The role of regulatory T cells in chronic and acute viral infections.

Regulatory T cells, a subset of CD4(+) T lymphocytes, play a pivotal role in the maintenance of the balance between the tissue-damaging and protective effects of the immune response. These cells have immunosuppressive function and have been intensely studied in the context of autoimmunity, cancer, allergies, asthma, and infectious diseases. Their role in chronic and persistent viral infections is well appreciated. In acute viral infections, the function of these cells is still unclear. The host and pathogen factors that control the generation and activity of regulatory T cells and the role of these cells in modulating expansion, contraction, and development of immune memory in acute respiratory virus infection need to be further elucidated.

Parvovirus B19 associated adult Henoch Schönlein purpura.

BACKGROUND: Parvovirus B19 has recently been implicated in various vasculitic syndromes including Henoch Schönlein purpura (HSP), Wegener's granulomatosis and microscopic polyarteritis. The association was established through serology, the identification of DNA in the peripheral blood and affected tissues and more recently by RNA localization to cutaneous capillary endothelium. However, direct localization of the viral DNA to the glomerular and cutaneous endothelium in HSP in correlation with the histopathologic findings has not been demonstrated. METHODS: Skin and kidney biopsy tissues were processed for hematoxylin and eosin, immunofluorescent, polymerase chain reaction (PCR) and reverse transcriptase in situ PCR studies. CASE PRESENTATION: A 64-year-old-female presented with palpable purpura and nephrotic range proteinuria. Kidney and skin biopsies showed IgA-associated mesangioproliferative glomerulonephritis and IgA-associated leukocytoclastic vasculitis, respectively. A diagnosis of HSP was rendered. Her clinical course was refractory to prednisone. Parvovirus B19 DNA and tumor necrosis factor alpha DNA were identified in the dermal and glomerular capillary endothelial cells and surrounding dermal inflammatory cells. CONCLUSION: This is the first documentation of B19 localization to dermal and glomerular capillary endothelium in HSP. It is important to recognize parvovirus B19-associated adult HSP cases, as the treatment of choice is intravenous gamma globulin in concert with anti-TNFalpha therapy. In contrast immunosuppressive therapy may lead to a persistent and/or worsening disease course.