ABSTRACT
The integrin CD11b/CD18 promotes leukocyte extravasation during inflammation. Filamentous hemagglutinin (FHA) of Bordetella pertussis binds to CD11b/CD18, raising the possibility that peptides derived from FHA might inhibit leukocyte migration. The Arg-Gly-Asp (RGD) sequence of FHA has been suggested to modulate binding of ligands to CD11b/CD18. Peptides derived from this region inhibited adherence and transendothelial migration of neutrophils in vitro and prevented recruitment of leukocytes into the cerebrospinal fluid in an experimental model of meningitis in rabbits. The mechanism of the antiinflammatory effect may involve modulation of the activity of CD11b/CD18 through peptide interaction with the leukocyte response integrin/integrin-associated protein complex.
Subject(s)
Adhesins, Bacterial/pharmacology , CD18 Antigens/physiology , Cell Adhesion Molecules/biosynthesis , Chemotaxis, Leukocyte/drug effects , Hemagglutinins/pharmacology , Macrophage-1 Antigen/physiology , Neutrophils/physiology , Peptide Fragments/pharmacology , Virulence Factors, Bordetella , Amino Acid Sequence , Animals , Bordetella pertussis/immunology , Cells, Cultured , Dose-Response Relationship, Drug , Endothelium, Vascular , Humans , L-Selectin , Meningitis/blood , Meningitis/cerebrospinal fluid , Meningitis/immunology , Molecular Sequence Data , Neutrophils/drug effects , Oligopeptides , Rabbits , Respiratory Burst , Umbilical VeinsABSTRACT
Type I, insulin-dependent diabetes (IDD) in both man and animals results from a specific autoimmune destruction of the pancreatic beta cells involving both humoral and cellular immune mechanisms. The pathognomonic histologic lesion, termed insulitis, is an inflammatory and immune cell infiltrate of the pancreatic islet cells. While recent histological and flow cytometric analyses have identified the cell composition of the infiltrate, the presence of a cell population may not reflect the functional reactivities important for beta cell destruction. In the present study, we have investigated the possible functional reactivities of islet-infiltrating mononuclear cell populations by measuring increased cytokine mRNA usage. Results indicate that 1) cytokine mRNA profiles exhibited by islet-infiltrating cells of female and male NOD mice were quite similar with the exception of IL-6 expression and the marked differences in the levels of IL-2 receptor and IL-1 alpha mRNA, 2) CD4+ T lymphocytes expressed IL-4, presumably IL-5, and occasionally IL-10 mRNA but no detectable IL-2 mRNA, 3) CD8+ T lymphocytes exhibited TNF-beta, perforin and high levels of IFN-gamma, and 4) IL-7 was expressed in the islet at very high levels. These findings, together with our earlier flow cytometric analyses of the islet-infiltrating cells, have permitted construction of a detailed model for the natural history of autoimmune diabetes. Interestingly, this model, based on a TH2- and not a TH1-mediated scheme, questions the more popular concepts currently thought to form the bases of the autoimmune reactions underlying IDD.
Subject(s)
Diabetes Mellitus, Type 1/immunology , Islets of Langerhans/pathology , T-Lymphocytes, Helper-Inducer/physiology , Animals , Base Sequence , CD4-Positive T-Lymphocytes/metabolism , Cytokines/genetics , Diabetes Mellitus, Type 1/metabolism , Diabetes Mellitus, Type 1/pathology , Disease Models, Animal , Female , Islets of Langerhans/immunology , Male , Mice , Mice, Inbred C3H , Mice, Inbred CBA , Mice, Inbred NOD , Molecular Sequence Data , RNA, Messenger/analysisABSTRACT
Type I, insulin-dependent diabetes (IDD) in man and the NOD (non-obese diabetic) mouse is believed to result from an autoimmune destruction of pancreatic beta (beta) cells. In both species the pathologic correlate of this destruction is a peri- and intra-islet immune cell infiltrate, referred to as insulitis, easily recognized histologically. Although histologic studies of insulitis have established the autoimmune nature of IDD, controversy remains concerning the phenotypes and especially function of the islet-infiltrating immune cells. In the present study, we reveal a new protocol which permits enumeration of islet-infiltrating leukocytes using flow cytometry (FACS). Using this technique, we have analyzed systematically the changes in major leukocyte phenotypes during the development of the insulitis lesion. Results indicate that: 1) the first islet-infiltrating leukocytes are class II+, Ig- monocytes and CD8+ T lymphocytes, 2) after a slight decrease in the CD8+ cell population, an influx of CD4+ T lymphocytes occurs, accompanied by increasing numbers of CD8+ T cells, as well as IgM+ and IgG+ B lymphocytes, 3) whereas all the IgM+ B cells appear to be CD5+, between 70-95% of IgG+ B cells express CD5, and 4) throughout the response, the class II+, IgG-cell population remains relatively constant. These data, together with our previous work showing that autoantibody binds to pancreatic beta cells prior to leukocytic infiltration, permit construction of a working model for the natural history of insulitis in the NOD mouse. Briefly, the initial cellular response against the beta cell, which begins between 5-7 weeks of life, appears to be a local inflammation in which class II-positive macrophages and CD8-positive cells (possibly with antibody-dependent cell-mediated cytotoxic potential) infiltrate the islet. Finally, T helper cells are activated, traffic briefly through the islet, and elicit a B lymphocyte and T killer cell invasion of the islet that ultimately leads to beta cell necrosis.
