berghei-infected mice, when compared with controls. We next evaluated the migratory responses of each CD4/CD8-defined thymocyte subset, under the same stimuli. We found that DN cells and CD4+ and CD8+ SP cells from P. berghei-infected MI-503 mice showed higher migratory activity than

controls (see data in Table 1). Rather surprisingly, the number of CD4+ CD8+ living migrating cells was consistently decreased when they derived from infected animals compared with controls. Last, and considering that migratory responses of thymocytes from infected mice were significantly higher than the corresponding controls, we evaluated the T-cell pool in the periphery, more specifically in the spleen. As depicted in Fig. 5, the numbers of immature thymocytes (DN subpopulation) Tigecycline were significantly increased in infected animals, as well as the numbers of CD4+ and CD8+ SP T-cell subsets. The interplay between thymoctes and the thymic microenvironment is modulated by a variety of proteins, like ECM components

and chemokines, and it has been considered of crucial importance to provide the correct signals to thymocyte migration and maturation.14,21 In this sense, it is reasonable to suppose that alterations in ECM elements and chemokines are implicated in thymic dysfunction. We have previously reported that P. berghei infection induces thymic atrophy with changes in its architecture that are characterized by loss of the cortico–medullary delimitation and massive depletion of thymocytes, mainly the DP subpopulation.5 In this paper we have described how thymic atrophy induced by malaria infection is also characterized by profound alterations in the expression of ECM components and chemokines, in such a way that thymocyte migration inside the thymus, which is an essential event for T-cell development, is severely compromised. The intrathymic contents of selected chemokines, CXCL12 and CCL25, as well as of the ECM proteins fibronectin

and laminin, were altered in thymi from infected animals compared with uninfected controls. These changes are similar to those described during acute murine infection by T. cruzi, the causative agent of Chagas’ disease.17,18 At least in relation to fibronectin, it is possible that the intrathymic contents in the remaining Phosphoglycerate kinase cortex of the thymic lobules may be related to the DP thymocyte death because this ECM protein was reported as being able to increase the incidence of death in these thymocyte subsets.22 Nevertheless a cause–effect relationship remains to be determined. In any case, the increase of fibronectin, laminin and CXCL12 and the decrease of CCL25 strongly indicate anomalies in thymocyte migration, as it had been found in T. cruzi-infected mice. We therefore defined the patterns of membrane expression of corresponding receptors, comparing normal with P. berghei-infected mice.