[The 69th annual meeting symposium. II: Mechanism of necrotizing granuloma formation and its function]

Histological features of tuberculosis are caseation necrosis and epithelioid cell granuloma formation. Both phenomena are interpreted as expression of cellular immunity. Caseation necrosis is thought to be immunopathology and epithelioid cell granuloma formation is considered to be expression of protective immunity. Recently roles of cytokines for granuloma formation are gradually elucidated. In this symposium, mechanisms and functions of necrosis and granuloma formation Dr. Akagawa reported differentiation of two types of phenotypically different macrophages from human monocytes by GM (granulocyte-macrophage)-CSF or M (macrophage)-CSF. Interestingly such a basic differentiation induced by CSF was affected by IL-4 (interleukin-4). Langerhans-like dendritic cells were generated by cooperation of GM-CSF and IL-4, and multinucleated cells were generated by cooperation of IL-4 and M-CSF. Dr. Fukuda reported human Langerhans cell granulomatosis (LCG) from the pathological and immunohistochemical standpoints. In situ proliferation of LCs in the LCG was demonstrated by immunohistochemistry using antibody to PCNA (proliferating cell nuclear antigen) which is used to detect proliferating cells. In the course of granuloma formation, damage and disruption of lung structure such as alveolar basement membrane and elastic tissue framework, and reactive intraluminar fibrosis was observed. Mechanism of cystic dilation was also reported. Cytokines might play important roles in these events. Dr. Ina demonstrated experimental epithelioid cell granuloma formation. Extract (granuloma inducing factor, GIF) from Schistosoma mansoni Egg-induced granuloma, TNF -alpha, or IL-1 beta were coated, individually on the surface of beads, then these beads were inoculated to rat's skins or cultured with rat's monocytes. Four weeks later, epithelioid cell granuloma was demonstrated histologically and electronmicroscopically around beads in vitro and in vivo. GIF-induced granuloma was more organized than cytokine-induced ones. In vitro using human monocytes, activated macrophages accumulated around beads of which cytokines or GIF were coated. It was suspected that many cytokines or other factors are needed to make epithelioid cell granuloma. Dr. Sakamoto showed the presence of acid fast bacilli and various inflammatory cells including lymphocytes and macrophages in the tuberculous caseous necrosis after exudative reaction (E-necrosis) by immunohistochemistry. But no acid fast bacilli or inflammatory cells were found in the caseous necrosis after productive reaction (P-necrosis). TNF-alpha (tumor necrosis factor-alpha) and IL-4 were stained in the E-necrosis and IL-4 and ICAM-1 (intercellular adhesion molecule-1) were positively stained in the cytoplasm of epithelioid cells by immunohistochemistry. It was suspected that many cells and cytokines were involved in epithelioid cell granuloma formation and caseous necrosis formation.(ABSTRACT TRUNCATED AT 400 WORDS)