Phenotypic Characterization of Peripheral T Cells and Their Dynamics in Scrub Typhus Patients

Background: scrub typhus,caused by orientia tsutsugamushi infection,is one of the main causes of febrile illness in the asia-pacific region. although cell-mediated immunity plays an important role in protection,little is known about the phenotypic changes and dynamics of leukocytes in scrub typhus patients. methodology/principal findings: to reveal the underlying mechanisms of immunological pathogenesis,we extensively analyzed peripheral blood leukocytes,especially t cells,during acute and convalescent phases of infection in human patients and compared with healthy volunteers. we observed neutrophilia and cd4+ t lymphopenia in the acute phase of infection,followed by proliferation of cd8+ t cells during the convalescent phase. massive t cell apoptosis was detected in the acute phase and preferential increase of cd8+ t cells with activated phenotypes was observed in both acute and convalescent phases,which might be associated or correlated with elevated serum il-7 and il-15. interestingly,peripheral treg cells were significantly down-regulated throughout the disease course. conclusions/significance: the remarkable decrease of cd4+ t cells,including treg cells,during the acute phase of infection may contribute to the loss of immunological memory that are often observed in vaccine studies and recurrent human infection. © 2012 cho et al.