Decreased gut-associated IgA levels in patients with typhoid fever.

Gut and serum immune responses were studied in twenty-two patients with bacteriologically proved typhoid fever at different stages of the illness and six volunteers after parenteral immunizations with heat-killed typhoid vaccine. Whereas the former group had some specific antibodies in their intestinal aspirates and significant specific antibody responses in their sera, the latter could only mount a serum antibody response. Moreover, the intestinal IgA levels in the patients remained significantly decreased throughout the whole course of the illness, but a rise of IgG and IgM was observed in their jejunal secretions. In contrast, the levels of all the three major classes of serum immunoglobulins IgG, IgM and IgA were raised in the patients, as opposed to the volunteers, in whom only IgG and IgM levels were increased. It was inferred that the subjects with deficit of intestinal IgA, and thus lacking protective mucosal barrier, are more prone to develop typhoid fever.