CD43-independent augmentation of mouse T-cell function by glycoprotein cleaving enzymes

Previous work has shown that the function of mouse CD4 + T cells can be augmented by an enzyme, O -sialoglycoprotein endopeptidase (OSGE), which cleaves surface CD43, suggesting the idea that the high levels of glycosylated CD43 found on T cells from aged mice may contribute to immune senescence. New results now show that OSGE improves T-cell function even in mice lacking CD43, showing that other glycoproteins must contribute to the OSGE effect on function. Evaluation of other enzymes found two whose ability to stimulate CD4 activation was higher in aged than in young T cells. One of these, PNGase F, is a glycosidase specific for N-linked glycans, and the other, ST-Siase(2,3) from Salmonella typhimurium , is specific for α2,3-linked terminal sialic acid residues. Parallel lectin-binding experiments showed that removal of α2,3-linked sialic acid residues vulnerable to PNGase F and ST-Siase(2,3) was also greater in old than in young T cells. The preferential ability of PNGase F and ST-Siase(2,3) to improve the function of T cells from aged mice may involve cleavage of glycoproteins containing α2,3-linked sialic acid residues on N-linked or O-linked glycans or both.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75621/1/j.1365-2567.2006.02419.x.pd

Sexual Transmission of a Plant Pathogenic Bacterium, Candidatus Liberibacter asiaticus, between Conspecific Insect Vectors during Mating

Candidatus Liberibacter asiaticus is a fastidious, phloem-inhabiting, gram-negative bacterium transmitted by Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). The bacterium is the presumed causal agent of huanglongbing (HLB), one of the most destructive and economically important diseases of citrus. We investigated whether Las is transmitted between infected and uninfected D. citri adults during courtship. Our results indicate that Las was sexually transmitted from Las-infected male D. citri to uninfected females at a low rate (<4%) during mating. Sexual transmission was not observed following mating of infected females and uninfected males or among adult pairs of the same sex. Las was detected in genitalia of both sexes and also in eggs of infected females. A latent period of 7 days or more was required to detect the bacterium in recipient females. Rod shaped as well as spherical structures resembling Las were observed in ovaries of Las-infected females with transmission electron microscopy, but were absent in ovaries from uninfected D. citri females. The size of the rod shaped structures varied from 0.39 to 0.67 µm in length and 0.19 to 0.39 µm in width. The spherical structures measured from 0.61 to 0.80 µm in diameter. This investigation provides convincing evidence that a plant pathogenic bacterium is sexually transmitted from male to female insects during courtship and established evidence that bacteria persist in reproductive organs. Moreover, these findings provide an alternative sexually horizontal mechanism for the spread of Las within populations of D. citri, even in the absence of infected host trees

Profile of Central and Effector Memory T Cells in the Progression of Chronic Human Chagas Disease

Chagas disease is a parasitic infection caused by protozoan Trypanosoma cruzi that affects approximately 11 million people in Latin America. The involvement of the host's immune response on the development of severe forms of Chagas disease has not been fully elucidated. Studies on the immune response against T. cruzi infection show that the immunoregulatory mechanisms are necessary to prevent the deleterious effect of excessive immune response stimulation and consequently the fatal outcome of the disease. A recall response against parasite antigens observed in in vitro peripheral blood cell culture clearly demonstrates that memory response is generated during infection. Memory T cells are heterogeneous and differ in both the ability to migrate and exert their effector function. This heterogeneity is reflected in the definition of central (TCM) and effector memory (TEM) T cells. Our results suggest that a balance between regulatory and effectors T cells may be important for the progression and development of the disease. Furthermore, the high percentage of central memory CD4+ T cells in indeterminate patients after stimulation suggests that these cells may modulate host's inflammatory response by controlling cell migration to tissues and their effector role during chronic phase of the disease

Mechanisms of T cell organotropism

F.M.M.-B. is supported by the British Heart Foundation, the Medical Research Council of the UK and the Gates Foundation

Flow visualization and supersonic combustion studies of an acoustically open strut cavity

In this study, the supersonic flow over strut cavities was experimentally studied to understand flow features. Instantaneous schlieren imaging in non-reacting flow experiments exhibited the seven types of waves associated with cavity pressure oscillations and the formation of unstable shear layers on both sides. The shear layers moved in and out in synchronous and asynchronous modes at the trailing edge of the strut cavities. The symmetrical wave structure appeared on both sides in the synchronous mode, whereas the shear layers appeared in different stages of the cavity pressure oscillation cycle in the asynchronous mode, resulting in an asymmetrical wave structure. The pressure waves generated at the trailing edge of the strut cavities perturbed the shear layers during their movement toward the leading edge, creating a wavy shear layer with alternate troughs and crests. The pressure oscillations of the strut cavities had high-amplitude cavity modes with broadband noises, and their amplitude decreased from the trailing edge to the leading edge. The estimated recovery factor using the time lag between the signals of the leading and trailing edges showed that the flow inside the strut cavities was low subsonic. The measured dominant pressure oscillation modes had a closer match with the Rossiter modes. The pressure coefficient demonstrated that fluid accumulation inside the cavity increased with an increase in the aspect ratio. Furthermore, a higher fluid mass accumulated at the trailing edge than at the leading edge, and the difference in fluid accumulation increased with an increase in the aspect ratio. Supersonic combustion experiments with strut cavities showed that the strut cavity stabilized the flame. Moreover, the addition of an acoustically open strut cavity ahead of the flame-stabilizing cavity advanced the heat release location upstream