Inhibition of lymphocyte proliferative responses to Helicobacter pylori by plastic adherent cells.

A study was carried out on 49 H. pylori-positive and 11 H. pylori-negative patients to determine the reactivity of peripheral blood lymphocytes (PBL) to phytohemagglutinin (PHA) and acid glycine extract (AGE) of H. pylori, and to identify cells responsible for imunosuppression. Based on response to PHA stimulation, cell-mediated immunity of all patients were competent. In some patients, however, response to AGE of H. pylori was suppressed by plastic adherent cells. This study provided evidence of the presence of plastic adherent suppressor cells which suppressed PBL response to AGE of H. pylori but not to PHA suggesting that immunosuppression is antigen specific. There is also an indication that immunosuppression may be species-specific as PBL devoid of plastic adherent cells only responded to stimulation by AGE of H. pylori but not that to AGE of C. jejuni.

Enzyme biotypes of Helicobacter pylori isolated from Penang, Peninsular Malaysia.

A total of 52 clinical strains of Helicobacter pylori were characterized on the basis of preformed enzyme production with API ZYM kits. Using the biotyping schemes as defined by Reina and Alomar (1989), Kung et al (1989) and Matsumoto et al (1996), 15.3% (8/52), 13.5% (7/52) and 11.5% (6/52) of the isolates were not biotypable, respectively. Two enzymes, valine arylamidase and cystine arylamidase could be additionally used to differentiate between isolates. Our isolates were either negative or positive for both the enzymes or positive only for cystine arylamidase. We propose the incorporation of these two enzymes into the Matsumoto et al (1996) biotyping scheme to biotype strains into additional enzyme biotypes.

Reliability of two commercial serological kits for serodiagnosing Helicobacter pylori infection.

Two commercial serological kits, Pylori-set (Orion Diagnostica, Finland) and Helico-G (Cambridge Biomedical Ltd, UK), and an in-house ELISA were evaluated with sera from 24 Helicobacter pylori-positive and 146 H. pylori-negative dyspeptic patients. Sensitivity, specificity, positive and negative predictive values of Pylori-set were lower than that of Helico-G and in-house ELISA. Helico-G was more sensitive (91.7%) than in-house ELISA (83.3%) and both had comparable negative predictive values of 98.3% and 97.3%, respectively. However, specificity (97.9%) and positive predictive value (86.9%) of an in-house ELISA were much higher than specificity (80.1%) and positive predictive value (43.1%) of Helico-G. Kappa index of agreement between the three serological tests (Pylori-set, Helico-G or in-house ELISA) and the presence of H. pylori in antral biopsies was very low (k = 0.13; z = 1.9; p > 0.05), moderate (k = 0.49; z = 7.1; p < 0.0001), or substantial (k = 0.82; z = 10.8; p < 0.0001), respectively. Overall, statistical evaluations demonstrated that both commercial kits were not as reliable as the in-house ELISA for serodiagnosing H. pylori infection.