Matthew G. Gipson

Epitope Mapping Using the X-Ray Crystallographic Structure of Complement Receptor Type 2 (CR2)/CD21: Identification of a Highly Inhibitory Monoclonal Antibody That Directly Recognizes the CR2-C3d Interface

Complement receptor type 2 (CR2)/CD21 is a B lymphocyte cell membrane C3d/iC3b receptor that plays a central role in the immune response. Human CR2 is also the receptor for the EBV viral membrane glycoprotein gp350/220. Both C3d and gp350/220 bind CR2 within the first two of 15–16 repetitive domains that have been designated short consensus/complement repeats. Many mAbs react with human CR2; however, only one currently available mAb is known to block both C3d/iC3b and gp350/220 binding. We have used a recombinant form of human CR2 containing the short consensus/complement repeat 1-2 ligand-binding fragment to immunize Cr2−/− mice. Following fusion, we identified and further characterized four new anti-CR2 mAbs that recognize this fragment. Three of these inhibited binding of CR2 to C3d and gp350/220 in different forms. We have determined the relative inhibitory ability of the four mAbs to block ligand binding, and we have used overlapping peptide-based approaches to identify linear epitopes recognized by the inhibitory mAbs. Placement of these epitopes on the recently solved crystal structure of the CR2-C3d complex reveals that each inhibitory mAb recognizes a site either within or adjacent to the CR2-C3d contact site. One new mAb, designated 171, blocks CR2 receptor-ligand interactions with the greatest efficiency and recognizes a portion of the C3d contact site on CR2. Thus, we have created an anti-human CR2 mAb that blocks the C3d ligand by direct contact with its interaction site, and we have provided confirmatory evidence that the C3d binding site seen in its crystal structure exists in solution.

Metaanalysis of survival, complications, and imaging response following chemotherapy-based transarterial therapy in patients with unresectable intrahepatic cholangiocarcinoma.

PURPOSE Unresectable intrahepatic cholangiocarcinoma represents a devastating illness with poor outcomes when treated with standard systemic therapies. Several smaller nonrandomized outcomes studies have been reported for such patients undergoing transarterial therapies. A metaanalysis was performed to assess primary clinical and imaging outcomes, as well as complication rates, following transarterial interventions in this patient population. MATERIALS AND METHODS By using standard search techniques and metaanalysis methodology, published reports (published in 2012 and before) evaluating survival, complications, and imaging response following transarterial treatments for patients with unresectable intrahepatic cholangiocarcinoma were identified and evaluated. RESULTS A total of 16 articles (N = 542 subjects) met the inclusion criteria and are included. Overall survival times were 15.7 months ± 5.8 and 13.4 months ± 6.7 from the time of diagnosis and time of first treatment, respectively. The overall weighted 1-year survival rate was 58.0% ± 14.5. More than three fourths of all subjects (76.8%) exhibited a response or stable disease on postprocedure imaging; 18.9% of all subjects experienced severe toxicities (National Cancer Institute/World Health Organization grade ≥ 3), and most experienced some form of postembolization syndrome. Overall 30-day mortality rate was 0.7%. CONCLUSIONS As demonstrated by this metaanalysis, transarterial chemotherapy-based treatments for cholangiocarcinoma appears to confer a survival benefit of 2-7 months compared with systemic therapies, demonstrate a favorable response by imaging criteria, and have an acceptable postprocedural complication profile. Such therapies should be strongly considered in the treatment of patients with this devastating illness.

Expression of human complement receptor type 2 (CD21) in mice during early B cell development results in a reduction in mature B cells and hypogammaglobulinemia.

Complement receptor (CR) type 2 (CR2/CD21) is normally expressed only during the immature and mature stages of B cell development. In association with CD19, CR2 plays an important role in enhancing mature B cell responses to foreign Ag. We used a murine Vλ2 promoter/Vλ2–4 enhancer minigene to develop transgenic mice that initiate expression of human CR2 (hCR2) during the CD43+CD25− late pro-B cell stage of development. We found peripheral blood B cell numbers reduced by 60% in mice expressing high levels of hCR2 and by 15% in mice with intermediate receptor expression. Splenic B cell populations were altered with an expansion of marginal zone cells, and basal serum IgG levels as well as T-dependent immune responses were also significantly decreased in transgenic mice. Mice expressing the highest levels of hCR2 demonstrated in the bone marrow a slight increase in B220intCD43+CD25− B cells in association with a substantial decrease in immature and mature B cells, indicative of a developmental block in the pro-B cell stage. These data demonstrate that stage-specific expression of CR2 is necessary for normal B cell development, as premature receptor expression substantially alters this process. Alterations in B cell development are most likely due to engagement of pre-B cell receptor-mediated or other regulatory pathways by hCR2 in a CD19- and possibly C3 ligand-dependent manner.

Endovascular Therapies for Primary Postpartum Hemorrhage: Techniques and Outcomes

Interventional radiologists are often consulted for acute management of hemorrhagic complications in obstetric and gynecologic patients. The aim of this article is to review the common indications for vascular embolization in obstetric and gynecologic emergencies, specifically in the setting of primary postpartum hemorrhage, and to discuss the technique and outcomes of endovascular treatment.

Intravascular US–Guided Portal Vein Access: Improved Procedural Metrics during TIPS Creation

PURPOSE To evaluate transjugular intrahepatic portosystemic shunt (TIPS) outcomes and procedure metrics with the use of three different image guidance techniques for portal vein (PV) access during TIPS creation. MATERIALS AND METHODS A retrospective review of consecutive patients who underwent TIPS procedures for a range of indications during a 28-month study period identified a population of 68 patients. This was stratified by PV access techniques: fluoroscopic guidance with or without portography (n = 26), PV marker wire guidance (n = 18), or intravascular ultrasound (US) guidance (n = 24). Procedural outcomes and procedural metrics, including radiation exposure, contrast agent volume used, procedure duration, and PV access time, were analyzed. RESULTS No differences in demographic or procedural characteristics were found among the three groups. Technical success, technical success of the primary planned approach, hemodynamic success, portosystemic gradient, and procedure-related complications were not significantly different among groups. Fluoroscopy time (P = .003), air kerma (P = .01), contrast agent volume (P = .003), and total procedural time (P = .02) were reduced with intravascular US guidance compared with fluoroscopic guidance. Fluoroscopy time (P = .01) and contrast agent volume (P = .02) were reduced with intravascular US guidance compared with marker wire guidance. CONCLUSIONS Intravascular US guidance of PV access during TIPS creation not only facilitates successful TIPS creation in patients with challenging anatomy, as suggested by previous investigations, but also reduces important procedure metrics including radiation exposure, contrast agent volume, and overall procedure duration compared with fluoroscopically guided TIPS creation.

ACR Appropriateness Criteria Radiologic Management of Hepatic Malignancy

Management of hepatic malignancy is a challenging clinical problem involving several different medical and surgical disciplines. Because of the wide variety of potential therapies, treatment protocols for various malignancies continue to evolve. Consequently, development of appropriate therapeutic algorithms necessitates consideration of medical options, such as systemic chemotherapy; surgical options, such as resection or transplantation; and locoregional therapies, such as thermal ablation and transarterial embolization. The authors discuss treatment strategies for the 3 most common subtypes of hepatic malignancy treated with locoregional therapies: hepatocellular carcinoma, neuroendocrine metastases, and colorectal metastases. The ACR Appropriateness Criteria(®) are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

ACR Appropriateness Criteria Radiologic Management of Infected Fluid Collections

The best management of infected fluid collections depends on a careful assessment of clinical and anatomic factors as well as an up-to-date review of the published literature, to be able to select from a host of multidisciplinary treatment options. This article reviews conservative, radiologic, endoscopic, and surgical options and their best application to infected fluid collections as determined by the ACR Appropriateness Criteria Expert Panel on Interventional Radiology. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals, and the application, by the panel, of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Pelvic Vascular Malformations

Vascular malformations (VMs) comprise a wide spectrum of lesions that are classified by content and flow characteristics. These lesions, occurring in both focal and diffuse forms, can involve any organ and tissue plane and can cause significant morbidity in both children and adults. Since treatment strategy depends on the type of malformation, correct diagnosis and classification of a vascular lesion are crucial. Slow-flow VMs (venous and lymphatic malformations) are often treated by sclerotherapy, whereas fast-flow lesions (arteriovenous malformations) are generally managed with embolization. In addition, some cases of VMs are best treated surgically. This review will present an overview of VMs in the female pelvis as well as a discussion of endovascular therapeutic techniques.

Percutaneous Management of Lymphoceles after Renal Transplantation

Chronic kidney disease (CKD) is a worldwide public health problem. In the United States, between 1988-1994 and 2005-2010, the overall prevalence estimate for CKD, defined by an estimation of glomerular filtration rate <60 ml/min per 1.73m2 or a urine albumin-to-creatinine ratio ≥30 mg/g, rose from 12.3 to 14.0%. In 2010, overall per person per year costs for patients with CKD reached

ACR Appropriateness Criteria ® Radiologic Management of Uterine Leiomyomas

22,323 for Medicare patients ≥65 years and older, and the overall Medicare expenditure for CKD was