Coito A J, Binder J, Brown L F, de Sousa M, Van de Water L, Kupiec-Weglinski J W
Harvard Medical School, Department of Surgery, Brigham and Women's Hospital, Boston, MA 02115.
J Immunol. 1995 Mar 15;154(6):2949-58.
Extracellular matrix (ECM) components provide costimulatory signals for T cell activation in vitro, and may be critical for lymphocyte migration and tissue positioning in vivo. We conducted a series of studies in rat recipients of cardiac allografts to evaluate intragraft expression of a prominent ECM protein, fibronectin (FN), and to analyze the effects of infusing a neutralizing anti-TNF-alpha serum on FN expression and lymphocyte migration into the transplants. LBNF1 cardiac allografts were rejected within 8 days in control LEW rats. A prominent immunohistochemical feature of this immune response was the dense deposition of FN at the graft site as early as 3 h, which then peaked at 4 to 6 days. The early 3-h FN deposition (likely plasma FN) was noted before cellular infiltration. Northern blot analysis established that a marked induction of FN mRNA expression occurred in rejecting cardiac allografts at day 4 after transplantation. To determine the source of FN mRNA, we conducted a series of in situ hybridization studies with probes for FN and lysozyme, a macrophage-specific marker. Indeed, the majority of graft-infiltrating cells expressed lysozyme mRNA and FN mRNA. Administration of anti-TNF-alpha serum into LEW hosts (0.5 ml i.v. at days 1 and 3 only) abrogated acute rejection and prolonged cardiac allograft survival to approximately 13 days. This was accompanied by depressed circulating and intragraft TNF-alpha levels, and markedly down-regulated FN mRNA/protein expression patterns, as compared with those in recipients given nonimmune rabbit serum. Anti-TNF-alpha treatment also markedly decreased graft infiltration by ED1+ monocytes/macrophages, OX-8+, and VLA-4+ cells, normally peaking at 4 days. Moreover, we found that the migration of 111In-labeled specifically sensitized lymph node lymphocytes to cardiac allografts in secondary rat recipients conditioned with anti-TNF-alpha serum was significantly decreased, as compared with that in controls. Thus, FN expression by intragraft macrophages occurs within the same interval as cellular infiltration, and may act as an ECM component "signal" for selective homing of recirculating lymphocytes in graft recipients. The results of this study support the notion that in vivo interactions between mononuclear cells and ECM may be vital for the ingress of alloreactive lymphocytes at the graft site, and offer potential novel sites for therapeutic intervention in the control of transplant rejection.
细胞外基质（ECM）成分在体外为T细胞活化提供共刺激信号，并且可能对体内淋巴细胞迁移和组织定位至关重要。我们在心脏同种异体移植的大鼠受体中进行了一系列研究，以评估一种重要的ECM蛋白纤连蛋白（FN）在移植组织内的表达，并分析输注中和性抗TNF-α血清对FN表达以及淋巴细胞向移植物内迁移的影响。在对照LEW大鼠中，LBNF1心脏同种异体移植物在8天内被排斥。这种免疫反应的一个显著免疫组织化学特征是早在3小时时FN就在移植部位密集沉积，然后在4至6天达到峰值。在细胞浸润之前就观察到了早期3小时的FN沉积（可能是血浆FN）。Northern印迹分析表明，移植后第4天，在排斥的心脏同种异体移植物中FN mRNA表达明显诱导。为了确定FN mRNA的来源，我们用FN和溶菌酶（一种巨噬细胞特异性标志物）的探针进行了一系列原位杂交研究。实际上，大多数移植浸润细胞表达溶菌酶mRNA和FN mRNA。仅在第1天和第3天静脉内给予LEW宿主抗TNF-α血清（0.5 ml）可消除急性排斥反应，并将心脏同种异体移植物存活期延长至约13天。与给予非免疫兔血清的受体相比，这伴随着循环中和移植组织内TNF-α水平降低，以及FN mRNA/蛋白表达模式明显下调。抗TNF-α治疗还显著减少了ED1 +单核细胞/巨噬细胞、OX-8 +和VLA-4 +细胞的移植浸润，这些细胞通常在4天达到峰值。此外，我们发现，与对照组相比，在用抗TNF-α血清预处理的二级大鼠受体中，111In标记的特异性致敏淋巴结淋巴细胞向心脏同种异体移植物的迁移明显减少。因此，移植组织内巨噬细胞的FN表达与细胞浸润发生在同一时间段内，并且可能作为一种ECM成分“信号”，用于移植受体中再循环淋巴细胞的选择性归巢。本研究结果支持这样的观点，即体内单核细胞与ECM之间的相互作用对于同种异体反应性淋巴细胞进入移植部位可能至关重要，并为控制移植排斥反应提供了潜在的新的治疗干预位点。
