Mechanotransduction via endothelial adhesion molecule CD31 initiates transmigration and reveals a role for VEGFR2 in diapedesis.

Engagement of platelet endothelial cell adhesion molecule 1 (PECAM, PECAM-1, CD31) on the leukocyte pseudopod with PECAM at the endothelial cell border initiates transendothelial migration (TEM, diapedesis). We show, using fluorescence lifetime imaging microscopy (FLIM), that physical traction on endothelial PECAM during TEM initiated the endothelial signaling pathway. In this role, endothelial PECAM acted as part of a mechanotransduction complex with VE-cadherin and vascular endothelial growth factor receptor 2 (VEGFR2), and this predicted that VEGFR2 was required for efficient TEM. We show that TEM required both VEGFR2 and the ability of its Y1175 to be phosphorylated, but not VEGF or VEGFR2 endogenous kinase activity. Using inducible endothelial-specific VEGFR2-deficient mice, we show in three mouse models of inflammation that the absence of endothelial VEGFR2 significantly (by ≥75%) reduced neutrophil extravasation by selectively blocking diapedesis. These findings provide a more complete understanding of the process of transmigration and identify several potential anti-inflammatory targets.

Myocardial strain is associated with adverse cardiac events in patients treated with chimeric antigen receptor (CAR) T-cell therapy.

BACKGROUND: Cardiovascular events, including heart failure and arrhythmias, following chimeric antigen receptor (CAR) T-cell therapy are increasingly recognized. Although global longitudinal strain (GLS) has demonstrated prognostic utility for other cancer therapy-related cardiac dysfunction, less is known regarding the association of GLS with adverse cardiac events following CAR T-cell therapy. OBJECTIVES: To determine the association of baseline GLS with adverse cardiovascular events in adults receiving CAR-T cell therapy. METHODS: Patients who had an echocardiogram within 6 months prior to receiving CAR T-cell therapy were retrospectively identified. Clinical data and cardiac events were collected via chart review. Echocardiograms were analyzed offline for GLS, left ventricular ejection fraction, and Doppler parameters. Multivariable logistic regression was used to determine the association between adverse cardiovascular events and echocardiographic parameters. RESULTS: Among 75 CAR T-cell therapy patients (mean age 63.9, 34.7% female), nine patients (12%) experienced cardiac events (CEs) including cardiovascular death, new/worsening heart failure, and new/worsening arrhythmia within 1 year of treatment. In univariable models, higher baseline GLS (OR 0.78 [0.63, 0.96], p = .021) was associated with a lower risk of CE and higher baseline mitral E/e' (OR 1.40 [1.08, 1.81], p = .012) was associated with a higher risk of CE. After adjusting for age and LDH, higher baseline GLS (OR 0.65 [0.48-0.88], p = <.01) was associated with a lower risk of CE and higher baseline mitral E/e' (OR 1.56 [1.06, 2.29], p = .024) was associated with a higher risk of CE. CONCLUSION: Lower GLS and higher mitral E/e' on a baseline echocardiogram were associated with higher risk for CEs in patients receiving CAR T-cell therapy.

Endothelial Cell Calcium Signaling during Barrier Function and Inflammation.

Calcium is an essential second messenger in endothelial cells and plays a pivotal role in regulating a number of physiologic processes, including cell migration, angiogenesis, barrier function, and inflammation. An increase in intracellular Ca2+ concentration can trigger a number of diverse signaling pathways under both physiologic and pathologic conditions. In this review, we discuss how calcium signaling pathways in endothelial cells play an essential role in affecting barrier function and facilitating inflammation. Inflammatory mediators, such as thrombin and histamine, increase intracellular calcium levels. This calcium influx causes adherens junction disassembly and cytoskeletal rearrangements to facilitate endothelial cell retraction and increased permeability. During inflammation endothelial cell calcium entry and the calcium-related signaling events also help facilitate several leukocyte-endothelial cell interactions, such as leukocyte rolling, adhesion, and ultimately transendothelial migration.

Intercellular Adhesion Molecule 1 Functions as an Efferocytosis Receptor in Inflammatory Macrophages.

Intercellular adhesion molecule-1 (ICAM-1) is up-regulated during inflammation by several cell types. ICAM-1 is best known for its role in mediating leukocyte adhesion to endothelial cells and guiding leukocytes across the vascular wall. Recently, macrophages have been shown to express ICAM-1, however, their role in macrophage function is unclear. We found that ICAM-1 expression was induced during inflammatory macrophage polarization and high numbers of ICAM-1-expressing macrophages were noted in inflamed colon tissue in a murine colitis model and in human inflammatory bowel disease. Because tissue macrophages play a critical role in removing apoptotic/necrotic cells in inflammation and injury, a process termed efferocytosis, it was examined whether ICAM-1 contributes to this process. Genetic deletion (ICAM-1 knockout mice) or siRNA-mediated knockdown of ICAM-1 in isolated murine and human macrophages significantly impaired apoptotic cell (AC) engulfment. Impairment in the engulfment of Jurkat T cells, neutrophils, and epithelial cells was confirmed ex vivo by inflammatory macrophages and in vivo by thioglycolate-recruited peritoneal macrophages. Decreased efferocytosis was also seen in vitro and in vivo with inhibition of ICAM-1 adhesive interactions, using a function blocking anti-ICAM-1 antibody. Mechanistically, it was found that ICAM-1 actively redistributes to cluster around engulfed ACs to facilitate macrophage-AC binding. Our findings define a new role for ICAM-1 in promoting macrophage efferocytosis, a critical process in the resolution of inflammation and restoration of tissue homeostasis.

REVIEW OF OPHTHALMIC AND BREASTFEEDING MEDICINE EVIDENCE: Real and Theoretical Risks of Intravitreal Anti-Vascular Endothelial Growth Factor Administration in Lactating Women.

BACKGROUND/PURPOSE: There is limited research regarding the consequences of treating lactating mothers with intravitreal anti-vascular endothelial growth factor (VEGF) agents. Balancing the need for vision-saving treatment, the benefits of breastfeeding, and the concern for affecting the newborn can present a conflict for both mothers and ophthalmologists. This review summarizes the state of the literature regarding the use of intravitreal anti-VEGF agents during breastfeeding along with details about their pharmacology. RESULTS: Bevacizumab and aflibercept have Fc domains subjecting them to FcRn recycling and extending their half-life compared with ranibizumab which is an antibody fragment and lacks the Fc domain. Case reports and small studies have shown that ranibizumab has the lowest serum concentration after intravitreal injection and the least effect on plasma-free VEGF concentrations and breastmilk VEGF levels. CONCLUSION: Clinical and pharmacologic data suggest that ranibizumab has less systemic circulation and effect on maternal serum and breastmilk VEGF levels when compared to bevacizumab and aflibercept. However, there is significant need for further research on the degree and duration to which intravitreal agents circulate systemically, what fraction is transferred into breastmilk and is absorbed, and whether this results in any functional adverse effects to the infant. Other factors to consider in the medical decision-making of lactating mothers necessitating intravitreal anti-VEGF treatment include the gestational and post-natal age of the child and whether it is feasible to avoid breastfeeding for the half-life duration of the intravitreal agent rather than ceasing breastfeeding altogether.

Gross total resection and adjuvant radiotherapy most significant predictors of improved survival in patients with atypical meningioma.

BACKGROUND: Atypical and malignant meningiomas are far less common than benign meningiomas. As aggressive lesions, they are prone to local recurrence and may lead to decreased survival. Although malignant meningiomas typically are treated with maximal surgical resection and adjuvant radiotherapy (RT), to the authors' knowledge the optimal treatment for atypical lesions remains to be defined. There are limited prospective data in this setting. METHODS: The National Cancer Data Base was queried to investigate cases of histologically confirmed meningiomas diagnosed from 2004 to 2014. This included 7811 patients with atypical meningiomas (World Health Organization grade 2) and 1936 patients with malignant meningiomas (World Health Organization grade 3); during the same period, a total of 60,345 patients were diagnosed with benign meningiomas (World Health Organization grade 1). Data collected included patient and tumor characteristics, extent of surgical resection, and use of RT. Survival analysis was performed using Kaplan-Meier estimates with the log-rank test of significance and Cox univariate and multivariate regression. Logistic regression was used to determine factors associated with use of RT. RESULTS: The 5-year overall survival rate was 85.5% in patients with benign meningiomas, 75.9% in patients with atypical meningiomas, and 55.4% in patients with malignant meningiomas (P<.0001). In patients with atypical meningiomas, gross (macroscopic) total resection (GTR) and adjuvant RT were found to be associated with significantly improved survival, independently and especially in unison (GTR plus RT: hazard ratio, 0.47; P = .002). On multivariate analysis, the combination of GTR plus RT was found to be the most important factor for improved survival. However, GTR was associated with significantly lower rates of RT use. CONCLUSIONS: GTR and adjuvant RT appear to be highly associated with improved survival, independent of other factors, in patients with atypical meningiomas. Cancer 2018;124:734-42. © 2017 American Cancer Society.

Heart Failure Risk Among African-American Women With an ICAM1 Missense Variant.

BACKGROUND: A common genetic variant of ICAM1 among African-American individuals (rs5491; p.K56M) is associated with heart failure (HF) hospitalization, but whether this risk is specific to heart failure with preserved ejection fraction (HFpEF) remains unclear. Older women are at high risk for HFpEF, and the relationship between rs5491 and HFpEF across the age spectrum is unknown. OBJECTIVES: This study assessed risk of HF and its subtypes conferred by ICAM1 p.K56M (rs5491). METHODS: Associations of rs5491 with risk of HF and its subtypes were estimated among African American individuals in WHI (Women's Health Initiative). The study evaluated whether the association between rs5491 and HF hospitalizations was modified by baseline age. Subsequently, African-American women in WHI and MESA (Multi-Ethnic Study of Atherosclerosis) were pooled and analyses were repeated. RESULTS: Among 8,401 women in WHI, the minor allele frequency of rs5491 was 20.7%, and 731 HF hospitalizations occurred over 19.2 years. The rs5491 variant was not associated with HF or its subtypes across WHI. Interaction analyses suggested that age as a continuous variable modified the association of rs5491 with HFpEF hospitalization (interaction P = 0.04). Upon categorizing women into age decades, rs5491 conferred increased risk of HFpEF among women ≥70 years (HR per additional rs5491 allele: 1.82 [95% CI: 1.25-2.65]; P = 0.002) but was not associated with HFpEF risk among women <70 years. Pooling African-American women in WHI (n = 8,401) and MESA (n = 856) demonstrated that the effect modification by age on the association of rs5491 with HFpEF became more significant (interaction P = 0.009), with consistent HFpEF risk effect estimates among women ≥70 years. CONCLUSIONS: ICAM1 p.K56M (rs5491) is associated with HFpEF among African-American women ≥70 years.

Proteomic Profile of the ICAM1 p.K56M HFpEF Risk Variant.

A common missense variant in ICAM1 among African American individuals (rs5491; pK56M) has been associated with risk of heart failure with preserved ejection fraction (HFpEF), but the pathways that lead to HFpEF among those with this variant are not clear. In this analysis of 92 circulating proteins and their associated networks, we identified 7 circulating inflammatory proteins associated with rs5491 among >600 African American individuals. Using weighted coexpression network analysis, 3 protein networks were identified, one of which was associated with rs5491. This protein network was most highly represented by members of the tumor necrosis receptor superfamily. The rs5491 variant demonstrated an inflammatory proteomic profile in a separate cohort of African American individuals. This analysis identifies inflammatory pathways that may drive HFpEF among African American individuals with the ICAM1 pK56M (rs5491) variant.

The Association of Intravitreal Anti-VEGF Injections With Kidney Function in Diabetic Retinopathy.

Purpose: To examine whether patients with diabetic retinopathy receiving intravitreal anti-VEGF injections are at increased risk of kidney function decline. Design: Retrospective cohort study. Participants: Included 187 patients who received intravitreal anti-VEGF injections for proliferative diabetic retinopathy (PDR) and/or diabetic macular edema (DME), and 929 controls with non-PDR who did not receive injections, at a large tertiary care center in Chicago, Illinois. Methods: We queried our institutional enterprise data warehouse to identify patients with diabetic retinopathy, determined whether they received intravitreal anti-VEGF injections, and followed kidney function for all patients over time. Main Outcome Measures: We assessed time to sustained 40% decline in estimated glomerular filtration rate (eGFR) from baseline in patients receiving intravitreal anti-VEGF injections and compared it with controls using Kaplan-Meier and multivariable adjusted Cox proportional hazards regression models. Results: This study included 1116 patients (565 female [50.6%]; mean [standard deviation {SD}] age, 57.3 [13.6] years; mean [SD] eGFR, 65.3 [32.1] ml/min/1.73 m2). Of these, 187 patients received ≥ 1 intravitreal anti-VEGF injection (mean [SD], 11.4 [13.1] injections) for PDR and/or DME, and 929 controls with non-PDR received no injections. Intravitreal anti-VEGF injection use was not associated with an increased risk of kidney function decline (hazard ratio [HR], 1.44; 95% confidence interval [CI], 0.97-2.15). Subgroup analyses revealed that use of intravitreal anti-VEGF injections was associated with increased risk of kidney function decline in male patients (HR, 1.87; 95% CI, 1.11-3.14) but not female patients (HR, 0.97; 95% CI, 0.50-1.89). Intravitreal anti-VEGF injection use was also associated with an increased risk of kidney function decline in patients with baseline eGFR > 30 ml/min/1.73 m2 (HR, 1.86; 95% CI, 1.15-3.01), but not in individuals with baseline eGFR ≤ 30 ml/min/1.73 m2 (HR, 0.97; 95% CI, 0.45-2.10). Among patients who received injections, receiving ≥ 12 injections was not associated with risk of kidney function decline (HR, 1.13; 95% CI, 0.52-2.49). Conclusions: Intravitreal anti-VEGF injections for patients with diabetic retinopathy are overall well-tolerated with respect to kidney function, but the use of intravitreal anti-VEGF injections was associated with an increased risk of kidney function decline in certain subgroups of patients. Financial Disclosures: Proprietary or commercial disclosure may be found after the references.

Single-cell profiling reveals inflammatory polarization of human carotid versus femoral plaque leukocytes.

Femoral atherosclerotic plaques are less inflammatory than carotid plaques histologically, but limited cell-level data exist regarding comparative immune landscapes and polarization at these sites. We investigated intraplaque leukocyte phenotypes and transcriptional polarization in 49 patients undergoing femoral (n = 23) or carotid (n = 26) endarterectomy using single-cell RNA-Seq (scRNA-Seq; n = 13), flow cytometry (n = 24), and IHC (n = 12). Comparative scRNA-Seq of CD45+-selected leukocytes from femoral (n = 9; 35,265 cells) and carotid (n = 4; 30,655 cells) plaque revealed distinct transcriptional profiles. Inflammatory foam cell-like macrophages and monocytes comprised higher proportions of myeloid cells in carotid plaques, whereas noninflammatory foam cell-like macrophages and LYVE1-overexpressing macrophages comprised higher proportions of myeloid cells in femoral plaque (P < 0.001 for all). A significant comparative excess of CCR2+ macrophages in carotid versus plaque was observed by flow cytometry in a separate validation cohort. B cells were more prevalent and exhibited a comparatively antiinflammatory profile in femoral plaque, whereas cytotoxic CD8+ T cells were more prevalent in carotid plaque. In conclusion, human femoral plaques exhibit distinct macrophage phenotypic and transcriptional profiles as well as diminished CD8+ T cell populations compared with human carotid plaques.

Adverse Cardiac Effects of CAR T-Cell Therapy: Characteristics, Surveillance, Management, and Future Research Directions.

This review summarizes the current literature on the adverse cardiac effects of CAR T-cell therapy. Case reports and series suggest that major adverse cardiovascular events are not uncommon after CAR T-cell therapy; however, limited data exist regarding incidence, pathophysiology, and prevention strategies related to CAR T-associated cardiovascular events. As cellular therapy advances and the indications for its use continue to expand, it is essential to better understand its associated cardiovascular toxicities. Biomarkers, cardiac imaging, longitudinal data from larger populations, and translational research are all essential areas for further research. Interestingly, CAR T-cell therapy can also be used to reverse cardiac fibrosis in murine models. Altogether this underscores the need to broadly understand how T-cells, endogenous and engineered, may impact cardiovascular diseases.

Hypocalcemia prevention and management after thyroidectomy in children: A systematic review.

INTRODUCTION: Hypocalcemia is the most common complication following thyroidectomy in children. Guidelines to manage post-thyroidectomy hypocalcemia are available for adults, but not children. The objective of this review was to identify practices related to hypocalcemia prevention and management in pediatric patients. METHODS: We identified studies examining the prevention and management of hypocalcemia in pediatric patients post-thyroidectomy within PubMed, EMBASE, Web of Science and Cochrane databases. Three independent reviewers screened citations and reviewed full-text papers. RESULTS: A total of 15 studies were included, representing 1552 patients. The overall study quality was weak with lack of randomization and inconsistent outcome reporting. The pooled incidence of hypocalcemia from the 15 studies was 35.5% for transient hypocalcemia and 4.2% for permanent hypocalcemia. All studies discussed post-operative hypocalcemia treatment, with most patients requiring admission for intra-venous calcium therapy. One study described a protocol discharging asymptomatic patients on calcitriol and calcium. Three studies discussed preoperative calcium supplementation in patients at risk of hypocalcemia. No studies examined routine use of calcium and/or vitamin D supplementation to prevent post-operative hypocalcemia. CONCLUSION: A significant number of children undergoing thyroidectomy develop hypocalcemia. Despite this high incidence, our systematic review demonstrates significant practice variation surrounding post-thyroidectomy hypocalcemia prevention and management in children. LEVEL OF EVIDENCE: III (systematic review of studies of which some were case-control studies (III) and some were case series (IV)).

Spatiotemporal restriction of endothelial cell calcium signaling is required during leukocyte transmigration.

Endothelial cell calcium flux is critical for leukocyte transendothelial migration (TEM), which in turn is essential for the inflammatory response. Intravital microscopy of endothelial cell calcium dynamics reveals that calcium increases locally and transiently around the transmigration pore during TEM. Endothelial calmodulin (CaM), a key calcium signaling protein, interacts with the IQ domain of IQGAP1, which is localized to endothelial junctions and is required for TEM. In the presence of calcium, CaM binds endothelial calcium/calmodulin kinase IIδ (CaMKIIδ). Disrupting the function of CaM or CaMKII with small-molecule inhibitors, expression of a CaMKII inhibitory peptide, or expression of dominant negative CaMKIIδ significantly reduces TEM by interfering with the delivery of the lateral border recycling compartment (LBRC) to the site of TEM. Endothelial CaMKII is also required for TEM in vivo as shown in two independent mouse models. These findings highlight novel roles for endothelial CaM and CaMKIIδ in transducing the spatiotemporally restricted calcium signaling required for TEM.

Risk factors for auricular hematoma and recurrence after drainage.

OBJECTIVES/HYPOTHESIS: To review an institutional experience with auricular hematoma across all clinical settings including the emergency department (ED) and outpatient clinics at an urban tertiary care academic hospital, characterize practice patterns across setting and specialty, and assess for factors predictive of treatment success. METHODS: Patients presenting to the ED, admitted to an inpatient ward, or seen in the outpatient setting between 2000 and 2017 with a diagnosis of auricular hematoma were reviewed. A number of relevant patient features including demographic factors, medications, and social risk factors were analyzed, as were several factors related to the presentation and management of the hematoma to identify variables of clinical significance. RESULTS: A total of 87 individual cases were identified. Auricular hematomas most commonly occurred in males after sports-related trauma (e.g., martial arts, wrestling, boxing). Factors associated with lower rates of recurrence included initial treatment by or in consultation with an otolaryngologist and application of a bolster dressing. CONCLUSIONS: In our cohort, initial management of auricular hematoma by an otolaryngologist or with an otolaryngology consultation and placement of a bolster dressing was associated with lower rates of hematoma recurrence. LEVEL OF EVIDENCE: 2b Laryngoscope, 130:628-631, 2020.

Development, Validation, and Interpretation of the PROMIS Itch Questionnaire: A Patient-Reported Outcome Measure for the Quality of Life Impact of Itch.

Current patient-reported outcome measures for itch are limited and may not capture its full impact on health-related quality of life. We sought to develop, calibrate, and validate banks of questions assessing the health-related quality of life impact of itch as part of the Patient-Reported Outcomes Measurement Information System. A systematic process of literature review, content-expert review, qualitative research, testing in a sample of 600 adults, classical test theory methods, and item response theory analyses were applied. Exploratory and confirmatory factor analyses were followed by item response theory model and item fit analyses. Four itch-related item banks were developed: (i) general concerns, (ii) mood and sleep, (iii) clothing and physical activity, and (iv) scratching behavior. Item response theory and expert content review narrowed the item banks to 25, 18, 15, and 5 items, respectively. Validity of the item banks was supported by good convergent and discriminant validity with itch intensity, internal consistency, and no significant floor or ceiling effects. In conclusion, the Patient-Reported Outcomes Measurement Information System Itch Questionnaire banks have excellent measurement properties and efficiently and comprehensively assess the burden of itch.

A novel treatment for skin repair using a combination of spironolactone and vitamin D3.

Injury of the skin from exposure to toxic chemicals leads to the release of inflammatory mediators and the recruitment of immune cells. Nitrogen mustard (NM) and other alkylating agents cause severe cutaneous damage for which there are limited treatment options. Here, we show that combined treatment of vitamin D3 (VD3) and spironolactone (SP), a mineralocorticoid receptor antagonist, significantly improves the resolution of inflammation and accelerates wound healing after NM exposure. SP enhanced the inhibitory effect of VD3 on nuclear factor-kB activity. Combined treatment of NM-exposed mice with VD3 and SP synergistically inhibited the expression of iNOS in the skin and decreased the expression of matrix metallopeptidase-9, C-C motif chemokine ligand 2, interleukin (IL)-1α, and IL-1ß. The combined treatment decreased the number of local proinflammatory M1 macrophages resulting in an increase in the M2/M1 ratio in the wound microenvironment. Apoptosis was also decreased in the skin after combined treatment. Together, this creates a proresolution state, resulting in more rapid wound closure. Combined VD3 and SP treatment is effective in modulating the immune response and activating anti-inflammatory pathways in macrophages to facilitate tissue repair. Altogether, these data demonstrate that VD3 and SP may constitute an effective treatment regimen to improve wound healing after NM or other skin chemical injury.

Prognostic Significance of Nuclear Factor Kappa B Expression in Locally Advanced Cervical Cancer Patients Treated Definitively With Concurrent Chemoradiation.

OBJECTIVES: Nuclear factor kappa B (NFkB) is a transcription factor shown to confer treatment resistance in tumors. A previous report suggested an association between pretreatment NFkB and poorer outcomes for cervical cancer patients treated with chemoradiation therapy (CRT). We aimed to validate their findings in a larger patient cohort. MATERIALS AND METHODS: This Institutional Review Board approved study included patients with locally advanced cervical cancer patients treated with CRT. Evaluation of both nuclear and cytoplasmic immunoreactivity for NFkB was scored semiquantitatively by 3 pathologists. Cytoplasmic positivity incorporated both the intensity and percentage of immunoreactivity in invasive carcinoma (H-score), whereas nuclear positivity was assessed by percentage of positive cells. Outcomes were stratified by NFkB overexpression and tumor characteristics. Overall survival (OS), progression-free survival (PFS), distant metastases-free survival (DMFS), and local regional control (LC) were obtained using Kaplan-Meier and differences between groups were evaluated by the log-rank test. Hazard ratios were obtained using Cox regression for both univariate and multivariate analyses. RESULTS: The mean age was 51 years old and most (78.57%) had locally advanced disease. Five-year OS, PFS, LC, and DMFS in the entire cohort were 57.18% (confidence interval [CI], 34.06%-74.82%), 48.07% (CI, 25.50%-67.52%), 72.11% (CI, 49.96%-85.73%), and 62.85% (CI, 36.33%-80.82%), respectively. There was no significant association between NFkB expression (H-index ≥180) and 3-year and 5-year OS (P-value=0.34), PFS (P-value=0.21), LC (P-value=0.86), or DMFS (P-value=0.18). CONCLUSIONS: Our study demonstrated that cytoplasmic NFkB-p65 expression (H-index ≥180) was associated with a nonstatistically significant trend toward poor clinical outcomes in locally advanced cervical cancer patients treated definitively with CRT.

Endothelial IQGAP1 regulates leukocyte transmigration by directing the LBRC to the site of diapedesis.

Transendothelial migration (TEM) of leukocytes across the endothelium is critical for inflammation. In the endothelium, TEM requires the coordination of membrane movements and cytoskeletal interactions, including, prominently, recruitment of the lateral border recycling compartment (LBRC). The scaffold protein IQGAP1 was recently identified in a screen for LBRC-interacting proteins. Knockdown of endothelial IQGAP1 disrupted the directed movement of the LBRC and substantially reduced leukocyte TEM. Expression of truncated IQGAP1 constructs demonstrated that the calponin homology domain is required for IQGAP1 localization to endothelial borders and that the IQ domain, on the same IQGAP1 polypeptide, is required for its function in TEM. This is the first reported function of IQGAP1 requiring two domains to be present on the same polypeptide. Additionally, we show for the first time that IQGAP1 in the endothelium is required for efficient TEM in vivo. These findings reveal a novel function for IQGAP1 and demonstrate that IQGAP1 in endothelial cells facilitates TEM by directing the LBRC to the site of TEM.