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Inflammatory destruction of insulin-producing ␤ cells in the pancreatic islets is the hallmark of insulin-dependent diabetes mellitus, a spontaneous autoimmune disease of non-obese diabetic mice resembling human juvenile (type I) diabetes. Histochemical analysis of diabetic pancreata revealed that mononuclear cells infiltrating the islets and causing autoimmune insulitis, as well as local islet cells, express the CD44 receptor; hyaluronic acid, the principal ligand of CD44, is detected in the islet periphery and islet endothelium. Injection of anti-CD44 mAb 1 hr before cell transfer of diabetogenic splenocytes and subsequently on alternate days for 4 weeks induced considerable resistance to diabetes in recipient mice, reflected by reduced insulitis. Contact sensitivity to oxazolone was not influenced by this treatment. A similar antidiabetic effect was observed even when the anti-CD44 mAb administration was initiated at the time of disease onset: i.e., 4 -7 weeks after cell transfer. Administration of the enzyme hyaluronidase also induced appreciable resistance to insulin-dependent diabetes mellitus, suggesting that the CD44 -hyaluronic acid interaction is involved in the development of the disease. These findings demonstrate that CD44-positive inflammatory cells may be a potential therapeutic target in insulin-dependent diabetes.T he inflammatory cascade in affected organs of autoimmune diseases is a complex process that involves triggering of the immunological response, release of chemokines, cytokines, and toxic agents (e.g., reactive oxygen) by the activated cells, stimulation of endothelial cells, up-regulation of cell surface adhesion molecules, transendothelial cell migration, and a shift in the Th1͞Th2 balance in favor of the Th1 cells (1). Hence, the destructive autoimmune inflammatory process depends substantially (but not exclusively) on cell migration and cell interaction with matrix components of target organs. The destruction of pancreatic islet ␤-cells in insulin-dependent diabetes mellitus (IDDM) by invading leukocytes and the consequent deterioration of the insulin-dependent glucose homeostasis is an excellent example of such an autoimmune process (2, 3), although neither the nature of the triggering self-antigen nor the molecules associated with its recognition and presentation have been unequivocally identified.Whereas the function of selectins and integrins in supporting inflammatory cell migration and lodgment has been well established (4), the role of cell surface CD44 has only recently attracted attention (5). Alternative splicing and͞or posttranslation modifications generate many CD44 isoforms. The large array of CD44 isoforms is mainly attributable to the insertion of amino acid sequences, encoded by different combinations of 10 variant exons, into a membrane proximal position of the extracellular domain. Transcripts in which these variant exons are spliced out encode the most common and widely expressed 85-kDa isoform, known as standard CD44. The expression of CD44 isoforms containing s...

SUMMARYThe apparent intensity of hyaluronan (HA) staining in tissue sections can vary as a function of fixation techniques. We examined the histochemical distribution of HA in normal human skin using an HA-specific binding peptide derived from bovine nasal cartilage. The HA, particularly in the dermis, was best preserved in sections fixed in 10% acidformalin with 70% ethanol. In contrast, sections fixed in the routine 10% neutral-buffered formalin had a much weaker intensity of HA staining. Furthermore, acid-formalin/ethanolfixed sections retained much of their apparent HA after incubation with saline, in contrast to the neutral formalin-fixed sections, in which most of the stainable HA was lost. Such marked differences in staining intensity were not observed in slides stained with Alcian blue, a procedure pressumed to stain HA as well as other glycosaminoglycans. Staining using the HA binding peptide was entirely absent when sections were first preincubated in hyaluronidase, whereas similar Alcian blue-stained sections retained most of their staining intensity. Caution should be exercised in evaluating the distribution of HA in tissues using the HA binding peptide, particularly when different fixation techniques among several laboratories are being compared. In addition, the ability to evaluate the HA content of tissues using Alcian blue staining should be reconsidered. The sulfated glycosaminolglycans of the "ground substance" appear to be the predominant substrates for Alcian blue.