Lack of evidence for superantigen activity of Toxoplasma gondii towards human T cells

Toxoplasma gondii is an obligatory intracellular parasite whose life cycle may include man as an intermediate host. More than 500 million people are infected with this parasite worldwide. It has been previously reported that T. gondii contains a superantigen activity. The purpose of the present study was to determine if the putative superantigen activity of T. gondii would manifest towards human T cells. Peripheral blood mononuclear cells (PBMC) from individuals with no previous contact with the parasite were evaluated for proliferation as well as specific Vá expansion after exposure to Toxoplasma antigens. Likewise, PBMC from individuals with the congenital infection were evaluated for putative Vá family deletions in their T cell repertoire. We also evaluated, over a period of one year, the PBMC proliferation pattern in response to Toxoplasma antigens in patients with recently acquired infection. Some degree of proliferation in response to T. gondii was observed in the PBMC from individuals never exposed to the parasite, accompanied by specific Vá expansion, suggesting a superantigen effect. However, we found no specific deletion of Vá (or Valpha) families in the blood of congenitally infected individuals. Furthermore, PBMC from recently infected individuals followed up over a period of one year did not present a reduction of the Vá families that were originally expanded in response to the parasite antigens. Taken together, our data suggest that T. gondii does not have a strong superantigen activity on human T cells

Imunidade celular ao antígeno S empacientes com uveíte endógena / Cellular immune responses to S-antigen in endogenous uveitis

A auto-imunidade retiniana desempenha um papel na etiopatogenia de várias uveítes endógenas. Estudos experimentais e ensaios clínicos têm demonstrado a importância de antígenos retinianos, como o antígeno S (AgS), näo somente na patogenia mas também na elaboraçäo de estratégias de imunoterapia. O presente trabalho visa analisar o perfil da imunidade celular in vitro ao AgS e a dois de seus peptídeos relevantes, denominados M e G, em uma populaçäo brasileira com diagnóstico de uveíte por doença de Behçet (DB) (n=19), doença de Vogt-koyanagi-Harada (DVKH) (n=27) e vasculite da retina (n=5) acompanhados no serviço de uveíte do Hospital das Clínicas da Faculdade de Medicina da USP. Pacientes com DB sem uveíte (n=17) e 16 controles normais foram também analisados ..