Persistence of local cytokine production in shigellosis in acute and convalescent stages

Abstract

Shigella infection is accompanied by an intestinal activation of epithelial cells, T cells, and macrophages within the inflamed colonic mucosa. A prospective study was carried out to elucidate the cytokine pattern in Shigella infection linked to development of immunity and eradication of bacteria from the local site and also to correlate the cytokine profile with histological severity. An indirect immunohistochemical technique was used to determine the production and localization of various cytokines at the single- cell level in cryopreserved rectal biopsies from 24 patients with either Shigella dysenteriae type 1 (n = 18) or Shigella flexneri (n = 6) infection. The histopathological profile included presence of chronic inflammatory cells with or without neutrophils and microulcers in the lamina propria, crypt distortion, branching, and less frequently crypt abscesses. Patients had significantly higher (P < 0.005) numbers of cytokine producing cells for all of the cytokines studied, interleukin-lα (IL-lα), IL-1β, IL-1ra, tumor necrosis factor alpha (TNF-α), IL-6, IL-8, IL-4, IL-10, gamma interferon, TNF-β, and transforming growth factor β1-3, in the biopsies than the healthy controls (n = 13). The cytokine production profile during the study period was dominated by IL-1β, transforming growth factor β1-3, IL-4, and IL-10. Significantly increased frequencies of cytokine-producing cells (P < 0.05) were observed for IL-1, IL-6, gamma interferon, and TNF-α in biopsies with severe inflammation in comparison with those with mild inflammation. During the acute stage of the disease, 20 of 24 patients exhibited acute inflammation in the rectal biopsies and the cellular infiltration was still extensive 30 days after the onset of diarrhea, although the disease was clinically resolved. In accordance with the histological findings, cytokine production was also upregulated during the convalescent phase; there was no significant difference (P > 0.05) in the incidence of cytokine-producing cells between acute (2 to 8 days after the onset of diarrhea) and convalescent (30 days after onset) stages.