Interleukin-4 Responsive Dendritic Cells Are Dispensable to Host Resistance Against Leishmania mexicana Infection.

IL-4 and IL-13 cytokines have been associated with a non-healing phenotype in murine leishmaniasis in L. mexicana -infected BALB/c mice as demonstrated in IL-4-/-, IL-13-/- and IL-4Rα-/- global knockout mouse studies. However, it is unclear from the studies which cell-type-specific IL-4/IL-13 signaling mediates protection to L. mexicana. Previous studies have ruled out a role for IL-4-mediated protection on CD4+ T cells during L. mexicana infections. A candidate for this role may be non-lymphocyte cells, particularly DCs, as was previously shown in L. major infections, where IL-4 production drives dendritic cell-IL-12 production thereby mediating a type 1 immune response. However, it is unclear if this IL-4-instruction of type 1 immunity also occurs in CL caused by L. mexicana, since the outcome of cutaneous leishmaniasis often depends on the infecting Leishmania species. Thus, BALB/c mice with cell-specific deletion of the IL-4Rα on CD11c+ DCs (CD11ccreIL-4Rα-/lox) were infected with L. mexicana promastigotes in the footpad and the clinical phenotype, humoral and cellular immune responses were investigated, compared to the littermate control. Our results show that CL disease progression in BALB/c mice is independent of IL-4Rα signaling on DCs as CD11ccreIL-4Rα-/lox mice had similar footpad lesion progression, parasite loads, humoral responses (IgE, IgG1, IgG 2a/b), and IFN-γ cytokine secretion in comparison to littermate controls. Despite this comparable phenotype, surprisingly, IL-4 production in CD11ccreIL-4Rα-/lox mice was significantly increased with an increasing trend of IL-13 when compared to littermate controls. Moreover, the absence of IL-4Rα signaling did not significantly alter the frequency of CD4 and CD8 lymphocytes nor their activation, or memory phenotype compared to littermate controls. However, these populations were significantly increased in CD11ccreIL-4Rα-/lox mice due to greater total cell infiltration into the lymph node. A similar trend was observed for B cells whereas the recruitment of myeloid populations (macrophages, DCs, neutrophils, and Mo-DCs) into LN was comparable to littermate IL-4Rα-/lox mice. Interestingly, IL-4Rα-deficient bone marrow-derived dendritic cells (BMDCs), stimulated with LPS or L. mexicana promastigotes in presence of IL-4, showed similar levels of IL-12p70 and IL-10 to littermate controls highlighting that IL-4-mediated DC instruction was not impaired in response to L. mexicana. Similarly, IL-4 stimulation did not affect the maturation or activation of IL-4Rα-deficient BMDCs during L. mexicana infection nor their effector functions in production of nitrite and arginine-derived metabolite (urea). Together, this study suggests that IL-4 Rα signaling on DCs is not key in the regulation of immune-mediated protection in mice against L. mexicana infection.

Systemic Treatment for Severe Atopic Dermatitis.

Atopic dermatitis (AD) is a chronic inflammatory, relapsing disease of the skin, characterized by intense pruritus, maculopapular or vesicular erythematous lesions and scaling, sometimes accompanied by oozing, crusts and/or lichenification that has a negative impact on patients' quality of life. Prevalence is higher in children, around 15%, and approximately 5% in adults. Before introducing systemic therapy, it is mandatory to review patients' adherence to the correct use of topical treatments (corticosteroids, calcineurin inhibitors or cresoborole) and/or phototherapy. Ensure that environmental measures are being taken care of, irritant or proven allergic substances are not in use and even if the diagnostic is correct. If all is being done and topical treatment with corticosteroid, emollients and phototherapy have not been sufficient to achieve a good control in AD of adults or children patients, it is time to consider systemic agents. Up to now, most of systemic treatments were based on immunosuppressive therapies, being cyclosporine A, the usually first choice for moderate-to-severe AD. Recently, biologic drugs have been developed and approved for AD, as dupilumab, and a whole new group of drugs is giving much hope for patients to have a better control of the disease with less side effects.

Immature dendritic cells generated from cryopreserved human monocytes show impaired ability to respond to LPS and to induce allogeneic lymphocyte proliferation.

Dendritic cells play a key role in the immune system, in the sensing of foreign antigens and triggering of an adaptive immune response. Cryopreservation of human monocytes was investigated to understand its effect on differentiation into immature monocyte-derived dendritic cells (imdDCs), the response to inflammatory stimuli and the ability to induce allogeneic lymphocyte proliferation. Cryopreserved (crp)-monocytes were able to differentiate into imdDCs, albeit to a lesser extent than freshly (frh)-obtained monocytes. Furthermore, crp-imdDCs had lower rates of maturation and cytokine/chemokine secretion in response to LPS than frh-imdDCs. Lower expression of Toll-like receptor 4 (at 24 and 48 h) and higher susceptibility to apoptosis in crp-imdDCs than in fresh cells would account for the impaired maturation and cytokine/chemokine secretion observed. A mixed leukocyte reaction showed that lymphocyte proliferation was lower with crp-imdDCs than with frh-imdDCs. These findings suggested that the source of monocytes used to generate human imdDCs could influence the accuracy of results observed in studies of the immune response to pathogens, lymphocyte activation, vaccination and antigen sensing. It is not always possible to work with freshly isolated monocytes but the possible effects of freezing/thawing on the biology and responsiveness of imdDCs should be taken into account.

Murine model of chronic L. (Viannia) panamensis infection: role of IL-13 in disease.

Leishmania (Viannia) organisms are the most prevalent etiologic agents of human cutaneous leishmaniasis in the Americas. Nevertheless, our knowledge of the immunological mechanisms exploited by L. (Viannia) organisms remains limited and the mechanisms underlying disease are not well understood. Here, we report the development of a BALB/c mouse model of L. (V.) panamensis infection that is able to reproduce chronic disease, with persistent infection and clinically evident lesions for over 1 year. The immune response of the mouse resembles that found for L. (V.) panamensis-infected patients with chronic and recurrent lesions, presenting a mixed Th1/Th2 response with the presence of TNF-α, IFN-γ, IL-10 and IL-13. Using immunodeficient mice, the critical role for IL-13 and/or IL-4Rα in determining susceptibility to chronic infection was evident. With the induction of healing in the immunodeficient mice, increases in IFN-γ and IL-17 were found, concomitant with parasite control and elimination. Specifically, increases in CD4(+) (but not CD8(+)) T cells producing IFN-γ were observed. These results suggest that IL-13 represents an important target for disease control of L. (V.) panamensis infection. This murine model should be useful to further understand the pathology associated with chronic disease and to develop methods for the treatment and prevention of leishmaniasis caused by L. (Viannia) parasites.

Sex-determined resistance against Leishmania mexicana is associated with the preferential induction of a Th1-like response and IFN-gamma production by female but not male DBA/2 mice.

Female DBA/2 mice are relatively resistant to infection with Leishmania mexicana compared with male mice. Following subcutaneous infection with 5 x 10(6) L. mexicana, amastigotes lesion growth in male and female DBA/2 mice was measured and the developing immune responses were monitored both in vitro and in vivo. Over the 10 week duration of the experiment all male DBA/2 mice developed rapidly growing non-healing lesions while female mice either developed no lesions whatsoever or developed smaller slower growing lesions than males. Both male and female mice produced parasite specific IgG2a during the course of the disease. However, significant titres of parasite specific IgG1 antibodies could be detected only in male mice indicating a Th2-influenced response in this sex. Furthermore, female mice, unlike male mice, developed significant parasite induced cutaneous delayed-type hypersensitivity footpad responses, indicating a Th1-influenced response in female mice. Although both male and female DBA/2 mice infected with L. mexicana displayed a significant increase in the number of cells in their draining lymph nodes at week 10 post-infection, no significant differences could be observed in the numbers of CD4+, CD8 + T cells as well as B cells between male and female DBA/2 mice. However. following in vitro stimulation, the lymph node cells from female mice displayed significantly higher antigen specific proliferative responses than the males and produced significant amounts of IFN-gamma which could not be detected in the equivalent culture supernatants from male mice. There were no significant differences in the levels of Th2-associated cytokines IL-4 and IL-5, produced by the lymph node cells of both sexes. Treatment of female DBA/2 mice with IFN-gamma neutralizing antibody following L. mexicana infection resulted in lesion growth equivalent to male mice. Conversely, intralesional injections of murine recombinant IFN-gamma significantly inhibited lesion growth in male mice.