Collectively, the present data show phagocytosis of nHZ by human monocytes induces inflammation-mediated expression and release of TIMP-1 through p38 MAPK- and NF-kB-dependent mechanisms, suggesting that in vivo nHZ-fed human monocytes may be a source for the high TIMP-1 serum levels found by Dietmann and colleagues in malaria patients. In this context, TIMP-1 levels are also related to disease severity. However, it remains unclear how TIMP-1 may exacerbate the clinical course in malaria patients. One major function of TIMP-1 is to counteract and modulate the numerous effects of MMP-9, which include degradation of the sub-endothelial basal lamina, modulation of the activity of several pro-inflammatory molecules, disruption of tight junctions, and impairment of haemostasis, all of which comprise key roles in CM. In this way it is attractive to hypothesize that increased TIMP-1 levels are actually protective rather than a risk factor in malaria prognosis, as they could contrast the potentially detrimental effects of nHZ-enhanced MMP-9. However, our results show that MMP-9/TIMP-1 stoichiometric ratios and total gelatinolytic activity measured in nHZ-fed monocyte supernatants were significantly 6bK higher than in controls, arguing against TIMP-1 ability to act as a protective factor in this context. Total gelatinolytic activity reflects the net overall activity of gelatinases and their endogenous inhibitors, but in the present model it should be noted that the activity is due solely to the net balance between MMP-9 and TIMP-1, as unfed and nHZ-fed human adherent monocytes do not release MMP-2 and TIMP-2 proteins. Therefore, these results suggest that nHZ-dependent induction of TIMP-1 expression and release is not 8-Chloroadenosine sufficient to counterbalance nHZ-enhanced MMP-9 levels released from human monocytes. Intriguingly, TIMP-1 could play a detrimental role through an MMP-independent mechanism. MMP-independent roles for TIMP-1 in biological processes include anti-apoptotic effects of TIMP-1 in several human cells, such as Burkitt��s lymphoma, breast epithelial cells, and cardiomyocytes. Recently CD63, a member of the tetraspanin family, was identified as a cellbinding partner for TIMP-1 in human mammary epithelial cells, and CD63 down-regulation with shRNA resulted in reduced TIMP-1 binding and restored cell apoptosis. Interestingly, nHZ-fed monocytes do not undergo apoptosis, despite increased inflammation and functional impairment. CD63 is constitutively expressed by human monocytes.