세균 초항원에 의해 활성화된 대식세포에서 Toll-like receptor의 발현양상
Expression of Toll-like Receptors on the Macrophages Activated by Bacterial Superantigens
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목 적 : 대표적인 세균 초항원인 포도알균 창자독소 B(SEB)에 의한 면역세포 활성에 Toll-like receptor (TLR)의 관련성을 알아보고, 지질다당질(LPS)에 의한 TLR의 발현양상과 비교하여 보았다. 재료 및 방법 : 세균 초항원인 SEB를 dye ligand affinity chromatography법으로 순수분리정제한 뒤 사람 말초혈액 단핵구와 사람 대식세포주인 THP-1을 자극하여 이들 세포에서 TLR1-9의 mRNA의 발현을 역전사중합효소반응법으로 확인하였고, 또한 LPS 자극에 의한 발현 양상과 비교하여 보았다. 결 과 : SEB로 사람 말초혈액 단핵구세포를 자극하였을 때 TLR1과 TLR5 mRNA 발현의 상승이 관찰되었고, TLR4 mRNA의 발현은 SEB 처리 후 1, 2시간째는 발현이 억제되다가 3시간 이후에 상승되는 양상을 보였다. 이런 TLR4 mRNA 발현의 변화는 말초혈액 단핵구를 LPS로 자극하였을 때도 유사하게 관찰되었고, SEB와 LPS를 동시에 자극하였을 때 더 현저한 변화를 보였다. 사람 대식세포주인 THP-1을 SEB 및 LPS로 자극하였을 때 TLR2 보다는 TLR4의 mRNA 발현에 현저한 변화를 관찰할 수 있었다. 결 론:이상의 결과로 SEB에 의한 사람 말초혈액 단핵구세포와 대식세포의 활성에 TLR의 연관성을 확인할 수 있었으며, 적어도 TLR4가 SEB에 대식세포 활성에 관여되었다. 또한 SEB와 LPS는 동시에 병용하여 단핵구세포를 자극하였을 때 상승적으로 TLR4 발현을 촉진할 것으로 추정된다. 향후 SEB 자극에 의한 대식세포 활성에 TLR의 관여 여부를 더 상세히 밝히는 것이 초항원에 의해 유발되는 질환들을 해결하는 중요한 열쇠가 될 수 있을 것으로 생각된다.
Abstract
Background:Staphylococcal enterotoxin B (SEB) as a prototype superantigen is known to play a pivotal role in toxic shock syndrome and severe sepsis. However, the precise mechanism initiating the activation of innate effector cells by SEB is unclear. Recently, Toll-like receptors (TLRs), the sensor of pathogen associated molecular pattern (PAMP), have been reported to be expressed abundantly in monocytic lineage-cells. The purpose of this study is to investigate whether TLRs are involved in the SEB-induced immune cell activation and to prove the differential TLRs expression in response to SEB and/or lipopolysaccharide (LPS). Materials and Methods:SEB was purified by dye ligand affinity chromatography. The mRNA expression of TLR1-9 in human peripheral blood mononuclear cells (PBMC) and human monocyte- like THP-1 cell line stimulated by SEB and/or LPS was detected by RT-PCR. Results:The treatment of PBMC with SEB elicited significant changes in the expression of several TLRs. Interestingly, the mRNAs of TLR1 and TLR5 were clearly up-regulated in PBMC, whereas mRNA of TLR4 was down-regulated in the very early period of stimulation within 1-2 hours, and subsequently up-regulated 3 hours later after the stimulation. The up-regulation of mRNA of TLR4 was detected in PBMC stimulated by LPS. The up-regulation was more prominent in the cells exposed concomitantly to SEB and LPS. The mRNA expression pattern of TLR4 in THP-1 cell line stimulated by SEB or LPS was comparable to those of PBMC. Conclusion:This study indicates that SEB triggers inflammatory signals on macrophages and PBMC by engaging TLRs, particularly TLR4. The combination of LPS and SEB synergistically modulates TLR4 signaling.
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