A central role for DOCK2 during interstitial lymphocyte motility and sphingosine-1-phosphate-mediated egress

Recent observations using multiphoton intravital microscopy (MP-IVM) have uncovered an unexpectedly high lymphocyte motility within peripheral lymph nodes (PLNs). Lymphocyte-expressed intracellular signaling molecules governing interstitial movement remain largely unknown. Here, we used MP-IVM of murine PLNs to examine interstitial motility of lymphocytes lacking the Rac guanine exchange factor DOCK2 and phosphoinositide-3-kinase (PI3K)gamma, signaling molecules that act downstream of G protein-coupled receptors, including chemokine receptors (CKRs). T and B cells lacking DOCK2 alone or DOCK2 and PI3Kgamma displayed markedly reduced motility inside T cell area and B cell follicle, respectively. Lack of PI3Kgamma alone had no effect on migration velocity but resulted in increased turning angles of T cells. As lymphocyte egress from PLNs requires the sphingosine-1-phosphate (S1P) receptor 1, a G(alphai) protein-coupled receptor similar to CKR, we further analyzed whether DOCK2 and PI3Kgamma contributed to S1P-triggered signaling events. S1P-induced cell migration was significantly reduced in T and B cells lacking DOCK2, whereas T cell-expressed PI3Kgamma contributed to F-actin polymerization and protein kinase B phosphorylation but not migration. These findings correlated with delayed lymphocyte egress from PLNs in the absence of DOCK2 but not PI3Kgamma, and a markedly reduced cell motility of DOCK2-deficient T cells in close proximity to efferent lymphatic vessels. In summary, our data support a central role for DOCK2, and to a lesser extent T cell-expressed PI3Kgamma, for signal transduction during interstitial lymphocyte migration and S1P-mediated egress.

Survival of bonded lingual retainers with chemical or photo polymerization over a 2-year period: a single-center, randomized controlled clinical trial

INTRODUCTION The objective of this trial was to compare the survival rates of mandibular lingual retainers bonded with either chemically cured or light-cured adhesive after orthodontic treatment. METHODS Patients having undergone orthodontic treatment at a private orthodontic office were randomly allocated to fixed retainers placed with chemically cured composite or light-cured composite. Eligibility criteria included no active caries, restorations, or fractures on the mandibular anterior teeth, and adequate oral hygiene. The main outcome was any type of first-time lingual retainer breakage; pattern of failure (adapted adhesive remnant index scores) was a secondary outcome. Randomization was accomplished with random permuted blocks of 20 patients with allocation concealed in sequentially numbered, opaque, sealed envelopes. Blinding was applicable for outcome assessment only. Patients were reviewed at 1, 3, and 6 months and then every 6 months after placement of the retainer until completion of the study. Data were analyzed using survival analysis including Cox regression; sensitivity analysis was carried out after data imputation for subjects lost to follow-up. RESULTS Two hundred twenty patients (median age, 16 years; interquartile range, 2; range, 12-47 years) were randomized in a 1:1 ratio to either chemical or light curing. Baseline characteristics were similar between groups, the median follow-up period was 2.19 years (range, 0.003-3.64 years), and 16 patients were lost to follow-up. At a minimum follow-up of 2 years, 47 of 110 (42.7%) and 55 of 110 (50.0%) retainers had some type of failure with chemically cured and light-cured adhesive, respectively (log-rank test, P = 0.35). Data were analyzed on an intention-to-treat basis, and the hazard ratio (HR) was 1.15 (95% confidence interval [CI], 0.88-1.70; P = 0.47). There was weak evidence that age is a significant predictor for lingual retainer failures (HR, 0.96; 95% CI, 0.93-1.00; P = 0.08). Adhesive remnant index scoring was possible for only 66 of the 102 (64.7%) failures and did not differ between composites (Fisher exact test, P = 0.16). No serious harm was observed other than gingivitis associated with plaque accumulation. CONCLUSIONS The results of this study indicated no evidence that survival of mandibular lingual retainers differs between chemically and light-cured adhesives. The overall failure rate was 46.4%; however, this included any type of failure, which may have exaggerated the overall failure rate.

Janus kinases 1 and 2 regulate chemokine-mediated integrin activation and naïve T-cell homing.

Janus kinases (JAKs) are central signaling molecules in cytokine receptor cascades. Although they have also been implicated in chemokine receptor signaling, this function continues to be debated. To address this issue, we established a nucleofection model in primary, nonactivated mouse T lymphocytes to silence JAK expression and to evaluate the ability of these cells to home to lymph nodes. Reduced JAK1 and JAK2 expression impaired naïve T-cell migration in response to gradients of the chemokines CXCL12 and CCL21. In vivo homing of JAK1/JAK2-deficient cells to lymph nodes decreased, whereas intranodal localization and motility were unaffected. JAK1 and JAK2 defects altered CXCL12- and CCL21-triggered ezrin/radixin/moesin (ERM) dephosphorylation and F-actin polymerization, as well as activation of lymphocyte function-associated Ag-1 and very late Ag-4 integrins. As a result, the cells did not adhere firmly to integrin substrates in response to these chemokines. The results demonstrate that JAK1/JAK2 participate in chemokine-induced integrin activation and might be considered a target for modulation of immune cell extravasation and therefore, control of inflammatory reactions.