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，进行了免疫组织化学和分子生物学分析。研究结果如下：1.在有牙髓暴露的人牙本质龋齿中，表达人类白细胞抗原-DR的牙髓树突状细胞在受影响的牙本质小管下局部聚集。在有浅表龋损的牙齿中积聚明显。大多数牙髓树突状细胞表达CD14和CD68。在深面龋损的牙齿中，CD83和CD86在部分DC上表达。浅面牙本质龋齿中T细胞明显增多。这些T细胞大多是表达CD45RO的记忆细胞，其中一些细胞共表达CD25，CD25是活化T细胞的标志。然而，B细胞仅在有深牙本质龋齿的牙齿中表现出增加。这些结果提示DC-T细胞相互作用和随后T细胞的激活参与了牙髓疾病的初始发病机制。逆转录-聚合酶链式反应(RT-PCR)检测大鼠上切牙牙髓组织中诱导型一氧化氮合酶(INOS)mRNA的表达在6h达到高峰。大鼠iNOS免疫组织化学染色显示，iNOS阳性细胞多为巨噬细胞。环氧合酶-2(COX-2)和促炎细胞因子的mRNAs表达在3~6h达到高峰，而IL-10(抗炎细胞因子)的mRNAs在6h首次检测到。给予iNOS抑制剂后，炎症牙髓中COX-2和炎性细胞因子的mRNAs表达显著减少。提示巨噬细胞产生的NO可能对牙髓炎症反应有调节作用。

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.