Expression of IFN-γ, IL-4, and IL-17 in cutaneous schistosomal granuloma

Cutaneous schistosomal granuloma (CSG) is a rare dermatological disease, the clinical and histopathological features of which are well defined. Although a panoramic picture of its immunopathogenesis in humans is not yet available, it is believed to be induced by T helper 1 (Th1), Th2, or Th17 cytokines in animals. This study evaluated the expression of different types of Th cytokines, including Th1 cytokine interferon-γ (IFN-γ), Th2 cytokine interleukin-4 (IL-4), and Th17 cytokine IL-17, in human CSG.

This study included nine patients with CSG. Dermatological examinations were conducted in all subjects. Skin biopsy specimens were stained with hematoxylin and eosin (H&E). Immunohistochemical examination was performed using three monoclonal anti-human antibodies against IFN-γ, IL-4, and IL-17 to evaluate Th1, Th2, and Th17 cytokines, respectively.

The most common site of CSG manifestation was the paraumbilical area, which was affected in 66.7% of patients. All lesional skin biopsy specimens revealed multiple dermal granulomas surrounding schistosomal eggs. Positive immunoreactivity for IFN-γ, IL-4, and IL-17 was present in dermal inflammatory infiltrate in 88.9, 11.1, and 88.9% of subjects, respectively. There were statistically significant negative correlations between the duration of disease and both IFN-γ and IL-17 (P ≤ 0.05), and a statistically significant positive correlation between IFN-γ and IL-17 (P ≤ 0.05).

This study suggests that CSG is formed by the action of both Th1 (IFN-γ) and Th17 (IL-17) cytokines, which have been shown to be directed against the schistosomal egg to induce a cell-mediated immune response.