The role of protein kinases in antigen-activation of peripheral blood mononuclear cells of Schistosoma mansoni infected individuals

Assessment of Experimental Techniques That Facilitate Human Granuloma Formation in an In Vitro System: A Systematic Review

The process of granuloma formation is complex, and due to species differences, the validity of animal studies is somewhat questioned. Moreover, the large number of animals needed to observe the different stages of development also raises ethical questions. Therefore, researchers have explored the use of human peripheral blood mononuclear cells (PBMCs), a heterogeneous population of immune cells, in an in vitro model. This review included in vitro studies that focused on exposing PBMCs—from healthy, sensitized, or diseased individuals—to antigens derived from infectious agents—such as mycobacteria or Schistosoma spp.—or inorganic antigens—such as beryllium. The reviewed studies mainly explored how human in vitro granuloma models can contribute towards understanding the pathogenesis of granulomatous diseases, especially during the early stages of granuloma formation. The feasibility of granuloma modelling was thus largely assessed via experimental techniques including (1) granuloma scoring indices (GI), (2) cell surface markers and (3) cytokine secretion profiling. While granuloma scoring showed some similarities between studies, a large variability of culture conditions and endpoints measured have been identified. The lack of any standardization currently impedes the success of a human in vitro granuloma model.

Human peripheral blood mononuclear cells stimulated by Schistosoma mansoni antigens: association between protein tyrosine kinases, mitogen-activated protein kinases and cytokine production

Concerning schistosomiasis, little is known about the intracellular signaling response of human peripheral blood mononuclear cells (PBMC) to Schistosoma mansoni antigens. To understand the critical role of protein tyrosine kinases (PTKs) in PBMC activation by S. mansoni antigens, we investigated how inhibition of PTKs by genistein, a tyrosine kinase inhibitor, affects proliferation, cytokine production and activation of mitogen-activated protein kinases (MAPKs). Our studies showed that PTKs have an important role in proliferation of PBMC from chronic schistosomiasis patients as cells stimulated with S. mansoni soluble antigens in the presence of genistein had an impaired proliferation. In contrast, PTK inhibition failed to cause any effect on MAPKs activity. We also evaluated the cytokine production for interleukin (IL)-2, interferon gamma (IFN-gamma), and IL-10 in culture supernatants of PBMC treated with or without PTKs inhibitor. Our results show that PBMC from chronic patients produced a high amount of IL-10 when stimulated with soluble egg antigen preparation (SEA), however, the amount produced of IL-2 and IFN-gamma was not significant. In the presence of PTKs inhibitor only the production of IL-10 was decreased. The findings suggest that PTKs are involved on signal transduction pathway for PBMC activation, but may not be an absolute requirement for all signaling responses to S. mansoni antigens.

Role of nitric oxide on human schistosomiasis mansoni: upregulation of in vitro granuloma formation by N omega-nitro-L-arginine methyl ester

Over the past decade, nitric oxide has been intensely studied due to its relevance as a widespread intra- and intercellular messenger and as a cytotoxin released during several physiopathological events, including immunological reactions and inflammation. In the present paper, we investigate the effect of inhibition of NO synthesis, using an analogue of L-arginine, N omega-nitro-L-arginine methyl ester (L-NAME), on in vitro granulomatous formation of human peripheral blood mononuclear cells (PBMC) from Schistosoma mansoni-infected individuals. The results demonstrated that human PBMC are capable of in vitro NO production and that inhibition of its production through the addition of L-NAME is responsible for exacerbating granulomatous reaction. This L-NAME-induced granuloma enhancement (ranging from 30 to 65%) was measured using the granuloma index. Furthermore, we observed a general time-dependent increase in NO production during the period of cell culture (21 days) and an inverse relationship between nitrite detection and granuloma reactivity. Collectively, our results point to a possible regulatory role of NO on the development of granulomatous inflammation.