Interferon-gamma, interleukin-18, monokine induced by interferon-gamma and interferon-gamma-inducible protein-10 in histiocytic necrotizing lymphadenitis

Apoptosis of histiocytes is a characteristic feature of necrotizing lymphadenitis (HNL). Recent studies have indicated that Fas and perforin-based pathways are involved in the apoptotic process of HNL. Elevated levels of serum interferon (IFN)-γ are reported in HNL. The CXC chemokine interferon-γ-inducible protein-10 (IP-10) and monokine induced by interferon-γ (MIG) cause tissue necrosis, and interleukin (IL)-18 induces the expression of IFN-γ and Fas ligand (FasL) by T and natural killer (NK) cells. This study was designed to determine the expression of IFN-γ, IL-18, MIG and IP-10 in HNL. Ten cases of HNL were analyzed by using immunohistochemical staining and/or reverse transcriptase-polymerase chain reaction (RT-PCR). As a control, we included four cases of non-specific lymphadenitis. MIG and IP-10 proteins, which enhance the release of granzyme, showed a similar distribution pattern in viable tissues surrounding dead tissue, mostly within histiocytes, and lymphocytes in HNL. IL-18 was located within histiocytes, especially phagocytic histiocytes, but not within lymphocytes. In addition, IFN-γ-positive lymphocytes were frequently detected in the surrounding dead tissue, and the lymphocytes in the same area were frequently positive for CXCR3, a specific receptor of MIG and IP-10. In non-specific lymphadenitis, MIG, IP-10 and IL-18 positive cells were detected, but their numbers were relatively small compared with HNL, while IFN-γ positive cells were rarely encountered. Our findings suggest that the cytokine and chemokine pathways of IFN-γ, IL-18, MIG and IP-10 play an important role in the pathogenesis of apoptosis associated with HNL.