52 research outputs found
Comparative studies of rat IgG to further delineate the Fc: FcRn interaction site
No full textRecent data have indicated that the MHC class I-related receptor, FcRn, regulates the half-lives of serum IgG in addition to its known role in transferring IgG from mother to young. In the current study, the activity of rat IgG (rlgG) isotypes in FcRn-mediated functions has been analyzed. The serum half-life and maternofetal transfer in mice decreased in the order rlgG2a > rlgG1 > rlgG2c > rlgG2b. This decrease in activity correlates well with reduced binding affinity for soluble mouse FcRn, and site-directed mutagenesis of a recombinant Fc-hinge fragment has been used to investigate the molecular basis for the differences in activities of the rlgG. Analysis of the serum half-lives of the mutated Fc-hinge fragments demonstrated that, in addition to Ile253, His310, His435 and His436 that were identified in earlier studies, amino acids at positions 257, 307 acid 309 play a role in building the FcRn interaction site of IgG. The study also excludes the involvement of amino acids in a fourth loop located at the CH2-CH3 domain interface that encompasses residues 386-387 in FcRn binding. Sequence differences at positions 257, 307 and 309 between rlgG most likely account for the reduced affinity of rlgG2b and IgG2c relative to rlgG1 and rlgG2a for binding to FcRn.</p
The Effect of Chronic Psychological Stress on the Cutaneous Immune Response in the Development of a Contact Hypersensitivity Reaction
No full textIncreasing evidence demonstrates that psychological stress can have an impact on the cutaneous immune response. While there have been many studies examining the impact of acute stress on an allergic contact dermatitis model, there are few studies concerning the impact of chronic psychological stress. Furthermore, the mechanism of the impact of chronic stress on contact hypersensitivity remains to be fully explored. Here we show that chronic restraint stress induces activation of the hypothalamus-pituitary-adrenal axis and delays weight gain in female BALB/c mice. In addition, we observed that chronic psychological stress reduces the cutaneous immune response in a contact hypersensitivity reaction. This suppression was not observed 30 days after stress cessation, suggesting the impact of chronic stress is a transient occurrence. Additionally, chronic stress does not influence T cell proliferation, activation, or sensitivity to glucocorticoids. In response to contact hypersensitivity, chronic stress induces a decrease in overall circulating white blood cells, lymphocytes, and monocytes. This correlated to decreased dermal infiltrate and increased percentages of CD4+ and CD8+ T cells in auricular lymph nodes. In addition, decreased amounts of local IFN-γ were observed in inflamed ear tissue of chronically stressed mice. Overall, the results suggest that chronic psychological stress reduces contact hypersensitivity reactions in a relatively transient manner and disrupts local immune cell trafficking resulting in reduced IFN-γ production
Extracellular Superoxide Dismutase Indirectly Enhances the Release of Immature Neutrophils from the Murine Bone Marrow
No full textExtracellular superoxide dismutase (ecSOD) regulates extracellular concentrations of reactive oxygen species (ROS) to protect tissues during infection and inflammation. Using ecSOD HI, ecSOD WT, and ecSOD KO mice, we have previously shown that ecSOD activity enhances neutrophil recruitment to the liver, yet inhibits the innate immune response against Listeria monocytogenes leading to increased host susceptibility. Using adoptive transfer experiments, we observed that ecSOD activity does not affect neutrophil recruitment or function in a cell-intrinsic manner. Additionally, we noted that ecSOD activity results in decreased retention of immature neutrophils in the bone marrow without altering granulopoiesis. Furthermore, we determined that ecSOD activity protects the extracellular matrix (ECM) and increases concentrations of neutrophil-attracting chemokines leading to an increase in immature neutrophils in the liver.
Since ecSOD can be produced by cells from the hematopoietic lineage as well as non-hematopoietic cells, we used bone marrow chimeric mice to investigate the relative contribution of ecSOD produced by cells from each lineage. Ultimately, it was determined that ecSOD from both hematopoietic and non-hematopoietic cells contributes to the overall phenotype observed in ecSOD congenic mice. Collectively, our data suggest that ecSOD activity inhibits degradation of the ECM and promotes egress of immature neutrophils out of the bone marrow and into the liver where they provide inadequate protection against L. monocytogenes. These studies highlight the potential therapeutic value of ecSOD inhibitors to enhance immune responses during bacterial infections
Effect of CD44 Expression on T Cell Acute Lymphocytic Leukemia
No full textCD44 is a cell surface glycoprotein that serves as a multifunctional receptor aiding in trafficking and adhesion of immune cells. CD44 also serves as a recruitment platform for signaling molecules and has been shown to regulate proliferation. In several types of leukemia the presence or absence of CD44 expression is associated with different clinical outcomes, with patients who have increased expression of CD44 exhibiting a stronger response to conventional chemo- and radiotherapy. By using Jurkat T cells, which do not express CD44, to determine the effects of CD44 expression in a model Acute Lymphocytic Leukemia cell line, we have outlined two major areas of study. Firstly, upon expression of CD44, Jurkat T cells proliferate slowly compared to the control cells. This decrease in proliferation is coupled to an arrest in the cell cycle during the transition from the G1 phase into S phase. The dysregulation of the cell cycle induced by CD44 also leads to the induction of aneuploidy. CD44 expressing Jurkat T cells have reduced mRNA expression for several key regulators of chromosome separation and the mitotic spindle complex. This finding, coupled with decreased EGR-1 expression, which controls the cyclins responsible for transition from G1 into S phase, leads to an unstable cell phenotype which proliferates slowly and accumulates extra chromosomes in daughter cells. The second area of study focuses on the mechanism by which CD44 expression at the cell surface results in the observed decreases in proliferation, Akt activation, and EGR-1 expression. We observed that CD44 expressing Jurkat cells show four to five times higher calcium influx when at rest compared to the vector control cells. This influx in calcium is due to CD44 expression activating a cell surface inducible calcium release activated calcium channel. The excess calcium activates calcium-activated phosphatases and kinases, disrupting EGR-1 expression and inducing a hypophosphorylation of Akt. Together, these findings indicate that CD44 expression can regulate cell proliferation and signal transduction pathways in addition to its role in adhesion. Thus, our data provide a further understanding of how CD44 expression modifies leukemic cells into cells that are favorable for therapeutic intervention
The Role of IL-23 in Regulating the Recruitment and Function of Phagocytic Cells during Listeria monocytogenes infection
No full textThe IL-23/IL-17 axis is detrimental during autoimmune disorders, but is protective against certain pathogens, particularly extracellular bacteria. We have previously shown that IL-23 is required for host resistance against Listeria monocytogenes (LM) and for neutrophil recruitment to the liver, but not the spleen, during infection. Despite efficient neutrophil recruitment to the spleen, IL-23p19 knockout (KO) mice have an increased bacterial burden in this organ compared to C57BL/6 (B6) mice. Interestingly, specific depletion of neutrophils abrogated the differences in bacterial burden in the liver, but not the spleen of B6 and IL-23p19 KO mice, suggesting that IL-23 may regulate the recruitment/function of another cell type in the spleen. Accordingly, LM-infected IL- 23p19 KO mice had fewer inflammatory monocytes in the spleen as well as a reduction in monocyte-recruiting chemokines compared to B6 mice. Therefore, IL-23 is necessary for the optimal recruitment of inflammatory monocytes to the spleen during LM infection. Phagocytic cells express receptors for IL-23 and IL-17A suggesting that the activity of these cells could be regulated by IL-23 or IL-17A. However, it is not known whether IL-23 could impact the function of phagocytic cells during LM infection. Inflammatory monocytes, neutrophils, and macrophages from B6 and IL-23p19 KO mice displayed equivalent phagocytic potential. Although exogenous stimulation with IL-23 and IL-6 increased the production of ROS from B6 neutrophils, the absence of IL-23 did not impact the ability of inflammatory monocytes and neutrophils to make ROS during LM infection. Additionally, the expression of myeloperoxidase (MPO), inducible nitric oxide (iNOS), and TNF-α by inflammatory monocytes, neutrophils, and peritoneal macrophages was not altered by the lack of IL-23 during LM infection. Therefore, IL-23 is not required for the optimal function of phagocytic cells during LM infection. The proinflammatory mediators, TNF-α and NO, are essential for protection against LM. Surprisingly, there was a reduction in the overall levels of TNF-α and NO in the spleen of IL-23p19 KO mice compared to B6 mice during LM infection. However, exogenous stimulation with IL-23 or IL-17A did not induce or enhance the production of these proinflammatory mediators from splenocytes isolated from LM-infected B6 mice. Interestingly, the reduction in overall production of TNF-α and NO. in the spleens of LMinfected IL-23p19 KO mice, corresponds with reduced numbers and percentages of TNF- α and iNOS-expressing monocytes. This deficient recruitment of inflammatory monocytes resulted in decreased production of monocyte-derived TNF-α and NO, leading to increased bacterial burdens in the spleens of LM-infected IL-23p19 KO mice. Collectively, our data reveal that the enhanced susceptibility of IL-23p19 KO mice is not due to functional impairment of phagocytic cells, instead it is caused by the inefficient recruitment of neutrophils to the liver, and inflammatory monocytes to the spleen, during LM infection
Langerhans Cells in CD44-Deficient Mice Emigrate from the Epidermis But Fail to Reach the Lymph Nodes After Hapten Application
No full textStability in antigenic reactivity of the major outer surface protein, OspA, in borrelia burgdorferi, during persistent infection in Syrian hamsters
No full textThe spirochete Borrelia burgdorferi is the causative agent of Lyme disease, a multisystem disorder that can cause a variety of disorders in susceptible mammalian hosts. The immune response of infected mammals, including humans, is ineffective in clearing B. burgdorferi as demonstrated by the ability to reisolate the spirochete from naturally and experimentally infected hosts after extended periods of time. Recent evidence suggests that this pathogen evades the immune response in part through changes in antigenic reactivity.The purpose of this study was to determine if outer surface protein A (OspA) of B. burqdorferi varies in the course of infection in Syrian hamsters and thus potentially plays a role in evading the host immune response. To assess the degree of change, differences in the binding of a murine monoclonal antibody (H5332) were measured using IFA and ELISA techniques over a 9-week period of time.Results of this study suggest that OspA is persistently expressed in infected Syrian hamsters for at least 9-weeks. Moreover, this protein, or at least the epitope that H5332 binds with, is stably expressed. These results indicate OspA, or at least the epitope of OspA that I probed, does not appear to contribute to the evasive mechanisms of 8. burgdorferi in Syrian hamsters.Thesis (M.S.)Department of Biolog
Psychological Stress as a Determinant of Skin Barrier Function: Immunological Pathways and Therapeutic Opportunities
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Effects of secondary forces on the ligand binding properties and variable domain conformations of a monoclonal anti-fluorescyl antibody
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