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Infect. Immun., Jul 1996, 2794-2798, Vol 64, No. 7
V Friman, I Adlerberth, H Connell, C Svanborg, LA Hanson and AE Wold
Most Escherichia coli isolates can express type 1 fimbriae with mannose-
specific adhesins. These adhesins bind to the oligosaccharide chains of
secretory immunoglobulin A (IgA). Thus, in addition to specific antibody
activity, secretory IgA possesses a broad reactivity with bacteria
expressing type 1 fimbriae. The absence of secretory IgA in colonic
secretions, as seen in IgA deficiency, might therefore alter the ability of
type 1-fimbriated E. coli to colonize the large intestines of these
individuals. In the present study, 10 E. coli isolates from each of 17
IgA-deficient and 17 age-matched control individuals were assessed for the
carriage of the fim gene cluster by DNA-DNA hybridization and for the
expression of type 1 fimbriae by hemagglutination of guinea pig
erythrocytes. The contribution of type 1- fimbria-mediated adherence to
HT-29 colonic cells was also analyzed. The proportion of fim+ E. coli
isolates was lower in IgA-deficient than in control individuals (74 versus
94%, P < 0.05), as was the proportion of isolates expressing type 1
fimbriae in vitro (69% versus 85%, P < 0.05). The median
mannose-sensitive adherence to HT-29 cells was lower for isolates from
IgA-deficient individuals than from the controls (9 versus 26 bacteria per
cell, P < 0.05). Isolates expressing type 1 fimbriae showed lower
adherence to HT-29 cells when they were derived from IgA-deficient
individuals than when they were derived from control individuals (15 versus
27 bacteria per cell, P < 0.05). The results suggest that the
interaction of type 1 fimbriae with secretory IgA contributes to the large
intestinal colonization by these bacteria.
Copyright © 1996, American Society for Microbiology
Decreased expression of mannose-specific adhesins by Escherichia coli in the colonic microflora of immunoglobulin A-deficient individuals
Department of Clinical Immunology, Goteborg University, Sweden.
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