Dependency of B-1 Cells in the Maintenance of Splenic Interleukin-10 Producing Cells and Impairment of Macrophage Resistance in Visceral Leishmaniasis

Status of B-Lymphocyte Subsets and Their Homing Markers in Patients With Post-Kala-Azar Dermal Leishmaniasis

In visceral leishmaniasis, the Type II helper T cell predominance results in B cell modulation and enhancement of anti-leishmanial IgG. However, information regarding its dermal sequel, post-kala-azar dermal leishmaniasis (PKDL), remains limited. Accordingly, this study aimed to elucidate the B cell-mediated antibody-dependent/independent immune profiles of PKDL patients. In the peripheral blood of PKDL patients, immunophenotyping of B cell subsets was performed by flow cytometry and by immunohistochemistry at lesional sites. The functionality of B cells was assessed in terms of skin IgG by immunofluorescence, while the circulating levels of B cell chemoattractants (CCL20, CXCL13, CCL17, CCL22, CCL19, CCL27, CXCL9, CXCL10 and CXCL11) were evaluated by a multiplex assay. In patients with PKDL as compared with healthy controls, there was a significant decrease in pan CD19+ B cells. However, within the CD19+ B cell population, there was a significantly raised proportion of switched memory B cells (CD19+IgD-CD27+) and plasma cells (CD19+IgD-CD38+CD27+). This was corroborated at lesional sites where a higher expression of CD20+ B cells and CD138+ plasma cells was evident; they were Ki67 negative and demonstrated a raised IgG. The circulating levels of B cell chemoattractants were raised and correlated positively with lesional CD20+ B cells. The increased levels of B cell homing markers possibly accounted for their enhanced presence at the lesional sites. There was a high proportion of plasma cells, which accounted for the increased presence of IgG that possibly facilitated parasite persistence and disease progression.

Exploring the paradox of defense between host and Leishmania parasite

Leishmaniasis, a neglected tropical disease, still remains a global concern for the healthcare sector. The primary causative agents of the disease comprise diverse leishmanial species, leading to recurring failures in disease diagnosis and delaying the initiation of appropriate chemotherapy. Various species of the Leishmania parasite cause diverse clinical manifestations ranging from skin ulcers to systemic infections. Therefore, host immunity in response to different forms of infecting species of Leishmania becomes pivotal in disease progression or regression. Thus, understanding the paradox of immune arsenals during host and parasite interface becomes crucial to eliminate this deadly disease. In the present review, we have elaborated on the immunological perspectives of the disease and discussed primary host immune cells that form a defense line to counteract parasite infection. Furthermore, we also have shed light on the immune cells and effector molecules responsible for parasite survival in host lethal milieu/ environment. Next, we have highlighted recent molecules/compounds showing potent leishmanicidal activities pertaining to their pro-oxidant and immuno-modulatory mechanisms. This review addresses an immuno-biological overview of the factors influencing the parasitic disease, as this knowledge can aid in the unraveling/ identification of potential biomarkers, novel therapeutics, and vaccine candidates against leishmaniasis.

Immune Function in Critically Ill Septic Children

The inflammatory response in pediatric sepsis is highly dynamic and includes both pro- and anti-inflammatory elements that involve the innate and adaptive immune systems. While the pro-inflammatory response is responsible for the initial clinical signs and symptoms of sepsis, a concurrent compensatory anti-inflammatory response often results in an occult, but highly clinically relevant, form of acquired immunodeficiency. When severe, this is termed "immunoparalysis" and is associated with increased risks for nosocomial infection, prolonged organ dysfunction, and death. This review focuses on the pathophysiology and clinical implications of both over- and under-active immune function in septic children. Host-, disease-, and treatment-specific risk factors for immunoparalysis are reviewed along with immune phenotype-specific approaches for immunomodulation in pediatric sepsis which are currently the subject of clinical trials.

Modulation of Splenic B Cell Subsets during Experimental Leishmania donovani Infection in BALB/c Mice

Sodium antimonials are one of the major and common drugs used against visceral form leishmaniasis (VL). However, the development of drug resistance makes it difficult to manage this disease. Current work investigates the modulation of splenic B cells during experimental infection with antimony-sensitive and -resistant Leishmania donovani infection. Here we phenotypically characterized splenic B cell subsets in BALB/c mice infected with antimony drug-sensitive and -resistant VL strains using flow-cytometry method. In the splenocytes we noticed increased number of Transitional T3 B cells and B1a B cells in drug-resistant VL strain infection. Besides, we also observed alteration in Follicular B cell population of antimony-resistant strain infected mice. Drug-resistant strain induced secretion of elevated level of IL-10 from B1a B cells and IL-6 from Transitional T3 B cell subsets in the splenocytes. Purified splenic B cells from antimony drug-resistant strain infected mice showed decrease in the Lyn kinase gene expression compared to sensitive strain infected and uninfected mice. The current study provides insight into changes in host splenic B-cell subsets during experimental infection with antimony-sensitive and -resistant L. donovani in murine model.

ACTH4-10 protects the ADR-injured podocytes by stimulating B lymphocytes to secrete interleukin-10

OBJECTIVES

In the present study, we aimed to assess whether adrenocorticotropic hormone (ACTH) could protect the podocytes from adriamycin (ADR)-induced injury by stimulating B lymphocytes to secrete the associated cytokines.

METHODS

Proliferation assay was used to assess the proliferation and activity of podocytes. Enzyme-linked immunosorbent assay was used to examine the secretion of IL-10 and IL-4. TUNEL apoptosis detection kit was used to detect the apoptosis of podocytes. Real-time PCR and Western blotting analysis were used to examine the expressions of nephrin and podocin at the mRNA and protein levels.

RESULTS

Compared with the normal control group, the podocyte proliferation of ADR group was significantly inhibited. However, compared with the ADR group, the podocyte proliferation of the supernatant (1 µg/L, 10 µg/L or 100 µg/L ACTH_4-10) + ADR groups was generally increased, and the pro-proliferative effect of the supernatant containing 10 µg/L ACTH_4-10 was the highest. Moreover, we found that after B lymphocytes were intervened by 10 µg/L ACTH4-10, the IL-10 level in the cell supernatant was significantly elevated (p < 0.05). When anti-IL-10R was added, the podocyte proliferation of the supernatant (10 µg/L ACTH_4-10) + ADR group was significantly inhibited. Furthermore, the supernatant of B cells stimulated with 10 µg/L ACTH_4-10 could better decrease the apoptosis rate of injured podocytes and increase the expressions of nephrin and podocin at the mRNA and protein levels by elevating the secretion of IL-10.

CONCLUSION

Compared with ACTH_4-10, the supernatant of B cells stimulated with ACTH_4-10 could better protect the podocytes from ADR-induced injury by elevating the secretion of IL-10.

Infection by Leishmania (Leishmania) infantum chagasi causes intestinal changes B-1 cells dependent

Evaluating the histopathological and morphometric changes caused by Leishmania (Leishmania) infantum chagasi infection either in the presence or absence of B-1 cells. Wild-type Balb/c and XID mice were used. Half of XID mice received B-1 cells adoptive transfer (XID + B1). Five animals from each group were infected (Balb/c I, XID I and XID + B1 I), totalizing six groups (n = 5). After 45 days of infection, the ileum was collected for histological processing and analysis. After infection, the XID animals showed an increase in the thickness of the intestinal layers, in the depth and width of the crypt and in the villi width. However, the Balb/c I group showed a reduction in almost all these parameters, whereas the villi width was increased. The villi height decreased in the infected XID animals; however, it was increased in the XID + B1 I group. Leishmania (L) infantum chagasiinfection caused a decrease in the number of Paneth cells; however, their area was increased. Finally, goblet cells and enterocytes presented different change profiles among groups. This study showed that the parasite infection causes structural and histopathological alterations in the intestine. These changes might be influenced by the absence of B-1 cells.

How to B(e)-1 Important Cell During Leishmania Infection

B-1 cells are an innate-like population of B lymphocytes that are subdivided into B-1a and B-1b distinguished by the presence or absence of CD5, respectively. B-1 cells can act as regulatory B cells, are able to present antigen and produce IL-10. Leishmaniasis in humans is a complex of diseases caused by parasites of the genus Leishmania. More than 20 species can infect humans, with each species causing the development of different immunological responses in the host. Susceptibility is usually related to the production of anti-inflammatory cytokines while the production of Th1 cytokines is indicative of resistance. However, few studies have attempted to evaluate the role of B-1 cells during either the in vivo infection or in vitro interaction with Leishmania parasites. In vivo studies were performed using XID mice model, BALB/Xid mice have a mutation in the Bruton's tyrosine kinase, which is an important enzyme for developing B-1 and maturing B-2 lymphocytes leading to the presence of immature B-2 cells. Here, we compile these studies and assess the influence of B-1 cells on disease progression with different Leishmania species.

B-1 cell response in immunity against parasites

The peritoneal cavity has a microenvironment capable of promoting proliferation, differentiation, and activation of the resident cells and recruitment of blood cells through the capillary network involved in the peritoneum. Among the cells found in the peritoneal cavity, B-1 cells are a particular cell type that contains features that are not very well defined. These cells differ from conventional B lymphocytes (B-2) by phenotypic, functional, and molecular characteristics. B-1 cells can produce natural antibodies, migrate to the inflammatory focus, and have the ability to phagocytose pathogens. However, the role of B-1 cells in immunity against parasites is still not completely understood. Several experimental models have demonstrated that B-1 cells can affect the susceptibility or resistance to parasite infections depending on the model and species. Here, we review the literature to provide information on the peculiarities of B-1 lymphocytes as well as their interaction with parasites.

B-1 cell responses to infections

B-1 cells represent an innate-like early-developing B cell population, whose existence as an independent lymphocyte subset has been questioned in the past. Recent molecular and lineage tracing studies have not only confirmed their unique origins and differentiation paths, they have also provided a rationale for their distinctive functionalities compared to conventional B cells. This review summarizes our current understanding of B-1 cell development, and the activation events that regulate B-1 cell responses to self and foreign antigens. We discuss the unresolved question to what extent BCR engagement, that is, antigen-specificity versus innate signaling contributes to B-1 cell's participation in tissue homeostasis and immune defense as providers of 'natural' and antigen-induced antibody responses, and as cytokine-producing immune regulators.

Quantification of Leishmania Parasites in Murine Models of Visceral Infection

Visceral leishmaniasis (VL) is mainly caused by Leishmania donovani (India and East Africa), and Leishmania infantum (Mediterranean Basin and South America) infections. Although murine models of visceral infection lack the clinicopathological aspects of VL in humans, they have been proven useful at advancing our knowledge in the Leishmania field. Indeed, these models have been used not only to better understand the pathophysiology of the infection but also in drug and vaccine development. This chapter focuses on the protocols used to experimentally infect mice and to quantify parasite burdens in mice infected with L. infantum using limiting dilution methodology of target organs and whole-mouse in vivo imaging.

Brucella Downregulates Tumor Necrosis Factor-α to Promote Intracellular Survival via Omp25 Regulation of Different MicroRNAs in Porcine and Murine Macrophages

Brucella spp. impedes the production of pro-inflammatory cytokines by its outer membrane protein Omp25 in order to promote survival and immune evasion. However, how Omp25 regulates tumor necrosis factor (TNF-α) expression in different mammalian macrophages remains unclear. In this study, we investigated the potential mechanisms by which Omp25 regulates TNF-α expression and found that Omp25-deficient mutant of B. suis exhibited an enhanced TNF-α expression compared with wild-type (WT) B. suis, whereas ectopic expression of Omp25 suppressed LPS-induced TNF-α production at both protein and mRNA levels in porcine alveolar macrophages (PAMs) and murine macrophage RAW264.7 cells. We observed that Omp25 protein as well as WT B. suis upregulated miR-146a, -181a, -181b, and -301a-3p and downregulated TRAF6 and IRAK1 in both PAMs and RAW264.7 cells, but separately upregulates miR-130a-3p in PAMs and miR-351-5p in RAW264.7. The upregulation of miR-146a or miR-351-5p attenuated TNF-α transcription by targeting TRAF6 and IRAK1 at the 3' untranslated region (UTR), resulting in inhibition of NF-kB pathway, while upregulation of miR-130a-3p, -181a, or -301a-3p correlated temporally with decreased TNF-α by targeting its 3'UTR in PAMs or RAW264.7 cells. In contrast, inhibition of miR-130a-3p, -146a, -181a, and -301a-3p attenuated the inhibitory effects of Omp25 on LPS-induced TNF-α in PAMs, while inhibition of miR-146a, -181a, -301a-3p, and -351-5p attenuated the inhibitory effects of Omp25 in RAW264.7, resulting in an increased TNF-α production and decreased intracellular bacteria in both cells. Taken together, our results demonstrate that Brucella downregulates TNF-α to promote intracellular survival via Omp25 regulation of different microRNAs in porcine and murine macrophages.