In utero infection with porcine reproductive and respiratory syndrome virus modulates leukocyte subpopulations in peripheral blood and bronchoalveolar fluid of surviving piglets.

It is well known that piglets congenitally infected with porcine reproductive and respiratory syndrome virus (PRRSV) can be viremic at birth, and that preweaning mortality due to secondary infections often increases during acute outbreaks of PRRS. Therefore, an immunosuppressive effect of in utero infection has been suggested. The aim of the present study was to characterise the changes of leukocyte populations in piglets surviving in utero infection with PRRSV. A total of 27 liveborn uninfected control piglets and 22 piglets infected transplacentally with a Danish strain of PRRSV were included. At 2 and 4 weeks of age, 21 of 22 (96%) and 7 of 14 (50%) examined infected piglets were still viremic, whereas PRRSV could not be detected in the six infected piglets examined at 6 weeks of age. Flow cytometry analysis was used to determine the phenotypic composition of leukocytes in peripheral blood and bronchoalveolar lavage fluid (BALF) of 2-, 4- and 6-week-old infected piglets and age-matched uninfected controls. The key observation in the present study is that high levels of CD8(+) cells constitute a dominant feature in peripheral blood and BALF of piglets surviving in utero infection with PRRSV. In BALF, the average high level of CD8(+) cells in 2-week-old infected piglets (33.4 +/- 12.6%) was followed by a decline to 7.3 +/- 3.0 and 11.1 +/- 3.0% at 4 and 6 weeks of age. BALF of control piglets contained 1.6 +/- 0.9, 2.3 +/- 1.8 and 1.9 +/- 0.5% CD8(+) cells, only. In peripheral blood, however, the average number of CD8(+) cells remained at high levels in the infected piglets throughout the post-natal experimental period (2.8 +/- 1.9, 2.9 +/- 1.8 and 3.2 +/- 1.7 x 10(6) CD8(+) cells/ml at 2, 4 and 6 weeks, respectively). In the controls, the average levels of CD8(+) cells were 0.9+/-0.2, 1.9 +/- 1.7 and 1.6 +/- 0.5 x 10(6)/ml, respectively. Furthermore, the numbers of CD2(+) , CD4(+)CD8(+) and SLA-classII(+) cells, respectively, in peripheral blood, together with the levels of CD2(+) and CD3(+) cells in BALF were increased in the infected piglets infected in utero compared to the uninfected controls. The kinetic analyses carried out in the present study reflect that in utero infection with PRRSV modulates immune cell populations in peripheral blood and BALF of surviving piglets. The observed changes are characterised by high levels of CD8(+) cells supporting an important role of these cells in PRRSV infection. The present results, however, do not support the existence of post-natal immunosuppression following in utero infection with PRRSV.

Gastric amylin expression. Cellular identity and lack of requirement for the homeobox protein PDX-1. A study in normal and PDX-1-deficient animals with a cautionary note on antiserum evaluation.

The gene encoding amylin is implicated in the generation of amyloid in the islets of Langerhans of diabetics and is believed to be regulated by the homeodomain transcription factor PDX-1. Although gastric mucosa also produces amylin, studies on its cellular site of production have yielded highly divergent results, localizing this peptide to either gastrin, serotonin, or somatostatin cells or to combinations thereof. Using region-specific amylin antisera in combination with reverse transcriptase-polymerase chain reaction, we now document that the majority of cells expressing amylin correspond to somatostatin cells. Only a small subpopulation of gastrin cells contained immunoreactive amylin. Studies of PDX-1-deficient mice, which fail to develop gastrin cells while possessing normal numbers of somatostatin cells, revealed no detectable change in gastric amylin expression. These data show that neither normal gastrin cell development nor PDX-1 expression is needed for gastric amylin expression.

Coexpression of the gastrin and somatostatin genes in differentiating and neoplastic human cells.

Double immunofluorescence and in situ hybridizations performed on adjacent thin sections show that a population of normal antropyloric cells of the human stomach expresses both gastrin and somatostatin mRNA's and the corresponding peptides. Such cells were present in both adult and fetal antropyloric mucosa and were situated in the regenerative (isthmus) region of the antropyloric tubes. It is, hence, likely that these cells represent immature endocrine cells that yet have to be committed to either the gastrin or somatostatin lineage. Cells coexpressing gastrin and somatostatin were also detected in pancreatic endocrine tumours. The presence of gastrin-somatostatin cells during development and in tumours suggests that gastrin and somatostatin cells may differentiate from such multipotent precursor cells.

The LIM-homeodomain protein Isl-1 segregates with somatostatin but not with gastrin expression during differentiation of somatostatin/gastrin precursor cells.

The gastric epithelium is renewed from stem cells in the isthmus of the gastric glands. We describe that the two neuroendocrine peptides gastrin and somatostatin are coexpressed by isthmic stem cells. Bromodeoxyuridine labeling indicates that the coexpressing cells divide and differentiate into gastrin and somatostatin cells, which remain in paracrine contact during most of their migration down into the gland. The coexpressing cells display nuclear immunoreactivity for the transcription factors Isl-1 and CREB, which have been implicated in somatostatin gene expression. Differentiated gastrin cells lack Isl-1 reactivity and show variable staining for CREB while differentiated somatostatin cells display Isl-1 and CREB reactivity.

Characterization of MSH/ACTH-like immunoreactivity in sciatic nerves of Xenopus laevis by immunocytochemistry, western blotting and radioimmunoassay.

Previous studies have indicated that rat neurofilament protein may contain an endogenous MSH-like epitope with neuroregenerative properties. The presence of such an epitope has now been studied in nerve tissue from Xenopus laevis. Western blot analyses of sciatic nerve tissue using an assortment of sequence-specific MSH/ACTH antisera revealed the presence of two major immunoreactive protein bands of 52 and 50 kDa, which contained a mid-region MSH-like epitope. Weaker staining occurred in another protein band at 135 kDa. Immunocytochemistry revealed the immunoreactivity to reside in the axis cylinders of the nerve fibers. Other antisera, recognizing other regions of MSH/ACTH produced strong staining of Xenopus intermediate lobes, but failed to stain sciatic nerves. Thus, the proteins detected have no clear relation to either Xenopus neurofilament proteins or proopiomelanocortin.