Jacy Gameiro

Thymic alterations in Plasmodium berghei-infected mice

The primary function of the thymus is to develop immature T-cells into cells that further in the periphery will be able to carry out immune functions. The Literature has shown that thymus can be a target for many pathogens and severe structural alterations take place in this organ during infectious diseases. Here, we investigated if thymus is also a target organ during experimental malaria infection by analyzing the presence of parasites inside the organ and histological alterations in thymuses from Plasmodium berghei NK65-infected BALB/c. After 14 days of infection, parasites were found inside the thymus that presented a profound atrophy with total loss of its architecture. We propose that the presence of parasites in the thymus induces histological modifications that alter the microenvironment, impairing by consequence the successful T cell development. Additional studies are currently being developed in our laboratory to verify if such thymic alterations can influence the systemic immune response to the parasite.

Thymic microenvironmental alterations in experimentally induced diabetes

Little is known about the immunologic consequences from endocrine changes observed in diabetes. Since a preserved thymic microenvironment is of critical importance for the T cell development and maturation, we have examined the thymus from alloxan-diabetic mice. An intense thymic atrophy accompanied by changes in histological pattern and in thymocyte subpopulations were observed in diabetic mice. Laminin and fibronectin, which are closely associated with thymocytes maturation, were evaluated, but, only laminin presented an altered distribution and density in thymuses from diabetes group. the expression of fibronectin and laminin receptors was found to be decreased in diabetic mice. There was also intense decrease in the expression of two important chemokines for thymus, CCL25 and CXCL12, and in the CCR9 (CCL25 receptor), but the expression of CXCR4 (CXCL12 receptor) did not drop on cells. However, no significant difference was observed in the in vitro thymocytes migratory capacity from diabetic mice. The results show significant alterations in thymus microenvironment in diabetes and offer insights for studies involving endocrine influences on lymphatic organs and T cell maturation.

Changes in cell migration‐related molecules expressed by thymic microenvironment during experimental Plasmodium berghei infection: consequences on thymocyte development

We previously showed alterations in the thymus during experimental infection with Plasmodium berghei. Such alterations comprised histological changes, with loss of cortical–medullary limits, and the intrathymic presence of parasites. As the combination of chemokines, adhesion molecules and extracellular matrix (ECM) is critical to appropriate thymocyte development, we analysed the thymic expression of ECM ligands and receptors, as well as chemokines and their respective receptors during the experimental P. berghei infection. Increased expression of ECM components was observed in thymi from infected mice. In contrast, down‐regulated surface expression of fibronectin and laminin receptors was observed in thymocytes from these animals. Moreover, in thymi from infected mice there was increased CXCL12 and CXCR4, and a decreased expression of CCL25 and CCR9. An altered thymocyte migration towards ECM elements and chemokines was seen when the thymi from infected mice were analysed. Evaluation of ex vivo migration patterns of CD4/CD8‐defined thymocyte subpopulations revealed that double‐negative (DN), and CD4+ and CD8+ single‐positive (SP) cells from P. berghei‐infected mice have higher migratory responses compared with controls. Interestingly, increased numbers of DN and SP subpopulations were found in the spleens of infected mice. Overall, we show that the thymic atrophy observed in P. berghei‐infected mice is accompanied by thymic microenvironmental changes that comprise altered expression of thymocyte migration‐related molecules of the ECM and chemokine protein families, which in turn can alter the thymocyte migration pattern. These thymic disturbances may have consequences for the control of the immune response against this protozoan.

Effect of low intensity helium-neon (HeNe) laser irradiation on experimental paracoccidioidomycotic wound healing dynamics.

The effect of HeNe laser on the extracellular matrix deposition, chemokine expression and angiogenesis in experimental paracoccidioidomycotic lesions was investigated. At days 7, 8 and 9 postinfection the wound of each animal was treated with a 632.8 nm HeNe laser at a dose of 3 J cm−2. At day 10 postinfection, the wounds were examined by using histologic and immunohistochemical methods. Results revealed that laser‐treated lesions were lesser extensive than untreated ones, and composed mainly by macrophages and lymphocytes. High IL‐1β expression was shown in the untreated group whereas in laser‐treated animals the expression was scarce. On the other hand, the expression of CXCL‐10 was found to be reduced in untreated animals and quite intensive and well distributed in the laser‐treated ones. Also, untreated lesions presented vascular endothelial growth factor (VEGF) in a small area near the center of the lesion and high immunoreactivity for hypoxia‐inducible factor‐1 (HIF‐1), whereas laser‐treated lesions expressed VEGF surrounding blood vessels and little immunoreactivity for HIF‐1. Laser‐treated lesions presented much more reticular fibers and collagen deposition when compared with the untreated lesion. Our results show that laser was efficient in minimizing the local effects observed in paracoccidioidomycosis and can be an efficient tool in the treatment of this infection, accelerating the healing process.

Cytokines Expressed in the Granulomatous Lesions in Experimental Paracoccidioidomycosis: Role in Host Protective Immunity and as Fungal Virulence Factor

Paracoccidioidomycosis (PCM) is a systemic granulomatous disease caused by the fungus Paracoccidioides brasiliensis (Pb). In the murine model of PCM, susceptible (S) mice develop disseminated disease with loose granulomas containing several viable fungi whereas resistant (R) mice show low fungal dissemination and encapsulated granulomas with few numbers of degenerated fungal cells. Here, we report the results of the expression of mRNA of these cytokines, as well as their distribution in the paracoccidioidomycotic granulomatous lesions and a semi quantitative score, that was correlated with the histological and biological data. Overall, our data show that the total area of granulomatous lesions and the relative areas of lesions containing Pb were, respectively, 1.2x and 1.9x more extensive in S than in the R mice. Also, the expression of IFN-γ and TNF-α mRNA was, respectively, 8x and 11x higher R mice and immunohistochemistry showed that the number of IFN-γ cells was 2.5x higher in R than in S mice. However, TNF-positivity was similar in the granulomas from S and R mice. In contrast, TGF-β mRNAs was 1.2x more expressed in S mice and this inhibitory cytokine was detected in higher concentration in the omental tissue from S mice. We hypothesize that the infection of R mice by Pb leads to the preferential synthesis of TNF-α and IFN-γ that promote macrophage activation, probably enhancing Pb killing and control of fungal dissemination, in parallel with the development of compact granulomatous lesions containing few fungi. On the other hand, the infection of S mice elicits preferential synthesis of TGF-β that deactivates macrophages and may inhibit Pb killing by macrophages, favoring fungal dissemination and formation of loose granulomatous lesions. The positivity to TGF-β in Pb yeast cells may consist in a virulence factor of Pb, inducing the suppressive milieu that favors fungal dissemination.

Thymic atrophy and fungal virulence during experimental paracoccidioidomycosis

The immunosuppression observed in systemic mycosis can be related to primary lymphoid organs damage. Thus, our laboratory has studied the effects of the Paracoccidioides brasiliensis infection on the thymus of mice. Here, thymuses of susceptible and resistant mice were evaluated after inoculation with highly and slightly virulent isolates of the fungus. All groups presented thymic atrophy, loss of corticomedullary delimitation and increase of apoptotic index. However, mice inoculated with high virulent strain showed earlier and stronger alterations suggesting that thymic atrophy can be directly related to the fungal virulence and to the immunosuppression.