Clinical characteristics of lower extremity deep vein thrombosis in young vs. middle-aged adults: a single-center retrospective study.

Background: The incidence of deep vein thrombosis (DVT) in the lower extremities is increasing in the younger population. However, there are fewer reported comparisons in the literature for lower extremity DVT. Methods: Patients aged <40 years admitted with lower-extremity DVT between January 2018 and December 2023 were retrospectively analyzed and followed up for 1 year. Results: A total of 61 patients were included in the study and divided into two groups: 33 patients over 30 years of age (middle-aged group) and 28 patients under 30 years of age (young group). A significant gender difference was observed, with a higher proportion of males in the young group compared to the middle-aged group (P < 0.001). Five patients in the young group were treated with anticoagulation alone, whereas all patients in the middle-aged group underwent endovascular therapy. A higher prevalence of inferior vena cava thrombosis in the young group compared to the middle-aged group (60.71% vs. 33.3%, P = 0.032). The proportion of iliac vein stenosis was significantly higher in the middle-aged groups than in the young group (P = 0.002). There was no statistically significant difference in venous function scores (Villalta and rVCSS) between the two groups during both the preoperative period and the postoperative follow-up (P > 0.05). The incidence of lower-extremity DVT post-thrombotic syndrome and thrombus recurrence was higher in the young group than in the middle-aged group at 1 year postoperatively (PTS: 78.57% vs. 33.3%, P < 0.001, and thrombus recurrence: 28.57% vs. 9.09%, P < 0.05). Univariate and multivariate analyses revealed that inferior vena cava thrombosis was an independent risk factor for severe DVT post-thrombotic syndrome and recurrent DVT (P < 0.05), whereas gender was an independent risk factor for recurrent DVT (P < 0.05). Conclusions: This study suggests differences in the clinical characteristics and prognosis of lower-extremity DVT.

Endovascular repair of bilateral isolated common iliac artery aneurysms with unsuitable anatomy utilizing an aortic bifurcated unibody endograft and modified sandwich technique to preserve pelvic blood flow: a case series.

Bilateral isolated common iliac artery aneurysms (CIAAs) are rare, and endovascular repair of CIAAs has emerged as an alternative to traditional open surgical repair. The primary goal of therapy is to exclude the aneurysm sac while maintaining perfusion of at least one internal iliac artery (IIA) to prevent pelvic ischemia. Although the iliac branch device (IBD) has improved the feasibility of preserving the IIA, its applicability is limited to a specific subset of aneurysm anatomy. We present a case series of three patients with bilateral isolated CIAAs in whom preoperative CT scans revealed an absence of a landing zone, the diameter of proximal CIA diameter was less than 13.0 mm, and normal diameter of the nonaneurysmal infrarenal aorta, making it challenging to use an IBD alone or a standard bifurcated aortic endograft to provide a proximal landing zone for iliac artery stenting. To overcome the small diameter of the infrarenal aorta, we implanted an aortic bifurcated unibody endograft. Then, we utilized a balloon-expandable covered stent-graft with overdilation as a modified sandwich technique to create an "eye of the tiger" configuration to prevent gutter leakage. The final angiography performed during the procedure revealed successful exclusion of the aneurysms, with blood flow to the right IIA and no type III endoleak. During the postoperative follow-up period, no patients exhibited symptoms associated with pelvic ischemia. There were no endoleaks or sac expansions on the two-year follow-up CT scans, and all external and internal iliac graft limbs were patent. This study demonstrated that a combination of an aortic bifurcated unibody endograft and a modified sandwich technique can effectively treat bilateral isolated CIAAs with certain anatomical constraints.

Successful retrieval of tip-embedded inferior vena cava filter using a modified forceps technique: case report.

BACKGROUND: The retrieval of inferior vena cava (IVC) filter is essential for preventing complications associated with the device. Advanced techniques have been developed to improve the success rate of retrieving tip-embedded filters. The forceps technique is frequently used to address this issue. CASE PRESENTATION: We present a case study of two patients who underwent a successful tip-embedded IVC filter retrieval using a modified forceps technique, which has not been previously reported. This technique involves using a wire loop under the filter tip and a forceps to grasp the filter shoulder. By pulling the wire loop and pushing the forceps in counterforce, the filter tip is straightened and aligned with the vascular sheath. The vascular sheath can then dissect the filter tip out from the caval wall and get inside the sheath to complete the retrieval. CONCLUSIONS: The modified forceps technique we present here offers a new solution for the complex retrieval of IVC filters.

The Impact of Balloon Pre-dilatation Techniques on Drug-Coated Balloon Therapy for Femoropopliteal Artery Disease: Six-Month Results From the CIVILIAN Registry.

OBJECTIVE: The purpose of this study is to compare the initial outcomes of using the Chocolate balloon pre-dilatation (CLP) and sequential enlarging angioplasty pre-dilatation (sequential balloon pre-dilation [SP]) techniques versus the conventional balloon pre-dilatation (CP) method prior to drug-coated balloon (DCB) treatment for femoropopliteal (FP) lesions. METHODS: This was a retrospective analysis of prospectively collected data from the CIVILIAN (Clinical InVestigation of different lesIon preparation modaLIty followed by DCB in femoropopliteal Artery occlusioN disease) registry. Between March 2021 and November 2022, 3 pre-dilation techniques used prior to the DCB angioplasty were included. The study endpoint included intraoperative finial severe dissection after provisional stent placement, bailout stenting rate, the diameter of the largest pre-dilation balloon and DCB, as well as major adverse events (MAEs), including death, major limb amputation, or target vessel revascularization at 6 months. RESULTS: During the study period, 435 limbs (429 patients) were pre-dilated before DCB treatment in FP lesions, 166 limbs were pre-dilated with Chocolate balloons, 93 limbs with sequential enlarging balloon pre-dilation technique, and 176 limbs with CP. The largest pre-dilation balloon was significantly larger in CLP and SP groups than that in the CP group (CLP 4.74±0.52 mm vs CP 4.36±0.64 mm, p<0.001; SP 4.82±0.69 mm vs CP 4.36±0.63 mm, p<0.001). A consistent result was shown in DCB diameter (CLP 4.86±0.44 mm vs CP 4.71±0.51 mm, p=0.003; SP 4.90±0.58 mm vs CP 4.71±0.51 mm, p=0.006). The bailout stenting rate was significantly lower in the CLP group than that in the CP group (18.1% vs 30.1%, p=0.011). The rates of MAEs at 6 months in the CLP and SP groups were comparable to those in the CP group (7.2% and 8.6% vs 6.3%, p>0.05). The risk for intraoperative bailout stenting rate was related to TASC D classification (3.59, 95% CI: 1.83-7.05, p<0.001), chronic total occlusion (CTO) lesion (1.82, 95% CI: 1.07-3.10, p=0.028), as well as pre-dilated with the conventional balloon (1.64, 95% CI: 1.00-2.69, p=0.048). CONCLUSIONS: By utilizing chocolate balloon and sequential enlarging angioplasty, it becomes possible to use larger pre-dilation balloons and DCBs. In addition, the use of the chocolate balloon can significantly reduce the need for bailout stenting when compared with conventional balloons. CLINICAL IMPACT: The utilization of a chocolate balloon and sequential enlarging angioplasty has emerged as a promising technique for angioplasty procedures. This approach allows for the use of larger pre-dilation balloons and drug-coated balloons. The use of the chocolate balloon can significantly reduce the need for bail-out stenting when compared to conventional balloons. Further research is required to determine the impact of vessel preparation techniques on the primary patency.

Selective aneurysmal sac neck-targeted embolization during endovascular repair of abdominal aortic aneurysm with hostile neck anatomy.

PURPOSE: To evaluate the efficacy and safety of selective aneurysmal sac neck-targeted embolization in endovascular aneurysm repair (EVAR) in patients with a hostile neck anatomy (HNA). MATERIALS AND METHODS: Between October 2020 and June 2022, patients with an abdominal aortic aneurysm (AAA) and HNA who underwent EVAR with a low-profile stent graft and a selective aneurysmal sac neck-targeted embolization technique were analysed. An HNA was defined by the presence of any of the following parameters: infrarenal neck angulation > 60°; neck length < 15 mm; conical neck; circumferential calcification ≥ 50%; or thrombus ≥ 50%. Before occluding the entire aneurysm during the procedure, a buddy wire was loaded prophylactically into the sac through the contralateral limb side. If a type Ia endoleak (ELIa) occurred and persisted despite adjunctive treatment such as balloon moulding or cuff extension, this preloaded wire could be utilized to enable a catheter to reach the space between the stent graft and sac neck to perform coil embolization. In the absence of ELIa, the wire was simply retracted. The primary outcome of this study was freedom from sac expansion and endoleak-related reintervention during the follow-up period; secondary outcomes included technical success and intraoperative and in-hospital postoperative complications. RESULTS: Among the 28 patients with a hostile neck morphology, 11 (39.5%) who presented with ELIa underwent intraprocedural treatment involving sac neck-targeted detachable coil embolization. Seventeen individuals (60.7%) of the total patient population did not undergo coiling. All patients in the coiling group underwent balloon moulding, and 2 patients additionally underwent cuff extension. In the noncoiling group, 14 individuals underwent balloon moulding as a treatment for ELIa, while 3 patients did not exhibit ELIa during the procedure. The coiling group showed longer operating durations (81.27 ± 11.61 vs. 70.71 ± 7.17 min, P < 0.01) and greater contrast utilization than the noncoiling group (177.45 ± 52.41 vs. 108.24 ± 17.49 ml, P < 0.01). In the entire cohort, the technical success rate was 100%, and there were no procedure-related complications. At a mean follow-up of 18.6 ± 5.2 months (range 12-31), there were no cases of sac expansion (19 cases of sac regression, 67.86%; 9 cases of stability, 32.14%) or endoleak-related reintervention. CONCLUSIONS: Selective aneurysmal sac neck-targeted embolization for the treatment of ELIa in AAA patients with an HNA undergoing EVAR is safe and may prevent type Ia endoleak and related sac expansion after EVAR.

"Catheter Kissing" Technique to Recanalize Chronic Total Occlusions in Iliac Artery with Wire-Catheter Approach.

BACKGROUND: To describe a technique in which 2 5-F curved catheters were used to facilitate the wire-catheter approach for recanalizing chronic total occlusions (CTOs) in the iliac arteries concurrently affecting the common iliac artery and external iliac artery. METHODS: This was a single-center retrospective analysis involving endovascular recanalization of 17 iliac artery CTOs in 15 patients (mean age: 73.66 years; all men) between January 2019 and October 2022 using the subintimal arterial flossing with antegrade-retrograde intervention technique. With antegrade and retrograde guidewires in the subintimal spaces of CTOs, the location where the 2 guidewires seemed to overlap was identified as the rendezvous point. Although the 2 guidewires appeared to be in close proximity, there was no evidence that the bidirectional subintimal channels were connected. If several initial attempts failed, 2 5-F multipurpose catheters were introduced to the rendezvous point, followed by twisting, pulling, and pushing maneuvers until the tips of the catheters touched, indicating that the bidirectional subintimal channels were joined. A second wire rendezvous attempt was then employed to create a flossing-type guidewire. Outcome measurements included technical success, rendezvous points, complications, and procedure duration. RESULTS: Among this cohort, 80.0% smoked and 66.7% had hypertension. In 11 limbs (64.7%), when initial wire rendezvous attempts failed, the "catheter kissing" technique was employed to successfully recanalize iliac artery CTOs, taking an average of 3.80 ± 1.64 min to complete the secondary wire rendezvous. The average length of CTOs was 111.06 ± 9.99 mm, with 7 (41.2%) and 8 (47.1%) cases exhibiting severe calcification and flush occlusion, respectively. The wire rendezvous point for all cases was in external iliac artery and the average time for successful secondary wire rendezvous was 3.80 ± 1.64 min. All patients were treated with iliac artery stents. No statistically significant difference was observed between the puncture sites of the common femoral artery and superficial femoral artery in relation to failure of the primary wire rendezvous (P = 0.644). No in-hospital deaths or complications were associated with the procedure, including iliac artery rupture, distal embolization, or access site complications. CONCLUSIONS: In patients with extensive iliac artery CTOs, the "catheter kissing" technique may offer an effective and time-efficient recanalization approach, without requiring additional specialized devices. Importantly, the risk of complications remains unchanged even when employing a wire rendezvous in a challenging subintimal space.

Comparison of one-year outcomes and quality of life between endovenous microwave ablation and high ligation and stripping of the great saphenous vein.

INTRODUCTION: The objective of this study is to evaluate and compare the effectiveness of endovenous microwave ablation (EMA) and high ligation and strippingn (HLS) of the great saphenous vein (GSV) in the treatment of varicose veins. METHODS: We included 182 patients in each EMA and HLS groups. Follow-up outcomes included AVVQ, VCSS, chronic venous insufficiency questionnaire-14 (CIVIQ14) score, clinical recurrence rate of varicose vein treatment, and patient satisfaction during the 1-year follow-up period. RESULTS: At the 1-year follow-up, no significant difference was found in the clinical recurrence rate of varicose veins between the EMA and HLS groups (p = .75). The duration of the operation and the length of hospital stay for patients in the EMA group was shorter than that for the HLS group (p < .01). The Aberdeen Varicose Vein Questionnaire (AVVQ), Venous Clinical Severity Score (VCSS) score, and ecchymosis were lower for patients who underwent EMA surgery (p < .01). CONCLUSION: Our research results confirm that EMA improves patients' quality of life with lower limb varicose veins, with EMA showing higher patient satisfaction.

Corrigendum: Case Report: Iliac vein rupture during endovascular stenting in radiation-induced iliac venous stenosis.

[This corrects the article DOI: 10.3389/fonc.2023.1166812.].

Drug-Coated Balloon Angioplasty of Infrapopliteal Lesions in Chronic Limb-Threatening Ischemia: Six-month Outcomes of PRIME-WIFI.

PURPOSE: To evaluate 6-month outcomes of drug-coated balloon (DCB) angioplasty of infrapopliteal lesions in patients with chronic limb-threatening ischemia (CLTI). METHODS: We analyzed 6-month follow-up data from the 10-center PRIME-WIFI prospective registry on 300 consecutive patients (33.000% female) with CLTI who underwent DCB angioplasty for infrapopliteal arterial lesions. The primary outcome was freedom from major adverse event (MAE), a composite of major amputation, all-cause death, and clinically-driven target limb reintervention (CD-TLR). Secondary outcomes included amputation-free survival (AFS), freedom from each primary outcome component, primary sustained clinical improvement, and quality of life (QOL) score. Independent risk factors of MAE were determined using Cox proportional hazards regression analysis. RESULTS: A total of 409 infrapopliteal lesions in 312 limbs were treated with DCB, with 54.167% of the limbs being treated for isolated infrapopliteal lesions. By Kaplan-Meier analysis, at 6 months post- procedure (follow-up rate, 85.000%), freedom from MAE was 86.353%; AFS was 90.318%; and freedom from major amputation, all-cause death, and CD-TLR were 96.429%, 93.480%, and 95.079%, respectively. At 6-month follow-up, 83.590% of patients showed primary sustained clinical improvement, and QOL score (4.902±1.388) improved compared with that before procedure (2.327±1.109; p<0.001). Chronic renal insufficiency, chronic obstructive pulmonary disease, Rutherford grade, and postoperative infrapopliteal runoff score were independent risk factors for MAE within 6 months. CONCLUSION: In CLTI, DCB angioplasty of infrapopliteal lesions yields acceptable early efficacy and safety. CLINICAL IMPACT: This study evaluated the 6-month outcomes of DCB angioplasty in infrapopliteal lesions in CLTI patients by analyzing multicenter prospective data, showing that infrapopliteal DCB angioplasty can be performed with acceptable freedom from MAE rate, amputation-free survival rate, freedom from major amputation rate, survival rate, and freedom from CD-TLR rate. No patient experienced DCB-related intraoperative distal embolism. Chronic renal insufficiency, chronic obstructive pulmonary disease, Rutherford grade and postoperative infrapopliteal runoff score were independent risk factors for MAE within 6 months. Comparative real-world studies are needed.

Atrial septal defect occluder combined with stent graft for the management of post-dissection aortic aneurysm previously treated with unsuccessful coils: a case report.

BACKGROUND: Although the candy-plug technique has been reported to be useful for the treatment of post-dissection aortic aneurysm, the stent graft needs be to customized to accommodate the size of vascular occluders. CASE PRESENTATION: We present a case of a persistent false lumen successfully treated with endovascular stent-graft and atrial septal defect occluder in a patient with Stanford Type B dissection. A covered stent graft was implanted into the false cavity through a distal rupture, and an atrial septal defect occluder was inserted into the covered stent to seal of the false cavity. Decreased aneurysmal diameter and false lumen thrombosis were noted by CT scan at 6-month follow-up. CONCLUSIONS: Our case showed that combined use of a stent graft and atrial septal defect occluder is safe, technically feasible and effective in sealing of the false lumen in post-dissection aortic aneurysm patients with previously failed false lumen thrombosis.

Case report: Iliac vein rupture during endovascular stenting in radiation-induced iliac venous stenosis.

Only a few case reports in the medical literature describe radiation-induced iliac vein stenosis and endovascular therapy. We present a case of left external iliac vein stenosis resulting from radiotherapy for cervical cancer in which the iliac vein ruptured during the standard iliac vein stenting procedure. The emergency condition was resolved with the implantation of a covered stent and resuscitation with crystalloid and blood transfusion. The patient recovered without additional complications and was discharged eight days after endovascular therapy. At the six-month follow-up, the left lower limb edema had resolved completely, and the deep vein remained patent. This case might raise concerns regarding the potential risk of treating radiation-induced iliac venous stenosis, which may differ from that of a patient without a history of radiation therapy. Iliac vein rupture, iliac vein stenting, radiation-induced venous stenosis, case report.

Impact of age and tumor size on the development of the Kasabach-Merritt phenomenon in patients with kaposiform hemangioendothelioma: a retrospective cohort study.

Introduction: The Kasabach-Merritt phenomenon (KMP) is a severe complication of kaposiform hemangioendothelioma (KHE). The risk factors for KMP need further investigation. Methods: The medical records of patients with KHE were reviewed. Univariate and multivariate logistic regression models were used for the risk factors for KMP, and the area under the receiver operator characteristic (ROC) curve was used to assess the predictive power of risk factors. Results: A total of 338 patients with KHE were enrolled. The incidence of KMP was 45.9%. Age of onset (P < 0.001, odds ratio [OR] 0.939; 95% confidence interval [CI] 0.914-0.966), lesion size (P < 0.001, OR 1.944; 95% CI 1.646-2.296), mixed type (P = 0.030, OR 2.428; 95% CI 1.092-5.397), deep type (P = 0.010, OR 4.006; 95% CI 1.389-11.556), and mediastinal or retroperitoneal lesion location (P = 0.019, OR 11.864; 95% CI 1.497-94.003) were correlated with KMP occurrence through multivariate logistic regression. ROC curve analysis revealed that the optimal cutoffs were 4.75 months for the age of onset (P < 0.001, OR 7.206, 95% CI 4.073-12.749) and a lesion diameter of 5.35 cm (P < 0.001, OR 11.817, 95% CI 7.084-19.714). Bounded by a lesion size of 5.35 cm, we found significant differences in tumor morphology, age of onset, treatments, and hematological parameters. Using an onset age of 4.75 months as a cutoff, we found significant differences in tumor morphology, lesion size, hematological parameters, and prognosis. Conclusion: For KHE patients with an onset age <4.75 months and/or lesion diameter >5.35 cm, clinicians should be wary of the occurrence of KMP. Active management is recommended to improve the prognosis.

Cystic Adventitial Disease of the Common Femoral Vein Presenting with Lower Limb Swelling: A Case Report.

Cystic adventitial disease (CAD) is a rare vascular disorder predominantly seen in adults without cardiovascular risk factors. We report a case of CAD involving the common femoral vein in a 38-year-old female presented with right lower extremity swelling that was initially misdiagnosed as deep vein thrombosis (DVT). A computed tomography revealed a cystic structure that compressed the right common femoral vein with resultant severe stenosis of the vascular lumen. Complete evacuation of the cyst with excision of the cyst wall was performed, and the patient remained symptom-free at 3 year follow-up. This case highlighted that the rare venous CAD should be incorporated in the differential diagnosis of unilateral lower extremity swelling suspicious for a DVT. Complete evacuation and surgical excision of the cyst often conferred favorable clinical outcome.

A prospective, multicenter, real-world observational study evaluating the impact of tibial runoff on clinical outcomes after endovascular therapy for femoropopliteal lesions: Research protocol.

Introduction: Current evidence indicates endovascular intervention is a safe and effective treatment for peripheral artery disease of the lower extremity. However, the clinical outcome of endovascular intervention for femoropopliteal lesions has been shown to be affected by the status of tibial runoff. It remains unclear whether endovascular intervention for tibial runoff is associated with additional benefits. Methods and analysis: This prospective, multicenter, real-world observational study is carried out from January 2021 to December 2022 in 8 designated centers across China with an estimated sample size of 1200 patients with severe femoropopliteal disease. The pre-procedural status of tibial runoff is evaluated with the modified SVS score and categorized as good (SVS <5), compromised (SVS 5-10) or poor (SVS >10). Whether the patient will be treated with endovascular intervention for tibial runoff is determined by the treating vascular surgeons. Patients are dichotomized into the intervention group and the non-intervention group, with each group further divided into the good, compromised and poor tibial run-off subgroup, yielding 6 subgroups in total. Patients within various subgroups are compared with regard to the primary patency rate of the femoropopliteal artery, changes in quality of life, changes of Rutherford category, improvement of the Wound, Ischemia, and Foot Infection Classification, and incidence of major adverse events over 24-months follow-up. The results of this study may provide important information to help vascular sspecialists to decide whether the tibial runoff should be endovascularly intervened and which patient population benefits most from tibial runoff intervention. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT04675632?id=NCT04675632&draw=2&rank=1, NCT04675632.

Protocol of the evolution study: A prospective, multicenter, observational study evaluating the effect and health economics of endovascular treatment in patients with moderate and severe calcification of femoropopliteal artery.

Objectives: Peripheral artery disease with calcification is extremely prevalent in the elderly. Due to the calcification, it requires a different clinical approach than the more common arteriosclerosis obliterans of the lower extremity. The introduction of novel technologies such as the drug-coated balloon, directional atherectomy, supera and drug-eluting stent has improved the prognosis of these patients. This study will contribute to the development of higher-quality evidence-based medicine for clinical treatment by assessing the quality of life (QOL), clinical treatment effect, and health economics of patients with calcification. Method and analysis: The Evolution study is designed as a prospective, multicenter, observational, real-world study. From January 2021 to December 2022, 600 patients with moderate to severe femoropopliteal artery calcification will be recruited from ten locations in China. After discharge, information on demographics, disease history, procedure details, imaging findings, and follow-up will be collected. Patients will undergo follow-up at 1, 6, 12, 18, and 24 months after operation. Technical success rate, vascular quality of life questionnaire, primary patency rate of the target lesion, clinically driven target lesion revascularization rate (CD-TLR), and health economics evaluation are all included as outcome measures. Conclusions: The Evolution study helps to investigate the clinical and financial results of various endovascular therapy modalities for patients with moderate and severe femoropopliteal artery calcification. These actual facts may help to harmonize therapy recommendations for peripheral artery disease. Clinical trial registration: The study protocol was registered at www.clinicaltrials.gov (registration number: NCT04716361).

Treatment of Type I Endoleak after Thoracic Endovascular Aortic Repair and Stent Extension via False Lumen Catheterization and Coil Embolization.

Thoracic endovascular aortic repair (TEVAR) is a minimally invasive alternative to conventional open surgical reconstruction for the treatment of thoracic aortic dissection. However, the possibility of a type I endoleak may contribute to false lumen enlargement and rupture. Here, we present a case of successful treatment of type I endoleak after TEVAR and endograft extension for a complicated descending thoracic aortic dissection that was embolized by coils via a false lumen channel through the distal entry tear. This endovascular technology might offer a new option to treat thoracic type I endoleak by embolizing the blood entry site of the endoleak through the distal entry site and false lumen.

Endovascular Treatment of Thoracoabdominal Aorta Aneurysm by the Combination of a Stent Graft with Multiple Overlapping Bare Stents.

A 41-year-old male diagnosed with Crawford III thoracoabdominal aorta aneurysm (TAAA) was treated using a completely endovascular approach. After the combined implementation of 4 overlapping bare stents and a stent graft, TAAA was excluded while the 4 visceral arteries were reserved. Follow-up computed tomography scans at 3 and 6 months showed that the aneurysm had almost disappeared, while the vital branches remained open. This case may provide an acceptable alternative choice for treating TAAA in selected patients.

Alloreactive T cell responses and acute rejection of single class II MHC-disparate heart allografts are under strict regulation by CD4+ CD25+ T cells.

Skin but not vascularized cardiac allografts from B6.H-2bm12 mice are acutely rejected by C57BL/6 recipients in response to the single class II MHC disparity. The underlying mechanisms preventing acute rejection of B6.H-2bm12 heart allografts by C57BL/6 recipients were investigated. B6.H-2bm12 heart allografts induced low levels of alloreactive effector T cell priming in C57BL/6 recipients, and this priming was accompanied by low-level cellular infiltration into the allograft that quickly resolved. Recipients with long-term-surviving heart allografts were unable to reject B6.H-2bm12 skin allografts, suggesting potential down-regulatory mechanisms induced by the cardiac allografts. Depletion of CD25+ cells from C57BL/6 recipients resulted in 15-fold increases in alloreactive T cell priming and in acute rejection of B6.H-2bm12 heart grafts. Similarly, reconstitution of B6.Rag(-/-) recipients with wild-type C57BL/6 splenocytes resulted in acute rejection of B6.H-2bm12 heart grafts only if CD25+ cells were depleted. These results indicate that acute rejection of single class II MHC-disparate B6.H-2bm12 heart allografts by C57BL/6 recipients is inhibited by the emergence of CD25+ regulatory cells that restrict the clonal expansion of alloreactive T cells.

CD8 T cells can reject major histocompatibility complex class I-deficient skin allografts.

Following transplantation, recipient T cells can recognize and respond to donor antigens expressed directly on donor cells, and can respond to donor-derived peptides that have been processed and presented in the context of recipient MHC through the indirect pathway. Indirectly primed CD4(+) T cells have been well studied in transplantation, but little information is available regarding whether indirectly primed CD8(+) T cells participate in rejection. To address this, we placed MHC class I-deficient D(b)K(b) knockout skin grafts onto allogeneic H-2 (k) SCID recipients followed by adoptive transfer of purified H-2 (k) CD8(+) T cells. The MHC class I-deficient grafts were rejected and only CD8(+) T cells were detectable in the recipient lymphoid organs and in the skin grafts. Immunohistochemical analysis showed that CD8(+) T cells were found in close proximity to vascular endothelial cells and to recipient infiltrating macrophages, suggesting specific interactions. The data demonstrate that cross-primed polyclonal CD8(+) T cells can function as active participants in the effector phase of rejection. The findings confirm and extend previous studies using a monoclonal TCR transgenic T cell and shed light on mechanisms of acute and chronic graft injury that are potentially relevant to human transplant recipients.

Effects of T cell frequency and graft size on transplant outcome in mice.

The features that determine whether graft-reactive T lymphocytes develop into effector cells capable of mediating organ destruction are not well understood. To investigate potential factors involved in this process, we first confirmed that female recipient mice acutely rejected minor Ag-disparate male skin, but not heart transplants. Despite this difference in outcome, heart and skin transplantation induced antidonor T cell responses of similar magnitude, specificity, and cytokine profile. The heart-graft-primed T cells transiently infiltrated the graft and ultimately induced the development of chronic transplant vasculopathy. Increasing the frequency of donor-reactive T cells by presensitization or by using TCR (CD8+ antimale)-transgenic recipients did not mediate acute rejection but accelerated the pace and severity of the vasculopathy. Surprisingly, decreasing the tissue mass of the donor heart by 50% resulted in acute rejection of these smaller grafts without increasing the frequency of antidonor effector T cells in the recipients. In complementary studies, placement of one or two male skin grafts on a single recipient did not affect the frequency or cytokine profile of the induced antimale T cell repertoire. Nonetheless, the recipients of single grafts acutely rejected the transplanted skin while the recipients of two skin grafts did not. These results provide new insight into the pathogenesis of transplant vasculopathy and provide an explanation for the difference in outcome between murine skin and heart transplants by highlighting the novel concept that the efficiency of transplant-reactive T cell immunity is heavily influenced by the tissue burden it encounters at the effector stage.