responses were assessed by B-cell enzyme-linked immune absorbent spotassays.

RESULTS

Thirty subjects (17 CLL and 13 MBL) were included. Median age was 69.5 years. Day 28 seroprotection rates for the cohort were 19/30 (63.3%) for A/H1N1; 21/23 (91.3%) for A/H3N2; and 13/30 (43.3%) for influenza B. Those with MBL achieved higher day 28 HAI geometric mean titers (54.1 [4.9, 600.1] vs. 12.1 [1.3, 110.1]; p = 0.01) and higher Day 28 seroprotection rates (76.9% vs. 17.6%; p = 0.002) against the influenza B-vaccine strain virus than those with CLL.

CONCLUSIONS

Immunogenicity of the HD IIV3 in patients with CLL and MBL is lower than reported in healthy adults. Immunogenicity to influenza B was greater in those with MBL than CLL.

Immunophenotypic analysis reveals heterogeneity and common biologic aspects in monoclonal B-cell lymphocytosis

Monoclonal B-cell lymphocytosis (MBL) is the presence of small B-cell clones in the peripheral blood of healthy subjects. Most MBL have the characteristic phenotype of chronic lymphocyte leukemia (chronic lymphocytic leukemia (CLL)-like MBL), and depending on the number of monoclonal B-cells, may characterize a preclinical stage of the CLL. However, there are also MBL with an atypical (CD5(+) CD20(+/bright) CD23(dim/-) ) or a CD5(neg) phenotype, which remain largely unexplored. We performed an extended immunophenotypic, cytogenetic, and hematologic analysis in 75 CLL-like, 39 atypical, 50 CD5(neg) , and 7 biphenotypic MBL cases to detect differences or similarities among the MBL subsets. The phenotypic analysis showed expression variations in many surface markers and a wide spectrum of disease-specific phenotypes within each MBL subtype. Interphase fluorescent in situ hybridization analysis showed a different panel of aberrations according to the phenotype. Overall, del(13q14) and +12 were the most common abnormalities (39%), whereas del(11q13), del(17p13), and del(6q23) were detected only in 3, 1, and 0 cases, respectively. A comparison of MBL with overt chronic lymphoproliferations revealed common aspects in the preclinical state, regarding both the kind of cytogenetic aberrations detected and the lymphocyte composition. Our findings highlight not only the heterogeneity among MBL subsets but also indicate common biologic features which differentiate MBL from clinical disease.

New insights into monoclonal B-cell lymphocytosis

Monoclonal B-cell lymphocytosis (MBL) is a premalignant condition characterized by the presence of less than 5000/μL circulating clonal B cells in otherwise healthy individuals. Three subcategories have been identified according to the immunophenotypic features: CLL-like, CD5(+) atypical, and CD5(−) MBL. CLL-like MBL is by far the most frequent and best studied category and further divided in low-count [LC] and high-count [HC] MBL, based on a cutoff value of 500/μL clonal B cells. LC-MBL typically remains stable and probably does not represent a truly premalignant condition, but rather an age-related immune senescence. On the other hand, HC-MBL is closely related to CLL-Rai0, bearing similar immunogenetic profile, and is associated with an annual risk of progression to CLL requiring therapy at a rate of 1.1%. Currently there are no reproducible factors for evaluating the risk of progression to CLL. CD5(−) MBL is characterized by an immunophenotype consistent with marginal zone origin and displays many similarities with marginal zone lymphomas (MZL), mainly the splenic MZL. The cutoff value of 5000/μL clonal B cells cannot probably be applied in CD5(−) MBL, requiring a new definition to describe those cases.

MBL versus CLL: how important is the distinction?

Monoclonal B-cell lymphocytosis (MBL) is defined as a clonal B-cell expansion whereby the B-cell count is less than 5 × 10(9)/L and no symptoms or signs of lymphoproliferative disorders are detected. Based on B-cell count, MBL is further divided into low-count and clinical MBL. While low-count MBL seems to carry relevance mostly from an immunological perspective, clinical MBL and chronic lymphocytic leukemia appear to be overlapping entities. Only a deeper knowledge of molecular pathways and microenvironmental influences involved in disease evolution will help to solve the main clinical issue, i.e. how to differentiate nonprogressive and progressive cases requiring intensive follow-up.

Monoclonal B cell lymphocytosis--what does it really mean?

Monoclonal B cell Lymphocytosis (MBL) or similar terms have been used for decades to describe the presence of light-chain restricted B lymphocytes with uncertain clinical significance, usually having a phenotype consistent with chronic lymphocytic leukemia (CLL). As diagnostic technology improved, ever smaller monoclonal B cell populations were identifiable in the population, and approximately half of people over 90 years old have a minimal (<1 cell/μL) circulating CLL-like B cell population. These minimal CLL-like B cell populations share some molecular characteristics with CLL, but have no clinical significance. In contrast, CLL-like MBL cases detected through hospital investigations are biologically indistinguishable from early stage CLL, but the neoplastic B cell levels are usually stable over time and the risk of progressive disease requiring treatment is much lower than for early stage CLL. However, there is usually partial or complete depletion of normal B cells, with an increased relative risk of severe infection, comparable to early stage CLL, which may impair overall survival.

Immunogenetics shows that not all MBL are equal: the larger the clone, the more similar to CLL

Low-count and high-count monoclonal B-cell lymphocytosis (MBL) have distinct immunogenetic signatures, with only the latter resembling CLL. Rather than a true premalignant condition, low-count MBL may merely reflect immune senescence or result from persistent antigen stimulation.

Common infectious agents and monoclonal B-cell lymphocytosis: a cross-sectional epidemiological study among healthy adults

Background

Risk factors associated with monoclonal B-cell lymphocytosis (MBL), a potential precursor of chronic lymphocytic leukaemia (CLL), remain unknown.

Methods

Using a cross-sectional study design, we investigated demographic, medical and behavioural risk factors associated with MBL. “Low-count” MBL (cases) were defined as individuals with very low median absolute count of clonal B-cells, identified from screening of healthy individuals and the remainder classified as controls. 452 individuals completed a questionnaire with their general practitioner, both blind to the MBL status of the subject. Odds ratios (OR) and 95% confidence interval (CI) for MBL were estimated by means of unconditional logistic regression adjusted for confounding factors.

Results

MBL were detected in 72/452 subjects (16%). Increasing age was strongly associated with MBL (P-trend<0.001). MBL was significantly less common among individuals vaccinated against pneumococcal or influenza (OR 0.49, 95% confidence interval (CI): 0.25 to 0.95; P-value = 0.03 and OR: 0.52, 95% CI: 0.29 to 0.93, P-value = 0.03, respectively). Albeit based on small numbers, cases were more likely to report infectious diseases among their children, respiratory disease among their siblings and personal history of pneumonia and meningitis. No other distinguishing epidemiological features were identified except for family history of cancer and an inverse relationship with diabetes treatment. All associations described above were retained after restricting the analysis to CLL-like MBL.

Conclusion

Overall, these findings suggest that exposure to infectious agents leading to serious clinical manifestations in the patient or its surroundings may trigger immune events leading to MBL. This exploratory study provides initial insights and directions for future research related to MBL, a potential precursor of chronic lymphocytic leukaemia. Further work is warranted to confirm these findings.