Rgs1 and Gnai2 Regulate the Entrance of B Lymphocytes into Lymph Nodes and B Cell Motility within Lymph Node Follicles

SummarySignaling by G protein-coupled receptors coupled to Gαi assists in triggering lymphocyte movement into and out of lymph nodes. Here, we show that modulating the signaling output from these receptors dramatically alters B cell trafficking. Intravital microscopy of adoptively transferred B cells from wild-type and Rgs1−/− mice revealed that Rgs1−/− B cells stick better to lymph node high endothelial venules, home better to lymph nodes, and move more rapidly within lymph node follicles than do wild-type B cells. In contrast, B cells from Gnai2−/− mice enter lymph nodes poorly and move more slowly than do wild-type B cells. The Gnai2−/− mice often lack multiple peripheral lymph nodes, and their B cells respond poorly to chemokines, indicating that Gαi1 and Gαi3 poorly compensate for the loss of Gαi2. These results demonstrate opposing roles for Rgs1 and Gnai2 in B cell trafficking into and within lymph nodes

Abnormal B-Cell Responses to Chemokines, Disturbed Plasma Cell Localization, and Distorted Immune Tissue Architecture in Rgs1(−/−) Mice

Normal lymphoid tissue development and function depend upon chemokine-directed cell migration. Since chemokines signal through heterotrimeric G-protein-coupled receptors, RGS proteins, which act as GTPase-activating proteins for Gα subunits, likely fine tune the cellular responses to chemokines. Here we show that Rgs1(−/−) mice possess B cells that respond excessively and desensitize improperly to the chemokines CXCL12 and CXCL13. Many of the B-cell follicles in the spleens of Rgs1(−/−) mice have germinal centers even in the absence of immune stimulation. Furthermore, immunization of these mice leads to exaggerated germinal center formation; partial disruption of the normal architecture of the spleen and Peyer's patches; and abnormal trafficking of immunoglobulin-secreting cells. These results reveal the importance of a regulatory mechanism that limits and desensitizes chemokine receptor signaling

APPLICATION OF HIGH-INTENSITY FOCUSED ULTRASOUND TO THE STUDY OF MILD TRAUMATIC BRAIN INJURY

Though intrinsically of much higher frequency than open-field blast overpressures, high-intensity focused ultrasound (HIFU) pulse trains can be frequency modulated to produce a radiation pressure having a similar form. In this study, 1.5-MHz HIFU pulse trains of 1-ms duration were applied to intact skulls of mice in vivo and resulted in blood-brain barrier disruption and immune responses (astrocyte reactivity and microglial activation). Analyses of variance indicated that 24 h after HIFU exposure, staining density for glial fibrillary acidic protein was elevated in the parietal and temporal regions of the cerebral cortex, corpus callosum and hippocampus, and staining density for the microglial marker, ionized calcium binding adaptor molecule, was elevated 2 and 24 h after exposure in the corpus callosum and hippocampus (all statistical test results, p\u3c0.05). HIFU shows promise for the study of some bio-effect aspects of blast-related, non-impact mild traumatic brain injuries in animals

Anti-ribonucleoprotein antibodies mediate enhanced lung injury following mesenteric ischemia/reperfusion in Rag-1−/− mice

Natural Abs and autoantibodies bind antigens displayed by ischemia-conditioned tissues, followed by complement activation and enhanced tissue injury during reperfusion. Anti-ribonucleoprotein (RNP) Ab is associated with lung disease in patients with autoimmune disease but it is not known whether these abs contribute to lung injury. Mesenteric I/R in mice leads to local and remote lung injury. Accordingly, we used this model to investigate whether anti-RNP Abs would reconstitute I/R damage with prominent lung damage in injury-resistant Rag1− / − animals. Rag1− / − mice injected with anti-RNP Ab containing serum and subjected to mesenteric I/R suffered greater intestinal injury than control-treated and sham-operated animals. The magnitude of the reconstituted damage was anti-RNP Ab titer-dependent. Anti-RNP Ab-treated animals demonstrated a dose-dependent increase in lung histologic injury scores compared to control and sham animals. Anti-RNP mediated injury was shown to be complement dependent. These experiments reveal a novel mechanism whereby anti-RNP Abs contributes to the development of pulmonary pathology in patients with autoimmune diseases following exposure of remote organs to I/R injury