B-1 cells produce insulin and abrogate experimental streptozotocin-induced diabetes.

The participation of B-1 cells in a murine model of spontaneous diabetes has been recently reported. Here, we describe the role of B-1 cells in streptozotocin (STZ) induced diabetes in mice. We demonstrated that XID (B-1 cell-deficient) mice are more susceptible to STZ treatment than WT mice, as evidenced by their higher blood glucose level in response to STZ. Unexpectedly, the XID mice that were i.p. transferred with purified B-1 cells, either before or after the STZ treatment, did not develop diabetes. These cell transfers provided long-lasting protection for the XID mice against STZ-induced diabetes, suggesting that B-1 cells play an important role in the experimental diabetes pathobiology. We also showed that B-1 cell culture supernatants were able to regulate the blood glucose level of the diabetic XID mice, and we identified insulin-producing cells when B-1 cells were differentiated in B-1 cell-derived phagocyte in vitro. These findings provide a novel role for B-1 cells in metabolic processes, presenting a new mechanism to explain the pathogenesis of diabetes and a possible therapeutical target.

CD8 T lymphocytes from B-1 cell-deficient mice down-regulates fungicidal activity of macrophages challenged with E. Cuniculi.

BACKGROUND: Encephalitozoon cuniculi is an opportunistic intracellular pathogen that establishes a balanced relationship with immunocompetent individuals depending on the activity of their CD8+ T cells lymphocytes. However, lower resistance to experimental infection with E. cuniculi was found in B-1 deficient mice (Xid), besides increased the number of CD8 T lymphocytes. Here, we evaluated the profile of CD8+ T lymphocytes from Balb/c wild-type (WT) or Balb/c Xid mice (with B-1 cell deficiency) on the microbicidal activity of macrophages challenged with E. cuniculi. METHODS: Naïve CD8 T lymphocytes from WT or Xid mice uninfected and primed CD8 T lymphocytes from WT or Xid mice infected with E cuniculi were co-cultured with macrophages previously challenged with E. cuniculi. We evaluated macrophages viability and microbicidal activity, and CD8 T lymphocytes viability and presence of activating molecules (CD62L, CD69, and CD107a). RESULTS: Macrophages co-cultured with naïve CD8 T lymphocytes from WT demonstrated high microbicidal activity. Naïve CD8 T lymphocytes obtained from WT mice had a higher expression of CD69 and LAMP-1-activating molecules compared to Xid CD8+ T lymphocytes. Primed CD8 T lymphocytes from Xid mice proliferated more than those from WT mice, however, when the expression of the activating molecule CD69 associated with the expression of CD62L was kept low. In conclusion, naïve CD8+ T lymphocytes from Xid mice, deficient in B-1 cells, they had reduced expression of activation molecules and cytotoxic activity.

Mice with genetic and induced B-cell deficiency as a model for disseminated encephalitozoonosis.

Encephalitozoon cuniculi, an intracellular pathogen, lives in a balanced relationship with immunocompetent individuals based on the activity of T lymphocytes. We previously highlighted the greater susceptibility of B-1 cell-deficient mice (XID mice) to encephalitozoonosis. This study aimed to develop a model of disseminated and severe encephalitozoonosis in mice with combined immunodeficiency to elucidate the role of B cells. To address this objective, cyclophosphamide (Cy)-treated BALB/c and XID mice were inoculated with E. cuniculi, followed by the evaluation of the immune response and histopathological lesions. Immunosuppressed BALB/c mice manifested no clinical signs with an increase in the populations of T lymphocytes and macrophages in the spleen. Immunosuppressed and infected XID mice revealed elevated T cells, macrophages populations, and pro-inflammatory cytokines levels (IFN-γ, TNF-α, and IL-6) with the presence of abdominal effusion and lesions in multiple organs. These clinical characteristics are associated with extensive and severe encephalitozoonosis. The symptoms and lesion size were reduced, whereas B-2 and CD4+ T cells populations were increased in the spleen by transferring B-2 cells adoptive to XID mice. Moreover, B-1 cells adoptive transfer upregulated the peritoneal populations of B-2 cells and macrophages but not T lymphocytes and decreased the symptoms. Herein, we speculated the consistency in the development of severe and disseminated encephalitozoonosis in mice with genetic deficiency of Bruton's tyrosine kinase (Btk) associated with Cy immunosuppression develop with that of the models with T cell deficiency. Taken together, these data emphasized the crucial role of B cells in the protective immune response against encephalitozoonosis.

B-1 cells upregulate CD8 T lymphocytes and increase proinflammatory cytokines serum levels in oral encephalitozoonosis.

Microsporidia are intracellular pathogens that cause severe disease in immunocompromised humans and animals. We recently demonstrated that XID mice are more susceptible to Encephalitozoon cuniculi infection by intraperitoneal route, evidencing the role of B-1 cells in resistance against infection. The present study investigated the resistance and susceptibility against E. cuniculi oral infection, including the role of B-1 cells. BALB/c and BALB/c XID (B-1 cells deficient) mice were orally infected with E. cuniculi spores. No clinical symptoms were observed in infected animals; histopathology showed lymphoplasmocytic enteritis with degeneration of the apexes of the villi in all infected groups. Higher parasite burden was observed in infected BALB/c XID mice. In the spleen and peritoneum, all infected mice showed a decrease of lymphocytes, including CD8+ T cells, mostly in infected BALB/c XID mice. Adoptive transfer of B-1 cells (XID + B-1) was associated with a lower parasite burden. Pro-inflammatory cytokines (IFN-γ, TNF-α and IL-6) increased mostly in infected XID + B1 mice. Together, the present results showed that BALB/c XID mice infected by the oral route were more susceptible to encephalitozoonosis than BALB/c mice, demonstrating the B-1 cells importance in the control of the immune response against oral E. cuniculi infection.

B-1 cell decreases susceptibility to encephalitozoonosis in mice.

Encephalitozoon cuniculi is an opportunist intracellular pathogen of mammals. The adaptive immune response is essential to eliminate E. cuniculi, but evidence is mounting that the response initiated by the innate immune response may ultimately define whether or not the parasite can survive. B-1 cells may act as antigen-presenting cells or differentiate into phagocytes, playing different roles in many infection models. However, the role of these cells in the dynamics of Encephalitozoon sp. infections is still unknown. To investigate the role of B-1 cells in E. cuniculi infection, BALB/c and BALB/c XID (B-1 cells deficient) mice were infected with E. cuniculi spores. Cytometric analyses of peritoneal cells showed that B-1 cells and macrophages increased significantly in infected BALB/c mice compared to uninfected controls. Despite the increase in the number of CD4+ and CD8+ lymphocytes in XID mice, these animals were more susceptible to infection as evidenced histologically with more prominent inflammatory lesions and parasite burden. Pro-inflammatory cytokines increased in both infected BALB/c and BALB/c XID mice. To confirm B-1 cells role in encephalitozoonosis, we adoptively transferred B-1 cells to BALB/c XID mice and this group showed few symptoms and microscopic lesions, associated with an increased in cytokines. Together, these results suggest that B-1 cells may increase the resistance of BALB/c mice to encephalitozoonosis, evidencing for the first time the important role of B-1 lymphocytes in the control of microsporidia infection.

B-1 cell: the precursor of a novel mononuclear phagocyte with immuno-regulatory properties

Characterization of the origin, properties, functions and fate of cells is a fundamental task for the understanding of physiological and pathological phenomena. Despite the bulk of knowledge concerning the diverse characteristics of mammalian cells, some of them, such as B-1 cells, are still poorly understood. Here we report the results obtained in our laboratory on these cells in the last 10 years. After showing that B-1 cells could be cultured and amplified in vitro, a series of experiments were performed with these cells. They showed that B1 cells reside mostly in the peritoneal and pleural cavities, migrate to distant inflammatory foci, coalesce to form giant cells and participate in granuloma formation, both in vitro and in vivo. They are also able to present antigens to immunologically responsive cells and are endowed with regulatory properties. Further, we have also shown that these cells facilitate different types of infection as well as tumor growth and spreading. These data are presently reviewed pointing to a pivotal role that these cells may play in innate and acquired immunity.

A caracterização da origem, propriedades, funções e destino das células representam objetivo fundamental para a compreensão dos fenômenos fisiológicos e patológicos. Apesar da grande quantidade de conhecimentos relativos às diversas características das células de mamíferos, muitas delas, inclusive células B-1, são pouco entendidas. Depois de mostrar que as células B-1 podem ser cultivadas e amplificadas in vitro, uma série de experimentos visando esclarecer as propriedades dessas células puderam ser feitos em nosso laboratório nos últimos 10 anos. Assim, pudemos demonstrar que células B-1 residem principalmente nas cavidades peritoneal e pleural do camundongo, migram para focos inflamatórios distantes, coalescem para formar células gigantes e participam na formação de granulomas, tanto in vitro como in vivo. São também capazes de apresentar antígenos a células responsivas e são dotadas de propriedades imuno-regulatórias. Mostramos ainda que estas células favorecem diferentes tipos de infecções bem como o crescimento e metastatização tumoral. Esses resultados sugerem que células B-1 devem exercer papel central na imunidade como um todo.

Experimental lagochilascariosis in X-chromosome-linked immunodeficient mice / Lagochilascariose experimental em camundongos com imunodeficiência ligada ao cromossomo X

Lagochilascaris minor is the etiological agent of lagochilascariosis, a disease that affects the neck region and causes exudative abscesses, with eggs, adult parasites and L3/L4 larvae in the purulent exudates. Mice are now considered to be intermediate hosts for the parasite. To determine the pattern of infection in B1 cell-deficient mice, experimental lagochilascariosis was studied in BALB/c and X-chromosome-linked immunodeficient (xid) mice. BALB.xid-infected mice showed lower numbers of larvae. Third-stage larvae, fourth-stage larvae and adult parasites were found in both strains. BALB/c mice produced IgM, IgG, IgA and IgE against the crude extract and secreted/excreted antigens of the parasite. On the other hand, BALB.xid mice did not produce IgM and produced lower levels of IgG and IgA, and similar quantities of IgE.

Lagochilascaris minor é o agente etiológico da lagochilascariose, uma doença que afeta a região de pescoço provocando abscessos exudativos contendo ovos, parasitas adultos e larvas L3/L4 nos exudates purulentos. Atualmente, camundongos são considerados hospedeiros intermediários do parasita. Para determinar o padrão de infecção em camundongos deficientes de células B1, a lagochilascariose experimental foi estudada em camundongos BALB/c e em camundongos com imunodeficiência ligada ao cromossomo X (xid). Camundongos BALB.xid infectados mostraram menor número de larvas. Larvas L3, L4 e parasitas adultos foram encontrados em ambas as linhagens. Camundongos BALB/c produziram IgM, IgG, IgA e IgE contra o extrato bruto e antígenos secretados/excretados do parasita; por outro lado, camundongos BALB.xid não produziram IgM, produziram baixos níveis de IgG e IgA, e quantidades semelhantes de IgE.