What is the role of infection in the pathophysiology of Behçet disease?

Updated: Dec 21, 2020
  • Author: Nicole Davey-Ranasinghe, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

Exposure to an infectious agent may trigger a cross-reactive immune response. Proposed infectious agents have included the following:

The International Study Group for Behçet's Disease has emphasized the presence of recurrent oral ulcers as a primary consideration in the diagnosis of Behçet disease. [3] In response, the pathogens above have been targeted for study, with the hope of establishing a direct link between their presence and disease activity. Unfortunately so far, researchers have been unable to generalize results across geographic populations.

The study of heat shock proteins (HSPs) has provided some insight into possible mechanisms that contribute to the development of Behçet disease. Through discovery that human HSP-60 and HSP-65 share greater than 50% homology with mycobacterial HSP, enhanced T-cell response has been elicited with exposure to both bacterial and human homogenates in Behçet disease patients compared with controls in United Kingdom, Japanese, and Turkish populations.

HSP-65, found in high concentrations in oral ulcers and active skin lesions in patients with Behçet disease, has also been demonstrated to stimulate production of antibodies that exhibit cross-reactivity with streptococcal species present in the mouth. [6, 7, 8] Feng et al suggested that HSP-A6 levels may be useful in differentiating intestinal Behçet disease from Crohn disease: in their study, serum HSP-A6 expression was significantly elevated in intestinal Behçet disease (0.72 ± 0.39 ng/mL) compared with Crohn disease (0.50 ± 0.24 ng/mL, P = 0.000) and healthy controls (0.38 ± 0.37 ng/mL). [9] The clinical relevance of enzyme-linked immunosorbent assay (ELISA) testing to measure HSPA6 is currently unknown.

Attempts at determining whether tissue antigens have a role in channeling the immune response have been unsuccessful. Elevated peripheral levels of gamma-delta T cells (γδ+ T cells) in patients with Behçet disease in response to exposure to mycobacterial HSPs compared with those in healthy subjects imply a role for their production. [10] Antigen-driven expansion of oligoclonal Vβ+ T-cell receptor (TCR)–specific cell lines in Behçet disease patients has been demonstrated. [11] However, generalization of these results is not applicable because of the high degree of interindividual variability in TCR expression.


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