SUMMARYDespite the central role that dendritic cells (DC) play in immune regulation and antigen presentation, little is known about porcine DC. In this study, two sources of DC were employed. Bone marrow haematopoietic cell-derived DC (BM-DC) were generated using granulocyte± macrophage colony-stimulating factor (GM-CSF) in the presence or absence of tumour necrosis factor-a (TNF-a). Monocyte-derived DC (Mo-DC) were generated with GM-CSF and interleukin-4 (IL-4). In both systems, non-adherent cells developed with dendritic morphology, expressing high levels of major histocompatibility complex (MHC) class II. The presence of TNF-a increased the BM-DC yield, and enhanced T-cell stimulatory capacity. Both BM-DC and Mo-DC expressed the pan-myeloid marker SWC3, as well as CD1 and CD80/86, but were also CD14 + and CD16 + . The CD16 molecule was functional, acting as a low-af®nity Fc receptor. In contrast, the CD14 on DC appeared to differ functionally from monocyte CD14: attempts to block CD14, in terms of lipopolysaccharide (LPS)-induced procoagulant activity (PCA), failed. The use of TNF-a or LPS for DC maturation induced up-regulation of MHC class II and/or CD80/86, but also CD14. Allogeneic mixed leucocyte reactions and staphylococcal enterotoxin B antigen presentation assays demonstrated that these DC possessed potent T-cell stimulatory capacity. No T helper cell polarization was noted. Both the BM-DC and the Mo-DC induced a strong interferon-c and IL-4 response. Taken together, porcine DC generated in vitro possess certain characteristics relating them to DC from other species including humans, but the continued presence of CD14 and CD16 on mature and immature porcine DC was a notable difference.

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SUMMARYThe kinetics of monocyte-macrophage differentiation was analysed using two Swine Workshop Cluster (SWC ) CD molecules: SWC1 and SWC9. Myeloid cells were selected by labelling for the common myeloid antigen, SWC3. Confirmation of macrophage identification used acid phosphatase and phagocytosis activities. During differentiation, SWC1 was gradually lost. SWC9 was absent on monocytes but up-regulated early. Consequently, monocytes were SWC1+ SWC9− and macrophages were SWC1− SWC9+. An additional, intermediate, cell population was identified as SWC1+ SWC9+. Size and granularity characteristics mirrored the monocyte, macrophage and intermediate-cell phenotypes. Overall, SWC9 up-regulation was central in macrophage differentiation and dependent on plasma factors. The concomitant loss of SWC1 was independent of these factors, but always associated with mature macrophages. Upon up-regulation of SWC9, the SWC1+ SWC9+ intermediate monocytic cells became susceptible to African swine fever virus infection. These results demonstrate the heterogeneity of monocytic cell differentiation and the importance of these characteristics for interaction with monocytotropic viruses.

A milk immunoglobulin concentrate (MIC) containing antibodies to enteropathogenic E. coli strains was prepared by hyperimmunisation of pregnant cows and using the milk obtained during the first 6 to 8 days of lactation. The sterile concentrate contained 70 to 80% protein and 35 to 40% immunoglobulin. The antibacterial activity was measured by bacterial passive agglutination, bacteriostatic activity in vitro, phagocytic clearance in vivo, and a protection test in mice. Though differences in titers were observed, adequate immunologic activity was demonstrated by these tests. Clinical studies were performed with 60 patients (aged 10 days to 18 months) suffering from diarrhoea with isolation of enteropathogenic E. coli. They were treated for 10 days with MIC and stool cultures were done prior to, during, and 2, 3 and 4 days after termination of treatment. Among 51 patients infected with E. coli strains incorporated in the vaccine, stool cultures became negative in 43 (84.3%) after treatment with MIC and 8 remained positive. Nine patients infected with strains O 78:K80(B-) and O 114:K--(B-)--which were not included in the vaccine used for immunisation--served as controls. Only one patient in this group became negative. If all patients receiving antibiotics for non intestinal infections during the treatment period are omitted the results remained unaltered: MIC was effective in 32 out of 38 patients (84.2%). These differences were highly significant. These results provide evidence that treatment with specific MIC is effective in eliminating enteropathogenic E. coli from the intestine.

Double-stranded secondary structures on mRNA delivered by lipofection can activate MoDCs. This could have important implications for mRNA-based immunomodulation of DCs, DC-based immunotherapy, and formulation of RNA-based vaccines. In addition, this report describes the first in vitro steps towards development of a novel large animal model system to evaluate DC-based vaccines against infectious diseases.