The role of transforming growth factor-{beta} in a model of oral tolerance to the diet antigen dextrin.

In a model of immunodeficiency provoked by protein deficiency, cytosol fractions from gut IELS isolated from immunodeficient rats presenting oral tolerance to dextrin showed increased expression of TGF-beta to reduce the effect of higher levels of inflammatory cytokines.

Oral tolerance to dextrin mediated by specific suppressor T-cells induced in the intestinal intraepithelium and their systemic migration.

Antigens presented to the immune system through the oral route induce antigen specific secretory IgA and systemic unresponsiveness, termed oral tolerance (OT). We studied the induction of OT towards a diet antigen: dextrin (DEX) in rats that underwent protein deprivation and were further re-fed. Peyer's patches (PP), mesenteric lymph nodes (MLN) and spleen (Sp) cells from protein re-fed (R) rats mediated hyporesponsiveness after transfer into naïve recipient rats. Low numbers of MLN T cells transferred hyporesponsiveness while higher numbers transferred an enhancement of the delayed type hypersensitivity (DTH) reaction. MLN T cells were further separated based on their ability to bind Vicia villosa (VV). MLN VV- T cells, mainly CD8+, mediated hyporesponsiveness and MLN VV+ T cells (CD45RC+ CD4- CD8- cells) abrogated the hyporesponsiveness. Moreover, Sp DEX adherent T cells were mainly CD8+. Intestinal intraepithelial lymphocytes (iIELs) mainly CD8alpha+ gamma(delta)-TCR+ cells also inhibited the DTH response to DEX after transfer. The positive DTH response to another carbohydrate (levan) indicates the specificity of the suppression to dextrin. Therefore, our data indicate that after oral administration of DEX, two different populations of T cells were generated: one found only in the MLN that mediated DTH responses and the other one capable of migrating from the intestinal intraepithelium through PP and MLN to the Sp, mediating systemic tolerance.

Germinal center formation following immunization with the polysaccharide dextran B512 is substantially increased by cholera toxin.

We have compared the splenic responses following immunization with the T cell-independent (TI)-2 antigen native dextran B512 and with a thymus-dependent (TD) protein-dextran conjugate. Interestingly, primary immunization with native dextran induced germinal center (GC) formation in the spleen to the same extent as the protein-dextran conjugate. The GC were antigen-specific as characterized by the presence of peanut agglutinin (PNA)-positive areas that were also binding FITC-conjugated dextran. Dextran-binding B cells were also detected outside the GC as sites of antibody-producing cells. The secondary splenic response to native dextran was suppressed compared to the primary response, with almost no dextran-specific GC or extra-follicular sites with dextran-specific B cells present in the sections. This suppression could be reverted by using cholera toxin (CT) as an adjuvant for the dextran immunizations. Following native dextran immunization with CT adjuvant a secondary splenic GC response similar to a TD secondary splenic GC response was generated, with almost all the dextran-specific B cells located in the GC. Collectively, this indicates that the difference between TI and TD antigen responses is not due to different abilities in inducing GC development, rather the GC reaction is less productive for a TI antigen than for a TD antigen. CT can both increase secondary GC formation in particular for the TI form of dextran and ameliorate the GC reaction, as reflected by increased anti-dextran antibody levels.

Structural and immunochemical analysis of three alpha-limit dextrin oligosaccharides.

Complete structures are described for three urinary oligodextrins from one patient with type II and one patient with type III glycogen storage disease. GLC-MS, direct probe MS, and 1H NMR demonstrate two heptasaccharides and one hexasaccharide containing only alpha 1-4 and alpha 1-6 linkages. The observation that all three oligosaccharides were present in urine of both patients and the occurrence of alpha 1-4 and alpha 1-6 linkages in characteristic sequences indicates that the oligodextrins are limit dextrins derived from alpha-amylolytic degradation of glycogen. The binding affinities of the oligodextrins for a monoclonal antibody (401/6) raised against Glc alpha 1-6Glc alpha 1-4Glc alpha 1-4Glc, were determined by frontal analysis. The highest affinity was exhibited by Glc alpha 1-6Glc alpha 1-4Glc alpha 1-4Glc followed by the two heptasaccharides and the hexasaccharide. The results from quantitative affinity measurements agree with results of structural analysis by physical methods in that all oligodextrins containing the nonreducing terminal sequence, Glc alpha 1-6Glc alpha 1-4Glc . . . , are specifically bound by the antibody with similar affinities, but the affinity is somewhat higher for chains containing the tetrasaccharide sequence Glc alpha 1-6Glc alpha 1-4Glc alpha 1-4Glc at the nonreducing terminal. Utilization of affinity methods offers clear advantages for isolation and characterization of oligosaccharides with very similar structures.