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We have investigated interactions between human blood platelets and the vitronectin-containing fluid-phase terminal complement complex, the SC5b-9, which is a non-cytolytic variant of the membrane attack complex C%9(m). SC5b-9 affinity for the platelet membrane glycoprotein IIb/IIIa (GPIIb/IIIa) complex was demonstrated by crossed radio-immunoelectrophoresis of solubilized, washed platelets followed by incubation of the immunoplates with 125I-labelled SC5b-9 and exposure to X-ray films. Platelet adhesion to surfaces of polystyrene coated with the SC5b-9 complex was studied under static conditions in an enzyme immunoassay (EIA). Thrombin-stimulated platelets but not non-stimulated platelets adhered to the SCSb-9coated surface, and platelet adherence was inhibited in a dose-dependent manner by the tetrapeptide RGDS (Arg-Gly-Asp-Ser). This indicates an interaction between platelet GPIIb/IIIa and an RGD sequence in SC5b-9, possibly in its vitronectin moiety. The effect of the SC5b-9 complex on platelet aggregation was examined in a dual-channel aggregometer. Here the SC5b-9 complex inhibited both ADP-and thrombin-induced platelet aggregation in a dose-dependent manner. These results were confirmed by electron microscopical examination of the contents of the aggregometer cuvettes. Platelets which had been thrombin-stimulated in the presence of SC5b-9 appeared activated and had undergone secretion, but showed no aggregation. By contrast, platelets from the control experiments which had been thrombin-stimulated in the absence of SC5b-9 were aggregated. To the best of our knowledge, this is the 6rst report on a biological role of the SC5b-9 complex in platelet function.

Expression of the γ/δ T-cell receptor (TCR) on CD3⁺ intraepithelial lymphocytes (IEL) was studied in situ by two-color immunofluorescence on duodenal tissue sections from 34 infection-prone, adult patients with various types of primary hypogammaglobulinemia, classical Bruton's, Brutonlike or congenital, and common variable immunodeficiency. TCRγ/δ⁺ IEL proportions (median 4.3%, range 0.3-43.3%) were within the range (0.3-38.3%) for histologically normal controls (n = 11), and there was no significant difference between the three patient categories. The total number of CD3⁺ IEL (mostly CD8⁺) per intestinal length unit was significantly higher (P < 0.004) in patients than in controls. In addition, TCRγ/δ⁺ IEL per length unit, as well as TCRγ/δ⁺ IEL proportions, were significantly increased (P < 0.008 and P < 0.05) in 14 patients with intestinal villous atrophy. Paired staining revealed that most (≈94%) TCRγ/δ⁺ IEL in B-cell deficiency were CD8^-, and a large fraction (≈67%) expressed the Vδ1/Jδ1-encoded epitope. No relationship was found between CD3⁺ or TCRγ/δ⁺ IEL and the number of CD3⁺, CD4⁺, CD8⁺, and B lymphocytes or the CD4:CD8 ratio in peripheral blood. TCRγ/δ⁺ IEL thus appeared to maintain a normal distribution in B-cell deficiency, except for being increased in patients with villous atrophy. Enhanced T-cell-mediated immunity, as possibly reflected by the numerical increase of CD3⁺ IEL, might compensate for a deficient mucosal B-cell system. Copyright 1993, 1999 Academic Press

Background: Non-ionic, water-soluble radiographic contrast media have been suggested as intestinal permeability probes. We studied the permeability of the isosmolar contrast medium iodixanol and 51Cr-labeled ethylenediaminetetraacetic acid (EDTA) from the non-perforated colon after induction of colonic inflammation. Methods: Colonic inflammation and ulcerations were induced by luminal colonic instillation of trinitrobenzenesulfonic acid, dissolved in 40% ethanol. Controls received saline. Fourteen days later iodixanol, 320 mg I/ml, and 51Cr-EDTA were given as an enema. Urine was collected for the subsequent 6 h and subjected to high-performance liquid chromatography and gamma activity counting. Results: Urinary recovery of iodixanol and 51Cr-EDTA increased gradually with severity of the colonic inflammation. The correlation between iodixanol and 51Cr-EDTA recovery was strong (corr.coeff. = 0.97). Conclusions: Iodixanol shows as good properties as 51Cr-EDTA when used as intestinal permeability probe in the inflamed and ulcerated rat colon. Use of the radiopaque properties of-iodixanol enable intestinal probe exposure registration by film or fluoroscopy.

The aim of this study was to investigate the permeation of an isosmolar water-soluble X-ray contrast medium (CM) from the unperforated colon after experimental induction of inflammation and ulceration. One hundred and sixty-five male rats were included. In 110 rats 0.25 ml of 40% ethanol + 15 mg or 30 mg trinitrobenzene (TNB) was instilled into the colon, 7-9 cm proximal to the anus, inducing different degrees of inflammation. Fifty-five rats served as controls and had 0.25 ml saline instilled with the same procedure. At 7, 14, 21, and 28 days 3 ml of the non-ionic CM iodixanol was applied as an enema, and subsequently all urine was collected for the next 4 h. High-performance liquid chromatography analyses of the urine showed a positive relation between the severity of infiammation/ulceration in the colonic wall as assessed by a macroscopic damage score and the amount of CM excreted in the urine. Water-soluble contrast media may have prospects of combining functional tests of intestinal membrane dysfunction with segmental exposure control.

The proportion of T-cell receptor gamma/delta+ cells and the CD4/CD8 ratio relative to all CD3+ intraepithelial lymphocytes (IEL) were determined by immunofluorescence in duodenal mucosa of late-stage (mostly CDC IVC1/D) subjects (n = 21) infected with human immunodeficiency virus type 1 (HIV-1). The gamma/delta fraction (median, 14.2%; range, 1.7 to 59.8%) was increased (P < 0.03) compared with that in HIV- controls (n = 11; median 2.8%; range, 0.3 to 38%). Also, the number of gamma/delta+ IEL per mucosal unit was increased (P < 0.05) in the HIV+ subjects (median, 11.1/U) compared with the controls (3.2/U). Approximately 100% of the gamma/delta+ IEL were CD8-, and most expressed the Vdelta1vJdelta1-encoded epitope (median, 90.9%). The total number of CD3+ IEL tended to be lower than in the controls (67.4 versus 72.9/U). Both the epithelium and the lamina propria contained mainly CD8+ T cells, the median ratios of CD4+ T cells being 1 and 7.6%, respectively. This result accorded with the reduced CD4 cell number in blood (median, 18 X 10(6)/liter). The HIV+ subjects had increased serum levels of neopterin and beta2-microglobulin (both P < 0.0001), probably reflecting immunostimulation. Serum neopterin and beta2-microglobulin were inversely related to duodenal gamma/delta IEL, particularly in the premortal group (r = -0.97 and r = -0.58, respectively). The increased gamma/delta IEL might reflect enhanced intestinal protection in late-phase HIV infection. Short survival expectancy (<7 months) was associated not only with high levels of neopterin and beta2-microglobulin but also with a reduced number of duodenal gamma/delta+ cells (P < 0.03).

Celiac disease (CD) is most probably an immunological disease, precipitated in susceptible individuals by ingestion of wheat gliadin and related proteins from other cereals. The disease shows a strong human HLA association predominantly to the cis or trans encoded HLA-DQ(alpha 1*0501,beta 1*0201) (DQ2) heterodimer. T cell recognition of gliadin presented by this DQ heterodimer may thus be of immunopathogenic importance in CD. We therefore challenged small intestinal biopsies from adult CD patients on a gluten-free diet in vitro with gluten (containing both gliadin and other wheat proteins), and isolated activated CD25+ T cells. Polyclonal T cell lines and a panel of T cell clones recognizing gluten were established. They recognized the gliadin moiety of gluten, but not proteins from other cereals. Inhibition studies with anti-HLA antibodies demonstrated predominant antigen presentation by HLA-DQ molecules. The main antigen-presenting molecule was established to be the CD-associated DQ(alpha 1*0501, beta 1*0201) heterodimer. The gluten-reactive T cell clones were CD4+, CD8-, and carried diverse combinations of T cell receptor (TCR) V alpha and V beta chains. The findings suggest preferential mucosal presentation of gluten-derived peptides by HLA-DQ(alpha 1*0501, beta 1*0201) in CD, which may explain the HLA association.

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