Mannose-sensitive interaction of Escherichia coli with human peripheral leukocytes in vitro

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Abstract
The ability of Escherichia coli which possess or lack mannose-sensitive adherence factors (adhesins) to associate with human peripheral leukocytes in vitro in the absence of serum was studied. E. coli 19+, which have mannose-sensitive adhesins, were derived from E. coli strain 19 by culturing in static Trypticase soy broth at 37 degrees C. E. coli 19-, which lack mannose-sensitive adhesins, were derived from E. coli 19 by culturing in agitated Trypticase soy broth at 30 degrees C. E. coli 19+ attached to leukocytes and stimulated the release of lysozyme but not beta-glucuronidase or lactate dehydrogenase. In contrast, E. coli 19- showed poor attachment to the leukocytes and failed to stimulate lysosomal enzyme release. During a 60-min incubation with the leukocytes, the number of viable 19+ organisms decreased, whereas the number of viable 19- remained constant. Purified type 1 pili from E. coli 19+ agglutinated the leukocytes but did not stimulate lysosomal enzyme release. Pretreatment of leukocytes with type 1 pili failed to prevent the adherence of E. coli 19+. The association of 19+ with leukocytes and subsequent release of lysozyme could be blocked by alpha-methyl-D-mannoside but not by equivalent concentrations of dextrose and sucrose. These results show that mannose-sensitive adhesins on E. coli mediate association of the organisms with leukocytes in the absence of serum components. The identity of the adhesins involved in leukocyte association has yet to be determined.