The role of complement in the early phase of Leishmania (Leishmania) amazonensis infection in BALB/c mice

Complement-depleted and -non-depleted BALB/c mice were inoculated with Leishmania (Leishmania) amazonensis promastigotes into the hind footpad to study the role of the complement system in cutaneous leishmaniasis. Total serum complement activity was measured by hemolytic assay and C3 fragment deposit at the inoculation site was determined by direct immunofluorescence in the early period of infection, i.e., at 3, 24, 48 h and 7 days post-infection. The inflammatory reaction and the parasite burden were evaluated in the skin lesion at 7 and 30 days post-infection. Total serum complement activity decreased in the early phase of infection, from 3 to 24 h, in non-depleted mice compared to non-infected and non-depleted mice. C3 fragment deposit at the site of parasite inoculation was present throughout the period of infection in non-depleted mice. In contrast, no C3 fragment deposit was observed at the inoculation site in complement-depleted mice. Complement-depleted mice showed a significant decrease in the inflammatory response and a significant increase in the number of parasites (70.0 ± 5.3 vs 5.3 ± 1.5) at 7 days of infection (P < 0.05). A higher number of parasites were also present at 30 days of infection at the inoculation site of complement-depleted mice (78.5 ± 24.9 vs 6.3 ± 5.7). These experiments indicate that complement has an important role at the beginning of experimental cutaneous leishmaniasis caused by L. (L.) amazonensis by controlling the number of parasites in the lesion.

Serum cytokine profile in the subclinical form of visceral leishmaniasis

The factors determining the development or not of visceral leishmaniasis (VL) have not been completely identified, but a Leishmania-specific cellular immune response seems to play a fundamental role in the final control of infection. Few studies are available regarding the production of cytokines in the subclinical form of VL, with only the production of IFN-g and TNF-a known. The aim of the present study was to identify immunological markers for the oligosymptomatic or subclinical form of VL. A prospective cohort study was conducted on 784 children aged 0 to 5 years from an endemic area in the State of Maranhão, Brazil, between January 1998 and December 2001. During 30 consecutive months of follow-up, 33 children developed the oligosymptomatic form of the disease and 12 the acute form. During the clinical manifestations, serum cytokine levels were determined in 27 oligosymptomatic children and in nine patients with the acute form using a quantitative sandwich enzyme immunoassay. In the subclinical form of VL, variable levels of IL-2 were detected in 52.3 percent of the children, IL-12 in 85.2 percent, IFN-g in 48.1 percent, IL-10 in 88.9 percent, and TNF-a in 100.0 percent, with the last two cytokines showing significantly lower levels than in the acute form. IL-4 was not detected in oligosymptomatic individuals. Multiple discriminant analysis used to determine the profile or combination of cytokines predominating in the subclinical form revealed both a Leishmania resistance (Th1) and susceptibility (Th2) profile. The detection of both Th1 and Th2 cytokine profiles explains the self-limited evolution accompanied by the discrete alterations observed for the subclinical form of VL.

The role of natural killer cells in the early period of infection in murine cutaneous leishmaniasis

In order to study the role of natural killer (NK) cells during the early period of Leishmania infection, BALB/c mice were selectively and permanently depleted of NK cells by injection with 90Sr and subsequently infected with Leishmania (Leishmania) amazonensis (HSJD-1 strain). 90Sr is known to selectively deplete NK cells, leaving an intact T- and B-cell compartment and preserving the ability to produce both interferon alpha and IL-2. This method of depletion has advantages when compared with depletion using anti-NK cell monoclonal antibodies because the effect is permanent and neither activates complement nor provokes massive cell death. In the present study, after one month of treatment with 90Sr, the depletion of NK cells was shown by a more than ten-fold reduction in the cytotoxic activity of these cells: 2 x 106 spleen cells from NK-depleted animals were required to reach the same specific lysis of target cells effected by 0.15 x 106 spleen cells from normal control animals. The histopathology of the skin lesion at 7 days after Leishmania infection showed more parasites in the NK cell-depleted group. This observation further strengthens a direct role of NK cells during the early period of Leishmania infection

Epidermal dendritic cells in murine lupus

O lúpus eritematoso sistêmico (LES) é uma síndrome auto-imune multissistêmica. O acometimento cutâneo é freqüente e constitui manifestaçao clínica importante. O polimorfismo das lesoes cutâneas presume o envolvimento de diversos fatores etiopatogênicos. As células de Langerhans epidérmicas (CLs) têm funçoes imunorregulatórias importantes e participam de um modo decisivo na fisiopatologia de várias doenças dermatológicas inflamatórias, existindo evidência de seu envolvimento da patogênese da lesao cutânea lúpica. O camundongo F1 (NZB x NZW) um dos mais completos modelos experimentais de LES, nao desenvolve lesoes de pele. A ausência de dados na literatura referentes as CLs no camundongo F1 (NZB x NZW) motivou-lhes a realizar o presente estudo, que demonstrou, de forma original, a presença de CLs na epiderme do modelo F1, tanto por técnica citoquímica quanto por microscopia eletrônica de transmissao. Utilizando a técnica citoquímica da ATPase, estudamos as CLs no camundongo F1 (NZB x NZW) antes e após irradiaçao com luz ultravioleta B (UVB). As CLs no modelo F1 apresentaram-se em maior número e com alteraçoes morfológicas (dendritos curtos e menos ramificados) quando comparadas com os animais dos grupos-controles (BALB/c e C57BL/6). A irradiaçao UVB induziu alteraçoes morfológicas e reduçao no número das CLs do camundongo F1 em extensao semelhante ao observado no camundongo BALC/c. Nossos resultados sugerem possível alteraçao funcional nas CLs do camundongo F1 (NZB x NZW) e fornecem evidências de que estas células nao apresentam maior sensibilidade à luz UVB em comparaçao às de outras raças de camundongos. Estudos adicionais sao necessários para se testar possível associaçao entre essas alteraçoes fenotípicas das CLs e a ausência de manifestaçoes cutâneas nos camundongos F1 (NZB x NZW)

Comparative and sequential histopathology of plasmodium chabaudi-infected balb/c mice

1. Rodent experimental models have been useful to study severe malaria but few serial and controlled studies have been conducted. In the presente investigation, we describe the histopathology of lethal and non-lethal rodent malaria induced by Plasmodium berghei and P. chabaudi. P. berghei malaria shows a uniformly lethal course, while P. chabaudi malaria produces a non-lethal acute infection with recovery and periodical recurdescences. Sequential histopathological changes were also characterized in P. chabaudi malaria to determine the evolution of the lesions. 2. P. berghei-infected mice have a more severe organ involvement and lower blood regenerative changes than P. chabaudi-infected mice. Two patterns of organ involvement were observed by cimparing the two infections. The first is related to nonspecific parasitized red blood cell clearance by liver and spleen. The second is related to specific changes due to a specific parasite strain interaction with the host, such as those found in the lungs. 3. Sequential changes in P. chabaudi-infected mice were characterized by perihepatocytic reticulin fiber deposition during the recovery from infection, which faded in subsequent stages. Other organs had a similar regressive evolution, except splenic lymphoid tissue which underwent histological restoration or even hypertrophy after depletion in the acute stage. No brain or heart lesions were observed in either model during the acute and subsequent stages. 4. P. chabaudi infection, whose histopathology is described here for the first time, should be useful as a non-lethal experimental model to study the evolution of histological alterations in malaria