The gastrointestinal tract is essential to host defence, acting as a b
arrier to absorption and translocation of gut antigens, including bact
eria. In experimental models, protein malnutrition is permissive to gu
t barrier failure and endogenous infection. A clinical correlate has n
ot been described. Intestinal morphology and barrier function to food
protein antigens was studied in malnourished patients. Thirty-five ind
ividuals were evaluated, 20 malnourished patients and 15 well nourishe
d hospital controls. Morphology was assessed from endoscopic biopsies
of the second part of the duodenum, and serum immunoglobulin (Ig) G an
tibodies to gliadin and beta-lactoglobulin were measured. No antibody
to food proteins was evident in the control group. In contrast, serum
IgG antibodies to at least one antigen were present in 15 malnourished
patients and to both antigens in ten (P<0.0001 versus controls). Seve
rely malnourished patients were more likely to have both antibodies pr
esent than those with mild or moderate malnutrition (P<0.05). Antibody
-positive malnourished patients had significantly better nutritional s
tatus than antibody-negative patients with malnutrition (P<0.05). In n
o group of patients was there morphological evidence of abnormal mucos
a or an immunological infiltrate. Gut barrier function is compromised
in malnourished patients which suggests a mechanism that may facilitat
e gut-derived infection and sepsis.