CD103+CD11b+ dendritic cells (DCs) are unique to the intestine, but the factors governing their differentiation are unclear. Here we show that transforming growth factor receptor 1 (TGFβR1) has an indispensable, cell intrinsic role in the development of these cells. Deletion of Tgfbr1 results in markedly fewer intestinal CD103+CD11b+ DCs and a reciprocal increase in the CD103−CD11b+ dendritic cell subset. Transcriptional profiling identifies markers that define the CD103+CD11b+ DC lineage, including CD101, TREM1 and Siglec-F, and shows that the absence of CD103+CD11b+ DCs in CD11c-Cre.Tgfbr1 fl/fl mice reflects defective differentiation from CD103−CD11b+ intermediaries, rather than an isolated loss of CD103 expression. The defect in CD103+CD11b+ DCs is accompanied by reduced generation of antigen-specific, inducible FoxP3+ regulatory T cells in vitro and in vivo, and by reduced numbers of endogenous Th17 cells in the intestinal mucosa. Thus, TGFβR1-mediated signalling may explain the tissue-specific development of these unique DCs.

Porcine reproductive and respiratory virus (PRRSV) primarily infects and destroys alveolar macrophages of the pig. The aim of the present study was to characterize the changes of leukocyte populations in the broncho-alveolar lavage fluid (BALF) of PRRSV-infected pigs. Piglets were inoculated intranasally with PRRSV strain LV ter Huurne. On various days post-infection the piglets were sacrificed and the lungs removed, washed semi-quantitatively and analysed by flow cytometry. The total number of recovered BALF cells increased approximately 10 times between day 10 and day 21 of infection and decreased thereafter. The number of small low-autofluorescent cells (SLAC), i.e. lymphocytic and monocytic cells, increased very strongly from day 2 until day 21 of infection; in contrast, the number of large highly autofluorescent cells (LHAC), i.e. mostly macrophages, remained constant until day 14 of infection, increased slightly on day 21 and then decreased. On day 21 of infection in specific-pathogen-free piglets approximately 60% of the SLAC consisted of CD2(+)CD8(+)CD4(-)gammadeltaTCR(-) cells, which were partly CD8(+)CD6(+) and partly CD8(+)CD6(-). These phenotypes correspond to that of cytotoxic T-cells and natural killer cells respectively. From these results we can conclude that during a PRRSV infection the total number of BALF cells increases mainly due to an influx of lymphocytic cells with a cytolytic phenotype.

A child, L.B., born at term, the third child whose older sister has juvenile idiopathic arthritis successfully treated with azathioprine, presented at 3 months with 6 to 8 bloody diarrheal stools per day, resolving spontaneously within 1 week. She was breast-fed for 4 months, when solid food was started. Formula was introduced at 6 months. She was asymptomatic between 4 and 10 months, but then presented again with bloody diarrhea, up to 10 stools per day, with mucus and bright red blood in her diapers. Upper endoscopy and histology were normal. Lower endoscopy showed pancolitis with loss of colonic haustrations, friability, absent vascular pattern, and some small ulcerations ( Fig. 1). Histology was consistent with an ulcerative colitis (UC)-like phenotype; additionally, perinuclear anti-neutrophil cytoplasmic antibody was positive (1/160). Oral (50-60 mg Á kg À1 Á day À1 ) and rectal (333 mg/day) mesalamine was initiated. Following a good initial response, she relapsed 2 months later. At 13 months, azathioprine (2.0 mg Á kg À1 Á day À1 ) and prednisolone (2 mg Á kg À1 Á day À1 ) were initiated. Although she responded with decreased severity of symptom, stools remained frequent, bloody, and liquid. General condition, weight, and linear growth remained acceptable. The use of an amino acid-based formula for several months had no effect. Iron supplements failed to compensate for the rectal bleeding, and transfusion of packed red blood cells was needed every 3 to 4 weeks. Several probiotics, including VSL-3, proved unsuccessful. Infliximab treatment (5 mg/kg at 0-2-6-10 weeks) had no effect. An adverse reaction to sirolimus (Rapamune; Pfizer Pharmaceutical, New York, NY) made further administration impossible. Intravenous broad-spectrum antibiotics and total parental nutrition were administered for severe flares. Repeat biopsies with histology including electron microscopy did not reveal etiologies other than the ''UC-like image.'' Antigen detection for Clostridium difficile was negative. An immunodeficiency was suspected because of L.B.'s young age at onset. Lymphocyte numbers and subsets were normal. Immunoglobulin levels were within the normal range for age. B-cell subsets for common variable immunodeficiency were analyzed and showed no decrease in switched memory B cells. Vaccination response against tetanus was adequate. Normal

The aim of this study was to investigate the effects of a porcine reproductive and respiratory syndrome virus (PRRSV) infection on the development of the immune response after pseudorabies virus (PRV) vaccination in pigs. Pigs were intranasally inoculated with the European PRRSV strain, Lelystad virus ter Huurne, and were vaccinated intramuscularly with PRV 2 weeks later (LV-PRV group). Control pigs were vaccinated with PRV only (PRV group). Eight weeks after PRV vaccination, pigs from both groups were challenged intranasally with wild-type PRV. We measured the lymphoproliferative, and the cytolytic responses to PRV of peripheral blood mononuclear cells (PBMC), isolated from blood samples. In addition, serum samples were examined for antibodies against PRV and LV. One week after PRV vaccination, PBMC proliferated abundantly to PRV in both groups. However, in the LV-PRV group the lymphoproliferative response declined after 1 week, whereas, in the PRV group, the lymphoproliferative response was high for 3 weeks and declined thereafter (P<0.05). After challenge, the lymphoproliferative response was 1 week earlier and was consistently and significantly higher in the PRV group than in the LV-PRV group. The PRV-specific killing was higher at 3 weeks after PRV vaccination and 5 weeks after PRV challenge 19+/-3 and 24+/-6%, respectively, in the PRV group, compared to 7+/-4 and 6+/-9%, respectively, in the LV-PRV group (P<0.05). However, later after vaccination and challenge the cytolytic response was identical in both groups. The antibody titre against PRV developed equally in both groups. After challenge, no PRV virus was isolated from both groups. From these results we conclude that, although PRRSV infection did cause changes in the time course of the T-lymphocyte response after PRV vaccination, PRRSV infection did not inhibit the development of vaccine-induced protection after PRV.

We previously observed that pseudorabies virus (PRV)-induced, cell-mediated cytolysis in pigs includes killing by natural killer (NK) cells. We also observed that IL-2 stimulation in vitro of naive PBMC expands porcine NK cells. The purpose of this study was to compare the phenotypes of the cytolytic subsets stimulated in vitro by PRV and by IL-2. PBMC were isolated from blood of PRVimmune and naive pigs and stimulated in vitro with PRV or IL-2. After 6 days, the frequency of various lymphocyte subsets in these cultured PBMC was determined by flow cytometry : the cells were separated with a magnet-activated cell sorter and the cytolytic activity of the separated populations was determined. When lymphocytes were separated and analysed with FACScan, the following lymphocyte subsets were discriminated : CD6 M These results demonstrate that both natural killing and killing by classical PRV-specific CTL were detected in PRV-immune pigs, whereas IL-2 stimulation of PBMC isolated from naive pigs mainly induced natural killing.