CD44 comprises a family of type I transmembrane glycoproteins that is expressed on a wide range of cells including those of epithelial, lymphoid and myeloid lineage. Although expression of CD44 in the small intestine is typically localised in the crypts of Lieberkuhn, we have reported the expression of CD44 on mature, intestinal villus epithelial cells during the development of small bowel allograft rejection. The mechanisms underlying CD44 up-regulation are unknown, although it may be influenced by localised cytokine production. This study used flow cytometry to assess the effects of recombinant IFN-gamma and TNF-alpha on CD44 expression and hyaluronan binding by the rat small intestinal epithelial cell lines, RIE and IEC 6. IFN-gamma upregulated CD44 expression on RIE (155% of unstimulated control) and IEC 6 (209% of unstimulated control) cells, whereas TNF-alpha had no effect. IFN-gamma had no qualitative effect on CD44, as binding of the ubiquitously expressed extracellular matrix polysaccharide hyaluronan was unchanged. RIE and IEC 6 cells expressed the 82 kDa and 130 kDa major isoforms of CD44, however cytokine stimulation did not affect the expression of these, nor did stimulation induce the expression of other variants. In summary, these findings demonstrate that CD44 expression by intestinal epithelial cells can be regulated by cytokines, yet their ability to bind hyaluronan and the isoform of the expressed CD44 remains unaltered. It appears that localised inflammatory conditions and cytokine production may modify epithelial cell expression of CD44, however the physiological role for such a response has yet to be elucidated.
Objectives: This paper describes the components of the Caribbean Institute on Alcoholism and Other Drug Problems (CARIAD), a long-standing substance abuse training programme. It seeks to explain how certain strategies and pedagogic techniques may be contributing to its success. Methods: Authors deconstruct the core elements of CARIAD to demonstrate how the programme effectively meets the characteristics of a community of practice. The processes used to develop the learning community and the specific pedagogic strategies and techniques that foster collaborative knowledge construction and sharing are described. Results: Caribbean Institute on Alcoholism and Other Drug Problems brings together a multidisciplinary, multinational group of individuals with interest in substance abuse. The programme provides a range of formal and informal learning activities which focus on sharing best practices and creating new sociocultural relevant knowledge to advance the domain of professional practice in substance abuse. The components of CARIAD promote interactivity, rapid bonding and a sense of identity. Caribbean Institute on Alcoholism and Other Drug Problems provides a unique platform for cultural sharing that gives participants an opportunity to reveal insights into local and regional expressions of substance abuse challenges. Participants, however, recognize the absence of structured continuity and the diminution of what could be accomplished by graduates over time. Conclusion: The success of CARIAD as a regional learning platform may be related to its success as a Caribbean community of practice for substance abuse. Caribbean Institute on Alcoholism and Other Drug Problems would do well to sustain the community of practice, generating and maintaining ongoing participation and collaboration among graduates. This can potentially serve to create new strategies for advancing the region in the area of substance abuse.
Soluble MHC class I antigens can be detected in the serum of humans and various animals and appear in the circulation shortly after liver transplantation. The precise role of these antigens is currently uncertain, but soluble MHC class I may be involved in immunomodulation. We have developed an enzyme linked immunosorbent assay for soluble rat MHC class I (RT1a) molecules and monitored the kinetics of antigen release following in vitro stimulation of splenic mononuclear cells. A 4 day DA splenocyte Con A supernatant provided a source of soluble class I antigens and was arbitrarily assigned a concentration of 1000 units/ml. Ninety six well plates were coated with a rat RT1a-specific mAb (MN4-91-6) and soluble class I binding was detected using a biotinylated mAb reactive with a monomorphic region of the rat MHC class I molecule (OX18) followed by a streptavidin-alkaline phosphatase conjugate and substrate. The intra- and interassay variations were typically less than 5% and 10% respectively, to give a working range for the assay of between 62.5 and 1000 units/ml. Mitogenic stimulation led to a progressive increase in soluble class I levels in culture supernatants. This assay will be valuable in differentiating recipient and graft responses following experimental organ transplantation.
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