Immunopathology of Crohn's disease.

Available evidence indicates that pronounced stimulation of the local B-cell system is the major immunological alteration in Crohn's disease, and that a progressive deviation from the characteristic secretory IgA and IgM responses in favour of local IgG production occurs in association with increasing severity of the inflammatory process. Such an altered immunological homeostasis may contribute to the chronicity and relapse of the disease, but its possible involvement in the initiation of the lesion is unknown.