环孢素A缓释系统植入前房抑制鼠角膜移植免疫排斥反应机制的研究

目的　探讨前房植入环孢素A(cyclosporineA ,CsA)缓释系统抑制鼠角膜移植免疫排斥反应的机制。方法　 (1)环孢素A缓释系统的制备 :为CsA粉剂与已交酯 丙交酯 已内酯的三元共聚物混合体 ,每粒含环孢素A 0 5mg。 (2 )对 90只 (90只眼 )BALB c鼠 (受体 )行穿透性角膜移植术 ,将其分为A、B、C组 ,每组 30只。供体为C5 7BL 6鼠。A组术中鼠前房植入CsA缓释系统 ;B组术中鼠前房植入不含CsA的空白缓释系统 ;C组术后不作任何处理作为正常对照组。术后 3d用裂隙灯显微镜观察角膜植片情况 ,记录角膜植片免疫排斥反应发生的时间和程度。各组分别于术后 1、2、4及 6周随机取 2只鼠眼行组织病理学检查 ,并用CD4、CD8及CD11B单克隆抗体行免疫组织化学染色 ,观察各组T淋巴细胞的迁移和数量。结果　A组鼠角膜植片排斥时间平均 (35± 3)d ,较B、C组 (14± 3)d明显延长 (P <0 0 0 1)。前房植入的CsA缓释系统体积缩小前 ,A组角膜植片均保持透明 ;当前房植入的CsA缓释系统消失后 ,角膜出现免疫排斥反应 ,植片逐渐混浊、增厚、血管化。B、C组免疫排斥反应均在术后 2周发生。组织病理学和免疫组织化学检查 :A组在术后 14d仅于植床角膜可见少量CD+ 4 　和CD+ 8　细胞浸润 ,在虹膜和睫状体中未见CD+ 11B、CD+ 4 、CD+ 8　T淋     

细胞毒T淋巴细胞相关抗原4免疫球蛋白抑制鼠高危角膜移植免疫排斥反应的实验研究

目的　探讨细胞毒T淋巴细胞相关抗原 4免疫球蛋白 (CTLA4 Ig)对小鼠高危角膜移植免疫排斥反应的抑制作用及局部抗免疫排斥反应机制。方法　建立 5 0只BALB/c小鼠穿透性角膜移植动物模型。治疗组 (2 5只 ) :取C5 7BL/ 6小鼠角膜片 ,放置于 10 μg/mlCTLA4 Ig保存液中浸泡 2 4h后 ,移植到BALB/c小鼠。对照组 (2 5只 ) :植片不行任何处理。术后每 3d用裂隙灯显微镜检查植片情况 ,每周应用组织学和免疫组织化学方法检测植片中各种炎性细胞和淋巴细胞的变化。对出现排斥反应的角膜植片应用逆转录PCR(RT PCR)方法检测部分细胞因子的表达。另外 ,选择经CTLA4 Ig治疗、植片保持透明 6周以上的小鼠作为受体 ,接受来自C5 7BL/ 6小鼠皮肤的移植 ,当移植皮肤发生排斥时 ,进行迟发性超敏反应 (DTH)分析。结果　CTLA4 Ig治疗组角膜植片保持透明 >10 0d。对照组小鼠术后 14d内均发生免疫排斥反应。组织病理学检查显示 ,角膜移植术后 2周 ,CTLA4 Ig治疗组植片保持正常细胞结构 ,无明显炎性细胞和T淋巴细胞浸润 ;对照组的排斥植片有大量炎性细胞和T淋巴细胞浸润 (包括CD 4 ,CD 8及CD 11细胞 )。术后 2周发生免疫排斥的角膜植片中检测到白细胞介素 10 (IL 10 ) ,肿瘤坏死因子α(TNF α) ,γ干扰素 (IFN γ) ,B7及C     

肿瘤坏死因子相关凋亡诱导配体转基因治疗鼠角膜移植免疫排斥的研究

目的：探讨肿瘤坏死因子相关凋亡诱导配体（tumor necrosis factor-related apoptosis-inducing ligand,TRAIL）对角膜移植免疫排斥反应的作用。方法：选择受体BALB/c和供体C57BL/6小鼠,各32只。将其分为正常对照组、可溶性死亡受体5(soluble death receptor5,sDR5)浸泡组、TRAIL的重组腺病毒（Ad-TRAIL）转染组及绿荧光蛋白（green fluorescent protein,GFP）的重组腺病毒（Ad-GFP）转染组,每组8只。采用免疫组化技术分别对病毒接种后不同时间的体外角膜内皮细胞中TRAIL蛋白进行检测。将携带有Ad-TRAIL的供体C57BL/6小鼠角膜移植片移植到受体BALB/c小鼠眼上,观察术后角膜免疫排斥反应发生的时间及炎性反应强度,并检测免疫排斥的角膜移植片中CD4^ 及CD8^ T淋巴细胞的浸润情况。采用DNA原位缺口末端标记检测角膜移植片中的凋亡细胞。结果：Ad-TRAIL转染3d,50％以上内皮细胞TRAIL蛋白表达阳性;转染10-14d时,内皮细胞TRAIL蛋白表达程度最高;转染3周后,TRAIL蛋白表达阴性。正常对照组、sDR5浸泡组、Ad-TRAIL转染组及Ad-GFP转染组小鼠角膜移植术后发生免疫排斥反应的平均时间分别为17.1、12.3、22.0及17.4d;4个组间角膜免疫排斥反应时间比较,差异有显著意义（P=0.000）。排斥的角膜组织中可见CD4^ 及CD8^ T淋巴细胞浸润,凋亡细胞呈散在分布。结论：TRAIL能抑制小鼠角膜移植术后免疫排斥反应,延长免疫排斥反应发生的时间。     

角膜移植患者外周血中T细胞CD28分子的表达及其意义

目的　探讨角膜移植患者外周血T细胞及亚群CD2 8分子表达的变化及其意义。方法　于术前1d、术后第1、2、3、4周,应用流式细胞仪检测2 5例角膜移植患者外周血中CD2 8分子表达水平的变化。结果　角膜高血管化植床组患者术后外周血T细胞CD2 8分子表达比角膜无血管化植床组患者明显增高,也比术前明显增高(P <0 .0 1) ;6例发生排斥反应的患者均出于高血管化植床组;术后早期外周血T细胞中以CD4 + 细胞为主。结论　外周血T细胞CD2 8分子表达与角膜移植排斥反应关系密切,检测角膜移植患者外周血中的CD2 8分子表达可更早监测免疫排斥反应的发生     

TGF—β1对角膜上皮移植后CD4^＋,CD^＋8,CD25^＋和CD71^＋的影响

目的：为有效控制角膜移植术后排斥反应的发生,提高角膜移植成功率,我们在小鼠（BALB／c)角膜上皮移植术后应用TCF－β1,并观察其对外周血淋巴细胞亚群CD4^ ,CD8^ ,CD25^ ,CD71^ 活化的影响,为今后临床应用TGF－β1抑制角膜移植术后免疫排斥反应奠定基础。方法：采用CD4^ ,CD8^ ,CD25^ ,CD71^ 免疫荧光标记及流式细胞仪检测技术。分别对设立的阴性对照组,阳性对照组,同基因组,异体角膜上皮组及TGF－β1治疗组的BALB/c小鼠角膜上皮移植术后12d的外周血中CD4^ ,CD25^ ,CD8^ ,CD25^ ,CD4^ ,CD71^ ,CD8^ CD71^ 的表达进行分析,结果：BALB/c小鼠角膜上皮移植术后12d的外周血中CD25^ CD4^ ,CFD25% CD8^ ,CD71^ CD4^ 和CD71^ CD8^ 双阳性的T淋巴细胞均有显升高,术后经TGF－β1治疗后,上述细胞的数量明显受到抑制。CD25^ CD8^ ,CD71^ CD4^ 和CD71^ CD8^ 双阳性的T淋巴细胞均有显升高,术后经GF－β1治疗后,上述细胞的数量明显受到抑制。结论：角膜上皮移植术后应用TGF－β1可抑制特异性抗原介导的,以及非特异性炎疗诱诱导的移植排斥反应。     

TGF-β1 对角膜上皮移植后CD4+、CD8+、CD25+、CD71+的影响

目的 :角膜移植排斥反应是角膜移植失败的主要原因。方法 :为有效控制角膜移植术后排斥反应的发生 ,提高角膜移植成功率 ,我们观察了TGF β1对BALB/c小鼠角膜上皮移植术后外周血淋巴细胞亚群CD 4 、CD 8、CD 2 5、和CD 71活化的影响。研究中采用CD 4 、CD 8、CD 2 5、CD 71、免疫荧光标记及流式细胞仪检测技术 ,对BALB/c小鼠角膜上皮移植术后 12d的外周血中CD 4 、CD 8、CD 2 5、CD 71的表达进行分析。结果 :BALB/c小鼠角膜上皮移植术后 12d的外周血中CD 4 CD 2 5、CD 8CD 2 5、CD 4 CD 71、及CD 8CD 71双阳性的T淋巴细胞均有显著升高 ;术后经TGF β1治疗后 ,上述细胞的数量明显受到抑制。结论 :TGF β1可抑制特异性抗原介导的 ,以及非特异性炎症诱导的移植排斥反应     

Toll样受体2调节Th细胞极化对小鼠角膜移植排斥反应发生的影响

目的 探究Toll样受体2(Toll like receptor 2,TLR2)是否通过调节辅助性T细胞(T helper cells,Th)极化影响角膜移植排斥反应的发生.方法 取30只C57BL/6小鼠和30只TLR2基因敲除小鼠为受体,BALB/c小鼠为供体,在受体小鼠右眼行同种异体角膜移植术,分别为野生组和基因敲除组;取19只C57BL/6小鼠右眼行自体角膜移植术,为自体组.术后每周两次裂隙灯下观察植片水肿程度和透明度,参照Sonoda评分标准对排斥指数(reject index,RI)进行评分;术后14 d收集角膜.分别取9只C57BL/6小鼠和TLR2基因敲除小鼠作为野生对照组和基因敲除对照组,行常规HE染色和实时荧光定量PCR检测.结果 术后随时间变化各手术组植片水肿和混浊程度不一,以野生组最为严重.角膜RI评分显示术后7d、14 d、21 d,基因敲除组(0.80 ±0.83、0.90±0.55、1.35±0.99)低于野生组(1.55 ±0.94、2.25 ±0.97、2.55±1.19),差异均有统计学意义(P=0.008、0.000、0.000).HE染色显示,野生组角膜基质层出现水肿和大量炎性细胞;而基因敲除组和自体组炎症反应较轻.PCR检测显示,基因敲除组角膜Th1和Th17细胞因子(IFN-γ和IL-17)mRNA表达(1.94±0.34、2.62±0.30)比野生组(4.27±0.37、3.99±0.40)低,差异均有统计学意义(P=0.000、0.001);Th2细胞因子(IL-4)三组差异无统计学意义(P＞0.05).结论 敲除TLR2可能通过抑制Th向Th1和Th17极化,降低角膜移植排斥率.     

HLA-DRB_1基因配型与高危角膜移植排斥关系的回顾性研究

目的　评价 HL A基因配型在减少高危角膜移植免疫排斥反应中的作用。方法　对 91例高危穿透性角膜移植病例 ,术后双盲法进行供受体 HL A - DRB1 基因分型和临床观察 ,随访 12～ 2 6 mo,对其基因配型情况和术后排斥反应的关系进行回顾性分析。结果　 91例患者中 6 1例随访资料完整。其中 16例供受体有 1个基因位点相符 ,在这些配型良好的病例中 ,5例 (31.2 4% )发生免疫排斥反应 ,但随访期间无植片混浊 ;45例配型不好的患者中 ,术后 2 3例 (5 1.11% )发生免疫排斥反应 ,其中 5例发生了植片混浊。结论　 HL A- DRB1基因配型未能显著减少角膜移植术后的免疫排斥反应     

耐受型抗原递呈细胞对小鼠角膜植片免疫排斥的影响

目的建立小鼠同种异体角膜移植模型,观察静脉注入抗原递呈细胞对术后免疫排斥的影响。方法建立BALB/c→C57BL/6小鼠角膜移植模型。随机分2组,静脉注入耐受型或普通抗原递呈细胞。根据植片混浊评分,判断植片排斥情况。随机取两组小鼠脾脏检测CD4 NKT百分比和IL-10质量分数。结果与对照组相比,实验组移植排斥出现晚(19d±1.6d,P=0.009)。术后脾脏CD4 NKT百分比、IL-10质量分数相对恒定。结论小鼠角膜移植术后耐受型抗原递呈细胞静脉注射可延长植片存活时间。     

FOXP3在角膜移植免疫排斥反应中的作用

目的 探讨转录因子FOXP3在角膜移植免疫排斥反应中的作用.方法 建立角膜移植动物模型.将57只SD大鼠随机分为A组(正常组)、B组和C组(术后0、2、 4、 6、8 d分别球结膜下注射生理盐水和地塞米松注射液).用裂隙灯观察移植排斥情况,RT-PCR检测植片内FOXP3 mRNA的表达,流式细胞术检测移植术前和术后不同时间外周血CD4 CD25 T及CD4 FOXP3 T淋巴细胞的表达.对各组角膜植片进行CD4、CD8、CD25和FOXP3表达的免疫组织化学检测.结果 C组发生排斥反应时间较B组明显延迟(P<0.05),B组术后第11 d角膜植片内FOXP3 mRNA的表达较C组明显减弱(P<0.05),对照组CD4 CD25 T/CD4 T的表达明显高于术前(P<0.05),而CD4 FOXP3 T/CD4 T的表达明显低于术前(P<0.05),植片中CD4、CD8和CD25表达明显,FOXP3有一定的表达.角膜移植排斥反应期间,地塞米松治疗组FOXP3和CD4 FOXP3 T/CD4 T的表达明显增强,CD4 CD25 T/CD4 T的表达明显减弱.结论 FOXP3在角膜移植免疫排斥反应过程中发挥重要的作用;增强植片内FOXP3的表达或增加外周血CD4 CD25 Tr淋巴细胞的含量有助于抑制角膜移植免疫排斥反应的发生.     

CD8+ T cell-mediated delayed rejection of orthotopic guinea pig cornea grafts in mice deficient in CD4+ T cells

PURPOSE: To determine the immunopathogenesis of delayed orthotopic corneal xenograft rejection in mice deficient in the xenoreactive CD4+ T cells that mediate acute rejection. METHODS: CB.17 SCID and BALB/c mice were used as recipients of orthotopic cornea grafts obtained from strain 13 guinea pigs. Before transplantation, SCID recipients, which do not normally reject guinea pig cornea grafts, were reconstituted with spleen cells (whole, CD4-depleted, CD4/CD8-depleted) or purified CD8+ T cells from normal BALB/c donors. Graft survival was assessed by clinical examination, and median survival times (MST) were calculated. Lymphocytes from mice that rejected guinea pig cornea grafts were analyzed in vitro for their capacity to respond to guinea pig xenoantigens and to lyse guinea pig target cells. RESULTS: SCID mice reconstituted with whole spleen cells from BALB/c donors rejected guinea pig corneas with a vigor identical with that of normal BALB/c mice (MST = 15 and 14 days, respectively), whereas SCID mice reconstituted with CD4-depleted BALB/c spleen cells rejected guinea pig corneas in a delayed fashion (MST = 27 days), as did SCID mice reconstituted with purified CD8+ T cells from BALB/c donors. Although CD8+ T cells from rejector mice failed to lyse guinea pig target cells in vitro, the T cells proliferated and secreted IFN-gamma in response to in vitro stimulation with guinea pig xenoantigens. CONCLUSIONS: Guinea pig cornea xenografts that avoid acute rejection in CD4+ T cell-depleted mice are vulnerable to rejection by CD8+ T cells. Effector CD8+ T cells destroy corneal xenografts through release of proinflammatory mediators (IFN-gamma) rather than by cytotoxicity.     

Xenoreactive CD4+ T cells and acute rejection of orthotopic guinea pig corneas in mice

PURPOSE: To explore immunologic issues involved in orthotopic corneal xenotransplantation in a discordant combination using guinea pigs as donors and mice as recipients. METHODS: Two-millimeter-diameter guinea pig corneal buttons were transplanted into 1.5-mm-diameter graft beds on mouse corneas using 12 interrupted sutures. Eyelids were maintained occluded with tarsorrhaphy except at the times of clinical inspection. Grafts were considered to be rejected when the pupil margin was not visible clearly through the graft by slit-lamp microscopy. RESULTS: Guinea pig corneas protected from desiccation by persistent tarsorrhaphy survived indefinitely in the eyes of C.B-17SCID mice but were rejected acutely (but not hyperacutely) in eyes of normal BALB/c and C57BL/6 mice (median survival times, MST, 16 and 10 days, respectively). Graft survival was not extended in mice deficient in micro heavy chain or beta-2 microglobulin genes, slightly extended in mice deficient in the C3 gene (MST of 21 versus 17 days) and greatly extended in mice deficient in the CD4 gene (MST of 26 versus 9 days). Reconstitution of CD4 knock-out (KO) mice with CD4+ T cells promoted acute rejection of corneal xenografts. CONCLUSIONS: Hyperacute rejection does not occur in guinea pig corneal xenografts in mouse eyes, indicating that corneal xenografts are less vulnerable to this type of rejection than other solid tissue xenografts. CD4+ T cells are the primary mediators of acute graft rejection, although complement may contribute in a minor way. Neither antibodies nor CD8+ T cells participate in acute graft rejection. Because guinea pig cornea grafts in eyes of CD4KO mice are rejected in a delayed fashion, other innate and/or adaptive immune effectors must also be able to cause rejection of orthotopic corneal xenografts.     

Role of CD4+ T cells in immunobiology of orthotopic corneal transplants in mice.

PURPOSE: To determine, with the use of mice genetically deficient in expression of CD4 or CD8 molecules, which T cells are responsible for rejection of orthotopic corneal allografts in mice. METHODS: Corneas were prepared from major histocompatibility complex (MHC)-only incompatible, minor histocompatibility (H)- only incompatible, and MHC-plus-minor H incompatible donors and grafted orthotopically to eyes of CD4 knockout (KO), CD8KO, and wild-type control mice. Graft survival patterns were assessed clinically and compared. Mice that retained healthy corneal allografts beyond 8 weeks were evaluated for evidence of donor-specific tolerance and anterior-chamber-associated immune deviation (ACAID) using local adoptive transfer reactions and challenge with orthotopic skin allografts. RESULTS: Corneas grafted to CD8KO mice were rejected with an incidence and tempo indistinguishable from that in wild-type control animals. By contrast, MHC-only, and minor-H-only incompatible corneal grafts survived indefinitely in eyes of CD4KO mice. Approximately 50% of corneal grafts that confronted CD4KO recipients with both MHC and minor H alloantigens experienced delayed rejection, whereas similar grafts in wild-type recipients were rejected acutely. CD4KO mice with long-accepted grafts displayed neither donor-specific ACAID nor allograft tolerance. CONCLUSIONS: CD8+ T cells play little or no role in acute rejection of orthotopic corneal allografts. Instead, acute rejection is mediated almost exclusively by CD4+ T cells. Moreover, when corneal allografts survive for 8 weeks without acute rejection, CD4+ T cells promote donor-specific ACAID thereby insuring long-term graft acceptance.     

Preliminary study of the effect of FK506 nanospheric-suspension eye drops on rejection of penetrating keratoplasty.

OBJECTIVE: The aim of this study was to investigate the effect of a topical FK506 nanospheric suspension in a rat model of penetrating keratoplasty. METHODS: FK506 nanospheres were prepared by using a biodegradable poly (lactic-co-glycolic acid) copolymer (PLGA). Its distribution in the eye and blood after a single instillation was examined in rabbits. Sprague-Dawley (SD) rats received corneal heterografts and were topically treated with phosphate-buffered saline (PBS), PLGA, FK-506 0.01% (nanospheres), or dexamethasone 0.05% solutions twice a day for 28 days. Rejection index and graft-survival time were recorded and compared between the four groups. Three grafts were collected at different time points for immunohistochemical studies. RESULTS: In the cornea, the FK-506 concentration reached its peak within 1 h of a single eye-drop instillation and then decreased by half (1667.85 +/- 611.87 ng/g) at 8 h. FK-506 cannot be detected in rabbit blood. There were significant differences in the graft-survival time between the FK-506 nanosphere group (15.09 +/- 4.81 days) and the other three groups [PBS (7.90 +/- 1.20, t = -4.594, P < 0.001), PLGA (8.44 +/- 0.88, t = - 4.074, P = 0.001) and dexamethasone (10.44 +/- 1.42, t = -2.790, P = 0.012)]. The rejected corneas in the FK506 nanosphere group showed significantly fewer CD4, CD8, CD68, CD79, vascular endothelial growth factor, ICAM, and tumor growth factor-beta(1)-positive cells than those in the other groups. CONCLUSIONS: FK506 0.01% nanospheric-suspension eye drops delayed the occurrence of corneal allograft rejection and prolonged allograft survival time. The FK506 nanospheres may be valuable in suppressing corneal graft rejection.     

细胞毒性T淋巴细胞相关抗原4-凋亡相关蛋白配体双功能蛋白抑制小鼠角膜移植免疫排斥反应的研究

目的 探讨利用基因重组技术合成的细胞毒性T淋巴细胞相关抗原4(CTLA4)-凋亡相关蛋白配体(FasL)双功能蛋白预防小鼠角膜移植术后免疫排斥反应发生的疗效及其作用机制.方法 为实验研究.建立小鼠穿透性角膜移植动物模型,供体为C57BL/6小鼠(45只),受体为BALB/c小鼠(90只).利用随机分组法将实验动物分为3组,每组30只,A组即对照组(不进行任何治疗),B组即环孢素A缓释系统(CsA DDS)前房植入组,C组即10 μg/ml CTLA4-FasL双功能蛋白浸泡角膜植片组.术后比较3组间角膜植片的存活时间,并分别利用免疫组织化学检测CD4+T细胞,逆转录PCR(RT-PCR)检测CD80、CD86、白细胞介素10(IL-10)、肿瘤坏死因子α(TNF-α)、干扰素γ(IFN-γ)mRNA,DNA原位末端标记(TUNEL)检查凋亡的发生情况.结果 A、B、C组角膜植片的存活时间分别为(14.3±1.3)、(58.0±2.8)、(106.3±17.5)d.C与A组、C与B组、B与A组进行组间两两比较,差异均有统计学意义(均P=0.000).术后A组角膜植片中炎性细胞数量不断增加,以CD4+T细胞浸润为主;B组角膜植片中未见明显炎性细胞浸润;C组角膜植片中浸润的CD4+T细胞数量在术后7 d达到最多,之后发生骤减.RT-PCR检查可见在术后3 d A组和B组角膜和虹膜组织表达CD86 mRNA,术后7 d表达CD80 mRNA,而在相同时间点上C组均减弱表达CD86和CD80mRNA.术后14 d,A组发生排斥的角膜中可检测到IL-10、TNF-α、IFN-γ mRNA,B组和C组则检测不到上述细胞因子的表达.TUNEL检查显示术后7 d C组角膜和虹膜组织中分布着大量发生凋亡的单核细胞,而A、B组均未观察到细胞凋亡现象.结论 CTLA4-FasL双功能蛋白既能阻断T细胞活化所需的CD28-CD80/CD86共刺激信号途径,又能诱导T细胞凋亡,通过双重作用机制发挥免疫抑制作用,从而有效地延长角膜植片的存活时间.     

FK506抑制大鼠角膜移植免疫排斥反应的免疫病理学研究

目的 研究角膜移植免疫排斥反应的免疫病理学变化及免疫细胞和某些相关免疫分子在角膜移植免疫排斥反应中的作用,阐明了ＦＫ５０６的免疫抑制机理。方法 应用免疫组织化学染色方法检测ＦＫ５０６,环胞霉素Ａ及对照组角膜植片中ＣＤ＾＋４,ＣＤ＾＋８,巨噬细胞,白细胞介素－２受体,Ⅱ类主要组织相容性抗原,细胞间粘附分子－１及淋巴细胞功能相关抗原－１的表达。结果 排斥的角膜组织大表达上述免疫细胞和分子,ＦＫ５０６可     

Modulation of costimulation by CD28 and CD154 alters the kinetics and cellular characteristics of corneal allograft rejection

PURPOSE: To examine the effect of modulating the lymphocyte costimulation pathways through CD28 and CD154 (CD40 ligand) in a model of corneal allograft rejection, with particular interest in changes in the observed features of rejection. METHODS: CD28 knock-out (CD28KO) and wild-type BALB/c control mice received corneal grafts from fully major histocompatibility complex (MHC)-mismatched C3H donors and were treated with CTLA4-Ig and/or anti-CD154 Ab on days 0, 2, and 4 after transplantation. Proliferation of BALB/c and CD28KO T cells in response to C3H stimulators was examined in a mixed lymphocyte reaction (MLR) in the presence of CTLA4-Ig or anti-CD154 Ab. RESULTS: Corneal allograft survival in wild-type BALB/c mice (median survival time [MST] 14 days) was significantly prolonged by blockade of the costimulatory pathways with CTLA4-Ig or anti-CD154 Ab (MST 21 days and 25 days respectively). MST in recipients treated with CTLA4-Ig and anti-CD154 Ab in combination was 29 days, not significantly longer than graft survival in single-treatment groups. MST in CD28KO recipients was 46 days and was not prolonged after treatment with anti-CD154 Ab (MST, 43 days). A similar result was found in the MLR, in which anti-CD154 Ab had no effect on proliferation of CD28KO compared with wild-type T cells. In CTLA4-Ig-treated CD28KO, grafts were rejected at an accelerated tempo, similar to that in wild-type BALB/c recipients (MST 16 days). More severe graft injury after the onset of rejection in untreated allograft recipients was accompanied by a higher number of graft-infiltrating CD45(+) cells, but similar proportions of CD4(+) and CD8(+) cells. CONCLUSIONS: CD28- and CD154-mediated costimulation have significant functional roles in corneal allograft rejection. Agents that modulate CD28 and CD154 pathways delay onset and reduce the severity of observed allograft rejection. However, their use in combination did not have an additive effect, MLR data indicating that the CD40-CD154 system depends on a functioning CD28 costimulatory pathway.