Characterization and epitope mapping of two monoclonal antibodies against human CD99

CD99 plays an critical role in the diapedesis of monocytes, T cell differentiation, and the transport of MHC molecules. Engagement of CD99 by agonistic monoclonal antibodies has been reported to trigger multifactorial events including T cell activation as well as cell-cell adhesion during hematopoietic cell differentiation. In this study, to identify the functional domains participating in the cellular events, we mapped the epitopes of CD99, which are recognized by two agonistic CD99 monoclonal antibodies, DN16 and YG32. Using recombinant fusion proteins of GST with whole or parts of CD99, we found that both antibodies interact with CD99 molecules independently of sugar moieties. DN16 mAb detected a linear epitope located in the amino terminal region of CD99 while YG32 mAb bound another linear epitope in the center of the extracellular domain. To confirm that the identified epitopes of CD99 are actually recognized by the two mAbs, we showed the presence of physical interaction between the mAbs and the fusion proteins or synthetic peptides containing the corresponding epitopes using surface plasmon resonance analyses. The dissociation constants of DN16 and YG32 mAbs for the antigen were calculated as 1.27 X 10(-7) and 7.08 X 10(-9) M, respectively. These studies will help understand the functional domains and the subsequent signaling mechanism of CD99.

Effects of intragastric pH increment by omeprazole on the eradication rate of Helicobacter pylori / 대한내과학회지

BACKGROUND: Although proton pump inhibitors (PPIs) combined with antibiotics have been known to increase the antimicrobial activity, the effect of PPIs on the eradication of Helicobacter pylori (H. pylori) is controversial. The aims of the present study were to evaluate the effect of omeprazole on the amoxicillin activity for the eradication of H. pylori using prospective double-blind clinical trial and to assess the inhibitory activity of amoxicillin on the H. pylori according to the pH in vitro. METHODS: Thirty healthy volunteers with endoscopically proven H. pylori infection were randomized to either OA group (n=14); 2 weeks omeprazole (20 mg, b.i.d.) plus amoxicillin (750 mg, b.i.d.) or PA group (n=16); 2 weeks placebo plus the same antibiotic. The H. pylori status was assessed at baseline and at 6-week after the initiation of treatment, and the eradication rate of H. pylori was compared between two groups. Intragastirc pH and serum gastrin level were measured before and 1-week after the treatment also. In vitro, minimal inhibitory concentrations (MICs) of amoxicillin were assessed at the different pHs of media. RESULTS: Intragastric pH significantly increased in OA group (p=0.02), however, did not change in PA group. The changes of intragastric pH parameters after 1-week treatment were significantly different between two groups (p50%) in the eradication rate of H. pylori.

A Case of Primary CD56+ T/NK Cell Lymphoma of the Colon / 대한소화기내시경학회지

Primary T/natural killer (NK) cell lymphoma of the colon is extremely rare. Although this tumor is well known to arise in the nasal cavity and upper aerodigestive tract, only a few cases have been reported in the colon as an extranodal disease, which were mainly reported in East Asia. Recently, several authors have described the clinicopathologic, immunophenotypic, and genotypic features of CD56-positive tumor as a distinct subgroup due to its aggressive clinical behavior and poor prognosis. However, primary T/NK cell lymphoma of the colon may present a difficult diagnostic challenge to physicians because the symptoms and colonoscopic findings are non-specific and available data in the literature are very limited. We herein describe a case of primary T/NK cell lymphoma of the colon presenting as ulcerative lesions similar to Crohn's colitis and complicated by cecal bleeding/perforation.

Features of Malignant Biliary Obstruction Affecting the Patency of Metallic Stents: A Multicenter Study / 대한소화기내시경학회지

BACKGROUND/AIMS: Although metalic stents are established therapeutic options for the palliation of malignant biliary obstruction, it remains unclear which stricture or stent related factors affect the stent patency. METHODS: Metallic Wallstents (Microvasive, Boston-Scientific, MA, U.S.A.) were inserted endoscopically in 68 patients (mean age; 70.2+/-8.5, M:F=38:30) with malignant biliary obstruction. Patency rates were prospectively analyzed according to the characteristics of malignant strictures including length, morphologic type and degree of stricture. Furthermore, patient age, initial serum bilirubin level, the length of stent, the adequate expansion time, and the location of the distal stent end were evaluated as possible factors affecting the stent patency. Stent patency was assessed using the survival analysis of the Kaplan-Meier estimation and Cox regression analysis. RESULTS: Median overall stent patency was 231 days and overall rate of stent occlusion was 41.2% (28/68). The causes of stent blockage were tumoral ingrowth in 23 patients (33.8%), distal overgrowth of the cancer in 3 (4.4%), proximal overgrowth in 1 (1.5%) and sludge incrustation in 1 patient (1.5%). No significant differences in metallic stent patency rates according to primary tumor type, length and morphologic type of stricture, and length and location of distal end of the stent were found. Log-rank test and multivariate regression analysis, however, demonstrated that the degree of stricture assessed by cannula or guidewire passage and the adequate expansion time of the stent are independent factors associated with long-term metallic stent patency. CONCLUSIONS: Our study showed that early expansibility of the stent and easy passage of larger-caliber instruments over the stricture were favorable factors for long-term patency of the metallic stent.