Immune defense mechanisms of the dentin/pulp complex. An immunological and molecular biological analysis

为探讨牙髓致密细胞（DCs）在牙髓疾病发病机制中的作用，采用免疫组织化学和分子生物学方法对其进行了研究。主要研究结果如下：1.在人牙无牙髓炎的牙本质龋中，表达HLA-DR的牙髓DCs在受影响的牙本质小管下表现出局部积聚。在有浅龋损的牙齿中，积聚是明显的。牙髓DCs大多表达CD 14和CD 68。在深龋病变的牙齿中，在一些DC上检测到CD 83和CD 86的表达。T细胞显示出显着增加牙齿浅牙本质龋。这些T细胞主要是表达CD 45 RO的记忆细胞，其中一些共表达活化T细胞的标志物CD 25。然而，B细胞仅在牙本质深龋的牙齿中显示出增加。这些结果表明DC-T细胞相互作用和随后的T细胞活化参与了牙髓疾病的初始发病机制.用逆转录聚合酶链反应（RT-PCR）检测诱导型一氧化氮合酶（iNOS）mRNA在LPS诱导的大鼠上切牙牙髓炎中的表达，发现iNOS mRNA在LPS诱导的牙髓炎中表达最强，在6 h时达到高峰。免疫组织化学染色显示，大鼠iNOS阳性细胞大多数是巨噬细胞。环氧化酶-2（考克斯-2）和促炎细胞因子的mRNA表达在3至6小时达到峰值，而IL-10（抗炎细胞因子）mRNA在6小时首次检测到。给药诱导型一氧化氮合酶抑制剂导致炎症牙髓中考克斯-2和炎性细胞因子的mRNA表达急剧下降。提示巨噬细胞产生的NO可能参与牙髓炎症反应的调节。

Immunohistochemical and molecular biological analyzes were conducted in order to investigate the roles of pulpal densritic cells (DCs) in the pathogenesis of pulpal diseases. Results obtained were as follows:1. In human teeth bearing pulp exposure-free dentinal caries, HLA-DR-expressing pulpal DCs exhibited a localized accumulation beneath the affected dentinal tubules. The accumulation was evident in teeth with a shallow carious lesion. The majority of'the pulpal DCs expressed CD14 and CD68. In teeth with a deep carious lesion, expression of CD83 and CD86 was detected on some DCs. T cells showed a marked increase in teeth with shallow dentinal caries. These T cells were mostly memory cells expressing CD45RO, and some of them co-expressed CD25, a marker for activated T cells. However, B cells showed an increase only in teeth with deep dentinal caries. These results suggest that DC-T cell interaction and subsequent activation of T cells are involved in the initial pathogenesis of pulpal diseases.2. Expression of inducible nitric oxide synthase (iNOS) mRNA in LPS-induced pulpitis of rat upper incisors peaked at 6 hrs, which was detected by means of reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemical staining for rat iNOS revealed that most of the iNOS-positive cells were macrophages. The expression of mRNAs for cyclooxygenase-2 (COX-2) and pro-inflammatory cytokines peaked at 3 to 6 hrs, whereas IL-10 (anti-inflammatory cytokine) mRNA was first detected at 6 hrs. Administration of an iNOS inhibitor caused drastic decrease in the expression of mRNAs for COX-2 and inflammatory cytokines in the inflamed pulp. These results indicate that NO generated by macrophages may regulate the pulpal inflammatory reactions.