Maintenance of acquired resistance to Mycobacterium tuberculosis by L form mycobacteria macrophages

本研究是为了证明我们的假设，即人类对结核分枝杆菌的长期获得性耐药归因于位于肉芽肿病变处的巨噬细胞将结核分枝杆菌转化为l型结核分枝杆菌。为了确定分枝杆菌能否在体内转化为L型，我们采用小鼠卡介苗感染模型。结果表明：1)感染60 d后，卡介苗在卡介苗小鼠体内转化为L型，用异烟肼（INH）处理感染卡介苗小鼠可诱导卡介苗转化为L型。2)原位pcr在肺肉芽肿病变的单核细胞中检测到L型卡介苗。3)ifn - γ参与了细胞内卡介苗转化为L型的过程。用L型卡介苗免疫或定植L型卡介苗的小鼠对静脉注射致死剂量的卡介苗感染具有免疫力。5)用雌激素或tnf - α处理L型卡介苗定植的小鼠，可使L型卡介苗向亲本卡介苗转化。这种逆转与tnf - α和tgf - β的生成增强有关。6) L型定植小鼠经静脉注射致死剂量卡介苗感染后，IL-1、IL-12和ifn - γ mrna强烈表达。这些数据有力地表明，将卡介苗转化为L型有助于维持对致死剂量卡介苗感染的获得性抗性。这种机制可能适用于可以持续很长时间的人类分枝杆菌免疫。

The present study was done to prove our hypothesis that long-lived acquired resistance of humans to Mycobacterium tuberculosis is ascribed to the transformation of M.tuberculosis into L-form M.tuberculosis in macrophages localized at granulomatous lesions. To determine whether mycobacteria can transform into L forms in vivo, murine BCG infection model was used.Results obrtained herein were as follows :1) BCG transformed into L forms in Bcg^r mice after 60 days of infection, and treatment of infected Bcg^s miced with isoniazid (INH) induced the transformation of BCG into L forms.2) L-form BCG was detected in mononuclear cells of granulomatous lesions in the lung by the in-situ PCR.3) IFN-gamma was responsible for the transformation of intracellular BCG into L forms.4) Bcg^s mice immunized with L-form BCG or colonized with L-form BCG were immune from an intravenous infection with a lethal dose of BCG.5) Reversion of L-form BCG to parental BCG was achieved by treating L form-colonized mice with estrogen or TNF-alpha. This reversion was associated with the enhanced production of TNF-alpha and TGF-beta.6) In L form-colonized mice, mRNAs for IL-1, IL-12 and IFN-gamma were strongly expressed after an intravenous infection with a lethal dose of BCG.These data strongly suggest that transformation of BCG into L forms contribute to the maintenance of acquired resistance to infection with a lethal dose of BCG.Such a mechanism is possibly applied to human mycobacterial immunity which can last over a long period.