Prospective intraoperative syndesmotic evaluation during ankle fracture fixation: stress external rotation versus lateral fibular stress.

OBJECTIVES: We hypothesized that the method of stress external rotation more accurately reproduces the mechanism of injury, and therefore this diagnostic method more likely detects ankle instability than the fibular stress examination. DESIGN: Prospective cohort comparison study. SETTING: Level 1 trauma center. PATIENTS: Twenty-eight consecutive patients with unstable ankle fractures presenting within 7 days from the time of injury. Previous ankle surgical history or age younger than 18 years was excluded. INTERVENTION: Stress external rotation and lateral fibular stress examination was performed intraoperatively. MAIN OUTCOME MEASURE: Radiographic measurement of the tibiofibular clear space, tibiofibular overlap, and medial clear space were recorded. RESULTS: After normalization of the fluoroscopic measurements, there was no difference in detecting changes in tibiofibular clear space or tibiofibular overlap. However, there was a significant difference in detecting medial clear space widening with stress external rotation. Compared with lateral fibular stress, stress external rotation demonstrated a 35% increase (P < 0.05) in medial clear space widening. This difference correlates with the 1-2-mm difference of additional widening with stress external rotation. CONCLUSIONS: Untreated instability impacts patient outcomes. The difference in widening with stress external rotation was significantly greater than lateral fibular stress and appreciable on standard fluoroscopic views. Stress external rotation radiographs are a more reliable indicator of mortise instability than traditional lateral fibular stress. LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Substantial improvement in prophylactic antibiotic administration for open fracture patients: results of a performance improvement program.

OBJECTIVES: Administration of early and appropriate antibiotic in treating patients with open fractures is an important early factor in preventing infection and optimizing outcomes. The purpose of this study is to evaluate the effects of an orthopaedic trauma performance improvement program directed at early antibiotic administration for open fracture patients at our trauma center. DESIGN: Retrospective comparative cohort study of patients treated for an open fracture by before and after implementation of our performance improvement program specifically designed to address early open fracture care. SETTING: Single metropolitan level 2 regional trauma center. PATIENTS: Patients with open fractures treated by orthopaedic surgery (hand and spine excluded) at our institution between January 2012 and December 2013 were included. Patients transferred from another facility were excluded. INTERVENTION: Patients were divided into one of the following 2 groups. Group 1 included patients treated before our open fracture performance improvement program (January 2012-December 2012) and group 2 comprised those treated after the program was instituted (January 2013-December 2013). MAIN OUTCOME MEASUREMENTS: Patient demographics, injury factors, and performance measures relating to early open fracture care [eg, the characteristics of early antibiotic administration in their treatment course, including timeliness of prophylactic intravenous (IV) antibiotic therapy and reasons for delay or omission of these treatments] were evaluated. RESULTS: Group 1 was comprised of 127 patients with a total of 142 open fractures, whereas group 2 included 132 patients with a total of 156 open fractures. Patient and injury factors were not significantly different between the 2 groups. Group 1 received IV antibiotics at an average of 70.5 minutes after arrival at our institution compared with group 2 who received antibiotics at an average of 32.4 minutes (P < 0.001). The average times from emergency department arrival to physician evaluation improved from 6.5 to 4.5 minutes (P = 0.02) and antibiotic order to antibiotic delivery improved from 37 to 13 minutes (P < 0.001) for group 1 compared with group 2, respectively. The average time between physician evaluation and antibiotic showed a trend toward improvement (12.7-8.0 minutes, P = 0.57). Fifty percent of patients in group 1 (63/127) had antibiotics initiated within 1 hour of hospital arrival, whereas 78% (100/132) in group 2 had antibiotics initiated within 1 hour (P < 0.001). Eighty-five percent (112/127) of patients in group 1 had antibiotics initiated within 3 hours of hospital arrival, whereas 95% (125/132) in group 2 had antibiotics initiated within 3 hours (P = 0.03). Of those patients receiving standard antibiotics (cephalosporin), 79% (85/107) in group 1 and 91% (104/114) in group 2 received the recommended dose of IV antibiotic for their body weight (e.g., 2 g cefazolin for patients of >80 kg) (P < 0.006). CONCLUSIONS: Optimal treatment of open fracture patients with early and appropriate antibiotic prophylaxis was lacking for many patients at our trauma center. A multifaceted performance improvement program specifically concentrating on education, accountability, and antibiotic availability aimed at this aspect of orthopaedic trauma care was very effective in improving our early treatment of these patients. LEVEL OF EVIDENCE: Therapeutic level III. See instructions for authors for a complete description of levels of evidence.

MALP-2 pre-treatment modulates systemic inflammation in hemorrhagic shock.

BACKGROUND: TLR-2 is expressed on the surface of leucocytes, lung and liver tissue and initiates the activation of immune response after interaction with components of the bacterial cell wall. In this experiment we investigated whether immunostimulation with TLR-2 agonists under conditions of sterile inflammation (hemorrhagic shock (HS)) may affect the immune response and remote organ inflammation. METHODS: Male C57/BL6 mice were subjected to standardized pressure-controlled HS (MAP of 35 mmHg for 90 minutes). The TLR-2 agonist macrophage-activated lipopeptide-2 (MALP-2) was administered (i.p.) either 12 hours prior to the induction of HS (Group MALP PT) or after the hypotensive period (90 minutes) (Group MALP T). After six hours, plasma cytokine levels (IL-6, KC, IL-10, and MCP-1) and lung and liver MPO activity were assessed. RESULTS: Pre-treatment with MALP-2 resulted in a significant attenuation of the systemic pro-inflammatory (IL-6) response (MALP PT: 0.83±0.2 ng/ml vs. MALP T: 1.7±0.09 ng/ml) (p<0.05). In comparison to the liver MPO activity, lung MPO levels in in group MALP PT did not show differences to levels measured in MALP T mice (1.200±200 ng/mg vs. 1.800±200 ng/mg). CONCLUSIONS: After initial inflammation, MALP-2 pre-treatment was associated with attenuated systemic immune response after sterile stimulus. The TLR-2 agonist appears to affect sterile inflammation pathways. The exact mechanisms should be studied further to better understand these affects.

Predictors of poor outcome after both column acetabular fractures: a 30-year retrospective cohort study.

BACKGROUND AND PURPOSE: Acetabular fractures are often combined with associated injuries to the hip joint. Some of these associated injuries seem to be responsible for poor long-term results and these injuries seem to affect the outcome independent of the quality of the acetabular reduction. The aim of our study was to analyze the outcome of both column acetabular fractures and the influence of osseous cofactors such as initial fracture displacement, hip dislocation, femoral head lesions and injuries of the acetabular joint surface. METHODS: A retrospective cohort study in patients with both column acetabular fractures treated over a 30 year period was performed. Patients with a follow-up of more than two years were invited for a clinical and radiological examination. Displacement was analyzed on initial and postoperative radiographs. Contusion and impaction of the femoral head was grouped. Injuries of the acetabular joint surface consisting of impaction, contusion and comminution were recorded. The Merle d'Aubigné Score was documented and radiographs were analysed for arthritis (Helfet classification), femoral head avascular necrosis (Ficat/Arlet classification) and heterotopic ossifications (Brooker classification). RESULTS: 115 patients were included in the follow up examination. Anatomic reduction (malreduction ≤ 1mm) was associated with a significantly better clinical outcome than nonanatomical reduction (p = 0.001). Initial displacement of more than 10mm (p = 0.031) and initial intraarticular fragments (p = 0.041) were associated with worse outcome. Other associated injuries, such as the presence of a femoral head dislocation, femoral head injuries and injuries to the acetabular joint surface showed no significant difference in outcome individually, but in fractures with more than two associated local injuries the risk for joint degeneration was significant higher (p < 0.001) than in cases with less than two of them.In the subgroup of anatomically reconstructed fractures no significant influence of the analyzed cofactors could be observed. CONCLUSION: Anatomical reduction appears to be an important parameter for a good clinical outcome in patients with both column acetabular fractures. Additional fracture characteristics such as the initial displacement and intraarticular fragments seem to influence the results. Patients should also be advised that both column acetabular fractures with more than two additional associated factors have a significantly higher risk of joint degeneration.

Increased morbidity and mortality after bilateral femoral shaft fractures: myth or reality in the era of damage control?

INTRODUCTION: Bilateral femoral shaft fractures have been reported to be an independent risk factor for morbidity and mortality; however, the value of these studies is limited due to small sample sizes and the timing of these studies before the establishment of damage control orthopaedics. The objective of this study was to compare the incidence of morbidity and mortality in patients with bilateral vs. unilateral femoral shaft fractures in the era of damage control orthopaedics. METHODS: Retrospective analysis of the TraumaRegister DGU from 2002 to 2005. Inclusion criteria were uni- or bilateral femoral shaft fractures and complete demographic data documentation. Univariate data analysis and logistic regression analysis were performed with SPSS. RESULTS: Between 2002 and 2005, 776 patients with unilateral and 118 patients with bilateral femoral shaft fractures were identified. Patients with bilateral femoral shaft fractures had a significantly higher Injury Severity Score (ISS) (29.5 vs. 25.7 points), a significantly higher incidence of pulmonary (34.7% vs. 20.6%) and multiple organ failure (25.0% vs. 14.6%) as well as a significantly higher mortality rate (16.9% vs. 9.4%). In the overall patient population, early total care (ETC) was significantly more often performed in patients with unilateral femoral shaft fractures (50.9% vs. 33.6%). Logistic regression analysis revealed no significant association between bilateral femoral shaft fractures and multiple organ failure or mortality; however, bilateral femoral shaft fractures are an independent risk factor for pulmonary failure. Subgroup analysis revealed that the impact of the bilateral femoral shaft fracture was especially pronounced in patients with an ISS<25 points. DISCUSSION: Bilateral femoral shaft fractures are an independent risk factor for pulmonary failure but not for multiple organ failure or mortality. The impact of the additional femoral shaft fracture for pulmonary failure appears to be especially pronounced in the less severely injured patients, whose injuries are often underestimated when stratified with the ISS. Patients with bilateral femoral shaft fractures have significantly more often severe abdominal injuries as well as severe blood loss which may account for the increased mortality rate. Therefore, the presence of bilateral femoral shaft fractures should be recognised as an increased risk for systemic complications.

Damage control orthopedics: current evidence.

PURPOSE OF REVIEW: There is still an ongoing debate whether damage control orthopedics (DCO) or other treatment strategies should be favored in the treatment of multiply injured patients. This review gives an overview of the current literature concerning this important question in the treatment of severely injured patients. RECENT FINDINGS: Several studies could show that DCO can reduce the inflammatory burden due to surgery (second hit). The only randomized study showed a benefit for borderline patients treated by DCO in comparison to early total care. Other studies showed advantages for early care treatment in similar patients. SUMMARY: In severely injured patients, DCO should be considered. On the other hand, there is still a lack of randomized studies for a more precise characterization of the patients who benefit from DCO treatment.

Outcome after thoracoscopic ventral stabilisation of thoracic and lumbar spine fractures.

BACKGROUND AND PURPOSE: Thoracoscopic-assisted ventral stabilisation for thoracolumbar fractures has been shown to be associated with decreased recovery time and less morbidity when compared with open procedures. However, there are a limited number of studies evaluating late clinical and radiological results after thoracoscopic spinal surgery. METHODS: We performed an analysis of the late outcomes of thoracolumbar fractures after minimally invasive thoracoscopic ventral instrumentation. Between August 2003 and December 2008, 70 patients with thoracolumbar fractures (T5-L2) underwent ventral thoracoscopic stabilisation. Tricortical bone grafts, anterior plating systems (MACS-System), and cage implants were used for stabilisation. Outcomes measured include radiologic images (superior inferior endplate angle), Visual Analogue Scale (VAS), VAS Spine Score, quality of life scores SF-36 and Oswestry Disability Index (ODI). RESULTS: Forty seven patients (67%, 47 out of 70) were recruited for the follow up evaluation (2.2 ± 1.5 years). Lower VAS Spine scores were calculated in patients with intra- or postoperative complications (44.7 (± 16.7) vs. 65.8 (± 24.5), p=0.0447). There was no difference in outcome between patients treated with bone graft vs. cage implants. Loss of correction was observed in both bone graft and titanium cage groups. INTERPRETATION: The present study demonstrates diminished long-term quality of life in patients treated with thoracoscopic ventral spine when compared with the outcome of german reference population. In contrast to the other patients, those patients without intra-operative or post-operative complications were associated with improved outcome. The stabilisation method (bone graft versus spinal cage) did not affect the long-term clinical or radiographic results in this series.

Fibula fracture stabilization with a guide wire as supplementary fixation in tibia fractures.

The tibia is the most commonly fractured long bone. Although the goals of fracture management are straightforward, methods for achieving anatomical alignment and stable fixation are limited. Type of management depends on fracture pattern, local soft-tissue involvement, and systemic patient factors. Tibial shaft fractures with concomitant fibula fractures, particularly those at the same level, may be difficult to manage because of their inherent instability. Typically, management of lower extremity fractures is focused on the tibia fixation, and the associated fibula fracture is managed without fixation. In this article, we describe a novel technique for intramedullary fixation of the fibula, using a humeral guide wire as an adjunct to tibia fixation in the setting of tibial shaft fracture. This technique aids in determining length, alignment, and rotation of the tibia fracture and may help support the lower extremity as whole by stabilizing the lateral column. In addition, this technique can be used to help maintain reduction of the fibula when there is concern about the soft tissues of the lower extremity secondary to swelling or injury. Our clinical case series demonstrates the safety, effectiveness, and cost-sensitivity of this technique in managing select concurrent fractures of the tibia and fibula.

Inhalative vs. systemic IL-10 administration: differences in the systemic inflammatory response and end-organ inflammation following hemorrhagic shock.

Interleukin-10 is known to modulate the systemic inflammatory response after trauma. This study investigates differences in the systemic and end-organ inflammation in animals treated with either inhalative or systemic IL-10 after experimental hemorrhagic shock (HS). Pressure controlled HS was performed in C57/BL6 mice for 1.5h (6 animals per group). Inhalative or systemic recombinant mouse IL-10 (50 µg/kg dissolved in 50 µl PBS) was administered after resuscitation. Animals were sacrificed after 4.5 or 22.5h of recovery. Serum levels of IL-6, IL-10, KC, MCP-1, and LBP were determined by ELISA. Pulmonary and liver inflammation was analyzed by standardized Myeloperoxidase (MPO) kits. Systemic and inhalative IL-10 administration affected the systemic inflammatory response as well as end-organ inflammation differently. Differences were obvious in the early (6h) but not later (24h) inflammatory phase. Systemic IL-10 application was associated with a decreased systemic inflammatory response as well as hepatic inflammation, whereas nebulized IL-10 solely reduced the pulmonary inflammation. Our study demonstrates that systemic and nebulized IL-10 administration differentially influenced the systemic cytokine response and end-organ inflammation. Early pulmonary but not hepatic protection appears to be possible by inhalative IL-10 application. Further studies are necessary to assess exact pathways.

The academic medical centre and nongovernmental organisation partnership following a natural disaster.

The global response to the 12 January 2010 earthquake in Haiti revealed the ability to mobilise medical teams quickly and effectively when academic medical centres partner non-governmental organisations (NGO) that already have a presence in a zone of devastation. Most established NGOs based in a certain region are accustomed to managing the medical conditions that are common to that area and will need additional and specialised support to treat the flux of myriad injured persons. Furthermore, an NGO with an established presence in a region prior to a disaster appears better positioned to provide sustained recovery and rehabilitation relief. Academic medical centres can supply these essential specialised resources for a prolonged time. This relationship between NGOs and academic medical centres should be further developed prior to another disaster response. This model has great potential with regard to the rapid preparation and worldwide deployment of skilled medical and surgical teams when needed following a disaster, as well as to the subsequent critical recovery phase.

Complications of anterior subcutaneous internal fixation for unstable pelvis fractures: a multicenter study.

BACKGROUND: Stabilization after a pelvic fracture can be accomplished with an anterior external fixator. These devices are uncomfortable for patients and are at risk for infection and loosening, especially in obese patients. As an alternative, we recently developed an anterior subcutaneous pelvic internal fixation technique (ASPIF). QUESTIONS/PURPOSES: We asked if the ASPIF (1) allows for definitive anterior pelvic stabilization of unstable pelvic injuries; (2) is well tolerated by patients for mobility and comfort; and (3) has an acceptable complication rate. METHODS: We retrospectively reviewed 91 patients who incurred an unstable pelvic injury treated with an anterior internal fixator and posterior fixation at four Level I trauma centers. We assessed (1) healing by callous formation on radiographs and the ability to weightbear comfortably; (2) patient function by their ability to sit, stand, lie on their sides, and how well they tolerated the implants; and (3) complications during the observation period. The minimum followup was 6 months (mean, 15 months; range, 6-40 months). RESULTS: All 91 patients were able to sit, stand, and lie on their sides. Injuries healed without loss of reduction in 89 of 91 patients. Complications included six early revisions resulting from technical error and three infections. Irritation of the lateral femoral cutaneous nerve was reported in 27 of 91 patients and resolved in all but one. Heterotopic ossification around the implants, which was asymptomatic in all cases, occurred in 32 of 91 patients. CONCLUSIONS: The anterior internal fixator provided high rates of union for the anterior injury in unstable pelvic fractures. Patients were able to sit, stand and ambulate without difficulty. Infections and aseptic loosening were reduced but heterotopic ossification and irritation of the LFCN are common. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Fibular fracture stabilization with a guidewire as supplementary fixation in tibia fractures.

We present a novel technique of intramedullary fixation of the fibula using a humeral guide wire as an adjunct to tibial fixation, in the setting of tibial shaft fracture. Not only does this technique aid in determining length, alignment, and rotation of the tibial fracture, but it may also help the support of the lower extremity as whole by stabilizing the lateral column. In addition, this technique can be used to help maintain reduction of the fibula when there is concern for the soft tissues of the lower extremity secondary to swelling or injury. Our clinical case series demonstrates this safe, effective, and cost-sensitive technique to be used in the treatment of select concurrent fractures of the tibia and fibula.

Evolution of operative interventions by two university-based surgical teams in Haiti during the first month following the earthquake.

BACKGROUND: The earthquake that struck Haiti on 10 January 2010, killed 200,000 persons and injured thousands more. Working with Partners in Health, a non-governmental organization already present in Haiti, Dartmouth College, and the University of Pennsylvania sent multidisciplinary surgical teams to hospitals in the villages of Hinche and Cange. The purpose of this report is to describe the injuries seen and evolution of treatments rendered at these two outlying regional hospitals during the first month following the earthquake. METHODS: A retrospective review of the database maintained by each team was performed. In addition to a list of equipment taken to Haiti, information collected included patient age, American Society of Anesthesiology (ASA) physical status, injuries sustained, procedures performed, wound management strategy, antibiotic therapy, and early outcomes. RESULTS: A total of 113 surgical procedures were performed in 15 days by both teams. The average patient age was 25 years and average ASA score was 1.4. The majority of injuries involved large soft tissue wounds and closed fractures, although 21-40% of the patients at each hospital had either an open fracture or amputation wound. Initially, wound debridement was the most common procedure performed, but after two weeks, skin grafting, fracture fixation, and amputation revision were the more commonly needed operations. CONCLUSIONS: Academic surgical teams can ameliorate the morbidity and mortality following disasters caused by natural hazards by partnering with organizations that already have a presence in the affected region. A multidisciplinary team of surgeons and nurses can improve both mortality and morbidity following a disaster.

Open tibial shaft fractures: II. Definitive management and limb salvage.

Definitive treatment of open fractures of the tibial diaphysis is challenging. The high-energy nature of these fractures, as well as the contamination of the fracture site and devitalization of the soft-tissue envelope, greatly increases the risk of infection, nonunion, and wound complications. The goals of definitive treatment include wound coverage or closure; prevention of infection; restoration of length, alignment, rotation, and stability; fracture healing; and return of function. Advances in orthobiologics, modern plastic surgical techniques, and fracture stabilization methods, most notably locked intramedullary nailing, have led to improved prognosis for functional recovery and limb salvage. Despite improved union and limb salvage rates, the prognosis for severe type III open fracture of the tibial shaft remains guarded, and outcomes are often determined by patient psychosocial variables.

Open tibial shaft fractures: I. Evaluation and initial wound management.

Open fractures of the tibial diaphysis are often associated with severe bone and soft-tissue injury. Contamination of the fracture site and devitalization of the soft-tissue envelope greatly increase the risk of infection, nonunion, and wound complications. Management of open tibial shaft fractures begins with a thorough patient evaluation, including assessment of the bone and soft tissue surrounding the tibial injury. Classification of these injuries according to the system of Gustilo and Anderson at the time of surgical débridement is useful in guiding treatment and predicting outcomes. Administration of antibiotic prophylaxis as soon as possible after injury as well as urgent and thorough débridement, irrigation, and bony stabilization are done to minimize the risk of infection and improve outcomes. The use of antibiotic bead pouches and negative-pressure wound therapy has proved to be efficacious for the acute, temporary management of severe bone and soft-tissue defects.

Ceramic hemi-unicondylar arthroplasty in an adolescent patient with idiopathic tibial chondrolysis.

Despite recent advances in cartilage regeneration and restoration procedures, isolated, large, full-thickness cartilage lesions in young patients continue to pose significant challenges to patients and orthopedic surgeons. Treatment options for this difficult problem have traditionally included arthrodesis, osteotomy, osteochondral allograft, and prosthetic reconstruction. We present a case of an adolescent patient with isolated idiopathic lateral tibial chondrolysis treated with a custom ceramic hemi-unicondylar hemiarthroplasty. Preoperatively, a 3-dimensional computed tomography scan of the patient's knee was obtained to begin manufacturing a conforming custom ceramic insert that would articulate between the tibial base plate and the patient's native lateral femoral cartilage. Through a lateral parapatellar approach, the tibial preparation was carried out using the Zimmer M/G unicompartmental knee system (Warsaw, Indiana), and the tibial base plate was cemented into position in the standard fashion. A custom, conforming, prefabricated ceramic insert (CeramTec, Memphis, Tennessee) was then inserted onto the tibial base plate. At 5-year follow-up, this salvage procedure was successful in relieving pain and restoring function in this young patient. There were no signs of implant loosening or lysis. Magnetic resonance imaging of the knee at last follow-up revealed that the cartilage thickness of the patient's lateral femoral condyle remained unchanged. Unicondylar hemiarthroplasty performed in patients with large unipolar lesions in the knee can provide durable and reliable pain relief. Ceramic is a viable material that can be considered for articulation with native cartilage.

Kinase-independent functions for Itk in TCR-induced regulation of Vav and the actin cytoskeleton.

The Tec family kinase Itk is an important regulator of Ca(2+) mobilization and is required for in vivo responses to Th2-inducing agents. Recent data also implicate Itk in TCR-induced regulation of the actin cytoskeleton. We have evaluated the requirements for Itk function in TCR-induced actin polarization. Reduction of Itk expression via small interfering RNA treatment of the Jurkat human T lymphoma cell line or human peripheral blood T cells disrupted TCR-induced actin polarization, a defect that correlated with decreased recruitment of the Vav guanine nucleotide exchange factor to the site of Ag contact. Vav localization and actin polarization could be rescued by re-expression of either wild-type or kinase-inactive murine Itk but not by Itk containing mutations affecting the pleckstrin homology or Src homology 2 domains. Additionally, we find that Itk is constitutively associated with Vav. Loss of Itk expression did not alter gross patterns of Vav tyrosine phosphorylation but appeared to disrupt the interactions of Vav with SLP-76. Expression of membrane-targeted Vav, Vav-CAAX, can rescue the small interfering RNA to Itk-induced phenotype, implicating the alteration in Vav localization as directly contributing to the actin polarization defect. These data suggest a kinase-independent scaffolding function for Itk in the regulation of Vav localization and TCR-induced actin polarization.

SAP regulates T(H)2 differentiation and PKC-theta-mediated activation of NF-kappaB1.

XLP is caused by mutations affecting SAP, an adaptor that recruits Fyn to SLAM family receptors. SAP-deficient mice recapitulate features of XLP, including increased T cell activation and decreased humoral responses post-infection. SAP-deficient T cells also show increased TCR-induced IFN-gamma and decreased T(H)2 cytokine production. We demonstrate that the defect in IL-4 secretion in SAP-deficient T cells is independent of increased IFN-gamma production. SAP-deficient cells respond normally to polarizing cytokines, yet show impaired TCR-mediated induction of GATA-3 and IL-4. Examination of TCR signaling revealed normal Ca(2+) mobilization and ERK activation in SAP-deficient cells, but decreased PKC-theta recruitment, Bcl-10 phosphorylation, IkappaB-alpha degradation, and nuclear NF-kappaB1/p50 levels. Similar defects were observed in Fyn-deficient cells. SLAM engagement amplified PKC-theta recruitment in wt but not SAP- or Fyn-deficient cells, arguing that a SAP/Fyn-mediated pathway enhances PKC-theta/NF-kappaB1 activation and suggesting a role for this pathway in T(H)2 regulation.

Requirement for Tec kinases in chemokine-induced migration and activation of Cdc42 and Rac.

Cell polarization and migration in response to chemokines is essential for proper development of the immune system and activation of immune responses. Recent studies of chemokine signaling have revealed a critical role for PI3-Kinase, which is required for polarized membrane association of pleckstrin homology (PH) domain-containing proteins and activation of Rho family GTPases that are essential for cell polarization and actin reorganization. Additional data argue that tyrosine kinases are also important for chemokine-induced Rac activation. However, how and which kinases participate in these pathways remain unclear. We demonstrate here that the Tec kinases Itk and Rlk play an important role in chemokine signaling in T lymphocytes. Chemokine stimulation induced transient membrane association of Itk and phosphorylation of both Itk and Rlk, and purified T cells from Rlk(-/-)Itk(-/-) mice exhibited defective migration to multiple chemokines in vitro and decreased homing to lymph nodes upon transfer to wt mice. Expression of a dominant-negative Itk impaired SDF-1alpha-induced migration, cell polarization, and activation of Rac and Cdc42. Thus, Tec kinases are critical components of signaling pathways required for actin polarization downstream from both antigen and chemokine receptors in T cells.