Relationships between B cell cytokine production in secondary lymphoid follicles and apoptosis of germinal center B lymphocytes

High-Dose Intravenous Immunoglobulins in the Treatment of Severe Acute Viral Pneumonia: The Known Mechanisms and Clinical Effects

The current outbreak of viral pneumonia, caused by novel coronavirus SARS-CoV-2, is the focus of worldwide attention. The WHO declared the COVID-19 outbreak a pandemic event on Mar 12, 2020, and the number of confirmed cases is still on the rise worldwide. While most infected individuals only experience mild symptoms or may even be asymptomatic, some patients rapidly progress to severe acute respiratory failure with substantial mortality, making it imperative to develop an efficient treatment for severe SARS-CoV-2 pneumonia alongside supportive care. So far, the optimal treatment strategy for severe COVID-19 remains unknown. Intravenous immunoglobulin (IVIg) is a blood product pooled from healthy donors with high concentrations of immunoglobulin G (IgG) and has been used in patients with autoimmune and inflammatory diseases for more than 30 years. In this review, we aim to highlight the known mechanisms of immunomodulatory effects of high-dose IVIg therapy, the immunopathological hypothesis of viral pneumonia, and the clinical evidence of IVIg therapy in viral pneumonia. We then make cautious therapeutic inferences about high-dose IVIg therapy in treating severe COVID-19. These inferences may provide relevant and useful insights in order to aid treatment for COVID-19.

Ocrelizumab, a humanized anti-CD20 monoclonal antibody, in the treatment of patients with rheumatoid arthritis: a phase I/II randomized, blinded, placebo-controlled, dose-ranging study

OBJECTIVE

Ocrelizumab, a humanized anti-CD20 monoclonal antibody, was studied in a first-in-human trial in rheumatoid arthritis (RA) patients receiving concomitant methotrexate (MTX).

METHODS

The ACTION trial was a combined phase I/II study of placebo plus MTX versus ocrelizumab plus MTX in 237 RA patients (intent-to-treat population). During phase I, 45 patients were treated with 1 of 5 escalating doses of study drug (infusions on days 1 and 15, 10-1,000 mg per each infusion). An additional 192 patients were randomized during phase II. Eligible patients had active disease, an inadequate response to treatment with at least MTX, rheumatoid factor positivity, and elevated levels of acute-phase reactants. The total study duration was 72 weeks. B cell pharmacodynamics over time was investigated.

RESULTS

Baseline demographics were similar among the treatment groups. Based on the entire 72-week data set, the incidence of serious adverse events in the ocrelizumab-treated patients was 17.9%, as compared with 14.6% in placebo-treated patients. The incidence of serious infections was 2.0% in all ocrelizumab-treated patients and 4.9% in placebo-treated patients. Infusion-associated adverse events were mostly grade 1 or grade 2 and were more frequent around the time of the first infusion. No serious infusion-associated adverse events were reported in the ocrelizumab group. Evidence of clinical activity was observed at all doses evaluated. Peripheral B cell depletion after infusion was rapid at all doses, with earlier repletion of B cells at doses of 10 mg and 50 mg. Human anti-human antibodies were detected in 19% and 10%, respectively, of those receiving 10 mg and 50 mg of ocrelizumab, compared with 0-5% of those receiving 200, 500, and 1,000 mg.

CONCLUSION

Ocrelizumab therapy in combination with MTX was well tolerated. Doses of 200 mg (2 infusions) and higher showed better clinical responses, better reduction of C-reactive protein levels, and very low immunogenicity.

Improvement in patient-reported outcomes in a rituximab trial in patients with severe rheumatoid arthritis refractory to anti-tumor necrosis factor therapy

OBJECTIVE

To assess the effects of treatment with rituximab plus methotrexate on patient-reported outcomes in patients with active rheumatoid arthritis (RA) who experienced inadequate response to anti-tumor necrosis factor therapy.

METHODS

Patients with active RA were randomly assigned to rituximab (1,000 mg on days 1 and 15) or placebo. The primary end point was the proportion of patients with an American College of Rheumatology 20% response at week 24. Additional goals were to assess treatment effects on pain, fatigue, functional disability, health-related quality of life, and disease activity by comparing mean changes between groups. The analysis was conducted in the intent-to-treat population. The proportion of patients who achieved the minimum clinically important difference on the Health Assessment Questionnaire (HAQ) disability index (DI), Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F), and Short Form 36 (SF-36) was determined.

RESULTS

Rituximab patients had statistically significantly greater pain relief. The FACIT-F showed significantly greater improvement in rituximab patients than placebo patients from weeks 12 through 24. Mean improvement from baseline in functional disability (measured by the HAQ DI) was significantly greater in rituximab patients from weeks 8 to 24. The mean +/- SD change from baseline for the SF-36 Physical Component Score was 6.64 +/- 8.74 for rituximab patients and 1.48 +/- 7.32 for placebo patients (P < 0.0001). The mean change from baseline for the SF-36 Mental Component Score was 5.32 +/- 12.41 for rituximab patients and 2.25 +/- 12.23 for placebo patients (P = 0.0269).

CONCLUSION

Rituximab produced rapid, clinically meaningful, and statistically significant improvements in patient-reported pain, fatigue, functional disability, health-related quality of life, and disease activity. These effects were sustained throughout the study.

Inflammation and breast cancer. Balancing immune response: crosstalk between adaptive and innate immune cells during breast cancer progression

Recent insights into the molecular and cellular mechanisms underlying cancer development have revealed that immune cells functionally regulate epithelial cancer development and progression. Moreover, accumulated clinical and experimental data indicate that the outcome of an immune response toward an evolving breast neoplasm is largely determined by the type of immune response elicited. Acute tumor-directed immune responses involving cytolytic T lymphocytes appear to protect against tumor development, whereas immune responses involving chronic activation of humoral immunity, infiltration by Th2 cells, and protumor-polarized innate inflammatory cells result in the promotion of tumor development and disease progression. Herein we review this body of literature and summarize important new findings revealing the paradoxical role of innate and adaptive leukocytes as regulators of breast carcinogenesis.

Safety and efficacy of additional courses of rituximab in patients with active rheumatoid arthritis: an open-label extension analysis

OBJECTIVE

To determine the safety and efficacy of additional courses of rituximab in patients with rheumatoid arthritis (RA).

METHODS

An open-label extension analysis of RA patients previously treated with rituximab was conducted. Patients who had participated in any of 3 double-blind trials were eligible for additional courses (2 infusions of 1,000 mg given 2 weeks apart) if they exhibited a swollen joint count and tender joint count of > or =8 with > or =16 weeks elapsing after the previous course. Safety was assessed in patients receiving all or a portion of a rituximab course. Efficacy was assessed 24 weeks after each course, using the American College of Rheumatology 20% criteria for improvement (ACR20), ACR50, ACR70, European League Against Rheumatism (EULAR) response criteria, Disease Activity Score in 28 joints, the disability index of the Health Assessment Questionnaire, and Short Form 36 scores, stratified according to prior tumor necrosis factor (TNF) inhibitor exposure.

RESULTS

A total of 1,039 patients received > or =1 course of rituximab. Of these, 570 received 2 courses, 191 received 3 courses, and 40 received 4 courses, for a total of 1,669 patient-years. Irrespective of prior TNF inhibitor exposure, ACR20 responses were comparable at week 24 after course 1 and at week 24 after course 2 (65% versus 72%), as were ACR50 and ACR70 responses. EULAR moderate/good responses were also comparable in course 2 relative to course 1 (88% versus 79%), with EULAR remission occurring in a 2-fold higher proportion of patients after course 2 than after course 1 (13% versus 6%). The most common adverse events, which were mild-to-moderate acute infusion-related events, decreased with each course. The serious infection rate after course 1 (5.1 per 100 patient-years) remained stable through additional courses. The proportion of patients with circulating IgM and IgG levels below the lower limit of normal (LLN) increased with subsequent courses; however, serious infection rates in these patients (5.6 per 100 patient-years in patients with low IgM levels and 4.8 per 100 patient-years in patients with low IgG levels were comparable with those in patients with immunoglobulin levels above the LLN (4.7 per 100 patient-years). Patients with human antichimeric antibody (9.2%) did not exhibit decreasing efficacy or present additional safety concerns.

CONCLUSION

These findings indicate that patients treated with repeated courses of rituximab have sustained clinical responses with no new adverse events.

Identification of CD36 as a new surface marker of marginal zone B cells by transcriptomic analysis

Follicular (FO) B cells and marginal zone (MZ) B cells belong to the mature B cell population in spleen of mice. To identify new surface markers of these mature B cell subsets, we compared gene expression profiles of FO and MZ B cells by DNA microarray using FACS-sorted mouse FO and MZ B cells. From 14,000 mouse genes, 27 membrane proteins were expressed mainly in MZ B cells while another 22 membrane proteins expressed largely in FO B cells. Using FACS analysis, we identified that CD36, CD68, and CD49e were expressed on MZ B cells but not on FO B cells. In addition, using semi-quantitative PCR, we found that the mRNA of CD131 were much more abundant in MZ B cells. These results revealed new phenotypic properties of MZ and FO B cells, and would facilitate further studies in the differentiation and functions of these mature B cells.

Rituximab for rheumatoid arthritis refractory to anti–tumor necrosis factor therapy: Results of a multicenter, randomized, double-blind, placebo-controlled, phase III trial evaluating primary efficacy and safety at twenty-four weeks

OBJECTIVE

To determine the efficacy and safety of treatment with rituximab plus methotrexate (MTX) in patients with active rheumatoid arthritis (RA) who had an inadequate response to anti-tumor necrosis factor (anti-TNF) therapies and to explore the pharmacokinetics and pharmacodynamics of rituximab in this population.

METHODS

We evaluated primary efficacy and safety at 24 weeks in patients enrolled in the Randomized Evaluation of Long-Term Efficacy of Rituximab in RA (REFLEX) Trial, a 2-year, multicenter, randomized, double-blind, placebo-controlled, phase III study of rituximab therapy. Patients with active RA and an inadequate response to 1 or more anti-TNF agents were randomized to receive intravenous rituximab (1 course, consisting of 2 infusions of 1,000 mg each) or placebo, both with background MTX. The primary efficacy end point was a response on the American College of Rheumatology 20% improvement criteria (ACR20) at 24 weeks. Secondary end points were responses on the ACR50 and ACR70 improvement criteria, the Disease Activity Score in 28 joints, and the European League against Rheumatism (EULAR) response criteria at 24 weeks. Additional end points included scores on the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F), Health Assessment Questionnaire (HAQ) Disability Index (DI), and Short Form 36 (SF-36) instruments, as well as Genant-modified Sharp radiographic scores at 24 weeks.

RESULTS

Patients assigned to placebo (n = 209) and rituximab (n = 311) had active, longstanding RA. At week 24, significantly more (P < 0.0001) rituximab-treated patients than placebo-treated patients demonstrated ACR20 (51% versus 18%), ACR50 (27% versus 5%), and ACR70 (12% versus 1%) responses and moderate-to-good EULAR responses (65% versus 22%). All ACR response parameters were significantly improved in rituximab-treated patients, who also had clinically meaningful improvements in fatigue, disability, and health-related quality of life (demonstrated by FACIT-F, HAQ DI, and SF-36 scores, respectively) and showed a trend toward less progression in radiographic end points. Rituximab depleted peripheral CD20+ B cells, but the mean immunoglobulin levels (IgG, IgM, and IgA) remained within normal ranges. Most adverse events occurred with the first rituximab infusion and were of mild-to-moderate severity. The rate of serious infections was 5.2 per 100 patient-years in the rituximab group and 3.7 per 100 patient-years in the placebo group.

CONCLUSION

At 24 weeks, a single course of rituximab with concomitant MTX therapy provided significant and clinically meaningful improvements in disease activity in patients with active, longstanding RA who had an inadequate response to 1 or more anti-TNF therapies.

Rituximab, anti-CD20, induces in vivo cytokine release but does not impair ex vivo T-cell responses

Pre-formed HLA antibodies (Ab), reported as panel-reactive antibody (PRA), prolong transplant waiting time. We hypothesized that rituximab (RIT) could reduce PRA via B-cell depletion. As part of a Phase I study of single RIT dose, we studied in vivo and ex vivo effects on T-cell immune responses. Nine subjects (n = 3) were treated at 50, 150, and 375 mg/m(2). Serum interleukin-1alpha (IL-1alpha), IL-6, IL-12, tumor necrosis factor beta (TNF-beta), and interferon-gamma (IFN-gamma) were measured by enzyme-linked immunosorbent assay (ELISA). T-cell function was monitored with T-cell proliferation assays. IL-6 levels rose in eight patients (7.15 +/- 4.38 pg/mL to 86.22 +/- 77.08, p = 0.021). The high-dose group had detectable TNF-betapost rituximab infusion (874.7 +/- 1466.5 pg/mL). There was no decline in T-cell proliferation in response to phytohemagglutinin or allogeneic lymphocyte stimuli. Stimulation indices in the presence of both concentrations of tetanus toxoid rose significantly at 4 weeks.

AML1/Runx1 recruits calcineurin to regulate granulocyte macrophage colony-stimulating factor by Ets1 activation

Acute myeloid leukemia 1 (AML1), also denoted Runx1, is a transcription factor essential for hematopoiesis, and the AML1 gene is the most common target of chromosomal translocations in human leukemias. AML1 binds to sequences present in the regulatory regions of a number of hematopoiesis-specific genes, including certain cytokines such as granulocyte macrophage colony-stimulating factor (GM-CSF) up-regulated after T cell receptor stimulation. Here we show that both subunits of the Ca(2+)/calmodulin-dependent protein phosphatase calcineurin (CN), which is activated upon T cell receptor stimulation, interact directly with the N-terminal runt homology domain-containing part of AML1. The regulatory CN subunit binds AML1 with a higher affinity and in addition also interacts with the isolated runt homology domain. The related Runx2 transcription factor, which is essential for bone formation, also interacts with CN. A constitutively active derivative of CN is shown to activate synergistically the GM-CSF promoter/enhancer together with AML1 or Runx2. We also provide evidence that relief of the negative effect of the AML1 sites is important for Ca(2+) activation of the GM-CSF promoter/enhancer and that AML1 overexpression increases this Ca(2+) activation. Both subunits of CN interact with AML1 in coimmunoprecipitation analyses, and confocal microscopy analysis of cells expressing fluorescence-tagged protein derivatives shows that CN can be recruited to the nucleus by AML1 in vivo. Mutant analysis of the GM-CSF promoter shows that the Ets1 binding site of the promoter is essential for the synergy between AML1 and CN in Jurkat T cells. Analysis of the effects of inhibitors of the protein kinase glycogen synthase kinase-3beta and in vitro phosphorylation/dephosphorylation analysis of Ets1 suggest that glycogen synthase kinase-3beta-phosphorylated Ets1 is a target of AML1-recruited CN phosphatase at the GM-CSF promoter.

HIV-gp160 modulates differentially the production in vitro of IgG, IgA and cytokines by blood and tonsil B lymphocytes from HIV-negative individuals

HIV1-gp160 holds promises in anti-HIV vaccinal strategies. However, this molecule has been described to exhibit superantigenic activities. The present study aimed at examining the effect(s) of HIV1-gp160 on human B cells and in particular on B cells originating from HIV- donors. We purified human B cells of various origins, i.e. from blood and from tonsils (representing a mucosal-type origin), and we tested these cells (stimulated with a polyclonal B cell activator, interleukin (IL)-2 and IL-10 as cytokines, and recombinant HIV1-gp160) for the production of IgG and IgA in an in vitro model. Gp160 induced significantly less total IgG by blood - but not tonsil-originating - B cells and did not affect total IgA production. Further, HIV1-gp160 up-regulated IL-2-, IL-4- and IL-10-mRNA levels in stimulated blood B cells (these cytokines are known to be active on B cell activation and differentiation). Interestingly, HIV1-gp160 also up-regulated IL-1beta-, transforming growth factor (TGF)-beta-, interferon (IFN)-gamma- and IL-12-mRNA levels in stimulated mucosal-type, tonsil-originating, B cells. As these latter cytokines are involved in proinflammatory activities, HIV-gp160 delivery at the mucosal sites would be compatible with an adjuvant activity.

Calcium regulation of GM-CSF by calmodulin-dependent kinase II phosphorylation of Ets1

The multipotent cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) is involved in particular in the physiological response to infection and in inflammatory responses. GM-CSF is produced by many cell types, including T lymphocytes responding to T-cell receptor activation and mantle zone B lymphocytes. B-cell receptor and T-cell receptor activation generates two major signals: an increase in intracellular Ca(2+) concentration and a protein kinase cascade. Previous studies have shown that the Ca(2+)/calmodulin-dependent phosphatase calcineurin mediates stimulation of GM-CSF transcription in response to Ca(2+). In this study, we show that Ca(2+) signaling also regulates GM-CSF transcription negatively through Ca(2+)/calmodulin-dependent kinase II (CaMK II) phosphorylation of serines in the autoinhibitory domain for DNA binding of the transcription factor Ets1. Wild-type Ets1 negatively affects GM-CSF transcription on Ca(2+) stimulation in the presence of cyclosporin A, which inhibits calcineurin. Conversely, Ets1 with mutated CaMK II target serines showed an increase in transactivation of the GM-CSF promoter/enhancer. Moreover, constitutively active CaMK II inhibited transactivation of GM-CSF by wild-type Ets1 but not by Ets1 with mutated CaMK II sites. Mutation of CaMK II target serines in Ets1 also relieves inhibition of cooperative transactivation of GM-CSF with the Runx1/AML1 transcription factor. In addition, the Ca(2+)-dependent phosphorylation of Ets1 reduces the binding of Ets1 to the GM-CSF promoter in vivo.

Novel diversity in IL-4-mediated responses in resting human naive B cells versus germinal center/memory B cells

Recent studies have defined several phenotypic and molecular changes associated with the maturation of naive human B cells within the milieu of germinal centers. Although naive B cells serve as natural precursors to germinal center (GC)/memory (M) subpopulations, little is known about the physiological requirements for the survival of the naive B cell pool in the absence of cell-cell contact or Ag-mediated activation. Because IL-4 induces expression of several membrane receptors such as CD23 which are uniquely present on resting human naive B lymphocytes, we hypothesized that these cells might be intrinsically programmed to respond to IL-4 in the absence of cell division. Using buoyant density-dependent isolation and further enrichment by negative/positive selection of human naive and GC/M subpopulations, we characterized cytokine receptor moieties on these cells and analyzed their survival and growth in the presence of IL-4 or IL-10. Resting naive B cells expressed significantly higher IL-4 receptor alpha-chain on their cell surface than the combined GC/M subpopulation. The IL-10 receptor and the IL-2 receptor gammac chain were almost equally expressed on both subpopulations. When cultured in vitro, the addition of IL-4, but not IL-10, protected naive B cells from apoptosis in the absence of activation and growth. However, IL-4 exerted no such effect on resting GC/M B cells. These data support the hypothesis that IL-4 plays a pivotal role in the survival and maintenance of resting human naive B cells.

Granulocyte-macrophage colony-stimulating factor as an autocrine survival factor for mature normal and malignant B lymphocytes

The role of GM-CSF in B cell (patho)physiology is unclear. Although B cells can respond to GM-CSF, there is controversy concerning the extent to which various resting and activated B cell types can themselves produce this cytokine, and the possibility that it can function in an autocrine fashion has not previously been considered. The aim of the present study was to address these issues using hairy cells (HCs) and chronic lymphocytic leukemia cells, two intrinsically activated mature malignant B cell types (with activation being more uniform and more pronounced in HCs). Normal B cells were used for comparison. Using a number of techniques, we demonstrated the constitutive production of GM-CSF by all three cell types and showed that the cytokine was biologically active. GM-CSF mRNA and protein were increased after cell activation by PMA, and constitutive production of the cytokine was highest in HCs, suggesting that the level of GM-CSF production is influenced by cell activation. Because GM-CSF is known to be antiapoptotic for myeloid cells, we used blocking anti-GM-CSF Abs to examine the contribution of autocrinely produced cytokine to cell survival. The Abs produced marked reduction in the in vitro survival of HCs, chronic lymphocytic leukemia cells, and normal B cells by promoting apoptosis. Taken together, these findings suggest that, in combination with other known rescue factors, autocrinely produced GM-CSF may contribute to normal and malignant B cell survival in vivo.

Neoplastic cell activation and proliferative response to CD40-ligand characterize recurrent leukemic bouts in an unusual case of low grade lymphoma

Spontaneous fluctuations in activity of low-grade B cell lymphomas are common but not understood. An explanation may be offered by studying an atypical SLL/CLL case characterized by recurrent cycles of leukemic phase alternating with spontaneous remission (1). During remissions, residual IgMkappa+ leukemic cells exhibited resting phenotype, low proliferative response to CD4O-ligand and delayed apoptosis. In contrast, the acute phase counterparts were phenotypically activated, underwent rapid apoptosis in culture and proliferated extensively in response to membrane-anchored CD40-ligand. Transient bursts of serum TNFalpha and IL-10 preceded the acute phases, which were characterized by the co-existence of CD40-ligand+ T lymphocytes and lymphoma cells in the bone marrow. Based on ex-vivo and in-vitro data, we suggest that changes in the lymphoma milieu affect the neoplastic cell activation status, rate of proliferation in response to activated T cells and rate of apoptosis. These responses may underlie both the induction and spontaneous regression of the acute phases in this unique lymphoma. Our findings raise the possibility that part of this mechanism may have evolved during transformation of indolent common CLL to its more aggressive form.

Detection of Functional Platelet-Activating Factor Receptors on Human Tonsillar B Lymphocytes

Although platelet-activating factor (PAF) receptors have been found on B lymphoblastoid cell lines, the action of PAF on freshly isolated human B cells has not been clearly demonstrated. Using a sensitive semiquantitative reverse-transcriptase PCR, we have found PAF receptor mRNA expressed by tonsillar B lymphocytes, but little in T lymphocytes. Examination of Percoll-fractionated tonsillar B cells indicated that the low density (primarily germinal center cells) and medium density fractions had approximately twofold more PAF receptor mRNA relative to the high density fraction. PAF (10−7 M) stimulated increases in intracellular Ca2+ that were consistently higher in the low and medium density B lymphocytes compared with high density cells. The PAF receptor antagonist Web 2170 inhibited this. Addition of PAF, but not lyso- or enantio-PAF, induced four- to sixfold greater synthesis of IgM and IgG in low and medium density cells compared with unstimulated controls, but had little effect on Ig production by high density cells. To investigate how PAF may influence Ig synthesis, PAF-stimulated B cells were examined for production of the Th2-type cytokines IL-4 and IL-13. PAF induced IL-4 and IL-13 mRNA expression in 17% of CD20+ cells, and IL-4 was detected in cell supernatants after 48–72 h of culture. Together, these data strongly suggest that functional PAF receptors are expressed on B cells in tonsils.

Mature follicular dendritic cell networks depend on expression of lymphotoxin beta receptor by radioresistant stromal cells and of lymphotoxin beta and tumor necrosis factor by B cells

The formation of germinal centers (GCs) represents a crucial step in the humoral immune response. Recent studies using gene-targeted mice have revealed that the cytokines tumor necrosis factor (TNF), lymphotoxin (LT) alpha, and LTbeta, as well as their receptors TNF receptor p55 (TNFRp55) and LTbetaR play essential roles in the development of GCs. To establish in which cell types expression of LTbetaR, LTbeta, and TNF is required for GC formation, LTbetaR-/-, LTbeta-/-, TNF-/-, B cell-deficient (BCR-/-), and wild-type mice were used to generate reciprocal or mixed bone marrow (BM) chimeric mice. GCs, herein defined as peanut agglutinin-binding (PNA+) clusters of centroblasts/centrocytes in association with follicular dendritic cell (FDC) networks, were not detectable in LTbetaR-/- hosts after transfer of wild-type BM. In contrast, the GC reaction was restored in LTbeta-/- hosts reconstituted with either wild-type or LTbetaR-/- BM. In BCR-/- recipients reconstituted with compound LTbeta-/-/BCR-/- or TNF-/-/BCR-/- BM grafts, PNA+ cell clusters formed in splenic follicles, but associated FDC networks were strongly reduced or absent. Thus, development of splenic FDC networks depends on expression of LTbeta and TNF by B lymphocytes and LTbetaR by radioresistant stromal cells.