Biomedical subjects

E Sally Ward

Publications and source records attributed to E Sally Ward.

28 records · Page 2Linked to original sources

PubMed2003

The MHC class I related Fc receptor, FcRn, is expressed in the epithelial cells of the human mammary gland.

The major histocompatibility complex (MHC) class I related neonatal Fc receptor (FcRn) plays multiple roles, being involved in transporting immunoglobulin G (IgG) and protecting this antibody class from catabolism. The presence of this receptor was previously demonstrated in the lactating murine mammary gland. In the current study we have investigated FcRn expression in various histologic types of human breast carcinoma and lymph node metastases. We used immunohistochemical methods to demonstrate the presence of FcRn in epithelial cells, whereas this Fc receptor could not be detected in mammary gland endothelial cells. The presence of the receptor was also found in the metastasizing epithelial cells within the lymph nodes, and this provides a useful marker for their identification.

Biological Transport↗

PubMed2003

Evidence to support the cellular mechanism involved in serum IgG homeostasis in humans.

IgG is the most abundant serum antibody and is an essential component of the humoral immune response. It is known that the 'neonatal' Fc receptor (FcRn) plays a role in maintaining constant serum IgG levels by acting as a protective receptor which binds and salvages IgG from degradation. However, the cellular mechanism that is involved in serum IgG homeostasis is poorly understood. In the current study we address this issue by analyzing the intracellular fate in human endothelial cells of IgG molecules which bind with different affinities to FcRn. The studies show that IgG which do not bind to FcRn accumulate in the lysosomal pathway, providing a cellular explanation for short serum persistence of such antibodies. We have also investigated the saturability of the homeostatic system and find that it has limited capacity. Our observations have direct relevance to the understanding and treatment of IgG deficiency, and to the effective application of therapeutic antibodies.

Antibody Affinity↗

PubMed2002

Increasing the affinity of a human IgG1 for the neonatal Fc receptor: biological consequences.

Many biological functions, including control of the homeostasis and maternofetal transfer of serum gamma-globulins, are mediated by the MHC class I-related neonatal FcR (FcRn). A correlation exists in mice between the binding affinity of IgG1/Fc fragments to FcRn at pH 6.0 and their serum t(1/2). To expand this observation, phage display of mutagenized Fc fragments derived from a human IgG1 was used to increase their affinity to both murine and human FcRn. Ten variants were identified that have a higher affinity toward murine and human FcRn at pH 6.0, with DeltaDeltaG (DeltaG(wild type) - DeltaG(mutant)) from 1.0 to 2.0 kcal/mol and from 0.6 to 2.4 kcal/mol, respectively. Those variants exhibit a parallel increase in binding at pH 7.4 to murine, but not human, FcRn. Although not degraded in blood in vitro, accumulated in tissues, nor excreted in urine, their serum concentration in mice is decreased. We propose that higher affinity to FcRn at pH 7.4 adversely affects release into the serum and offsets the benefit of the enhanced binding at pH 6.0.

Animals↗

PubMed2002

Receptor-mediated immunoglobulin G transport across mucosal barriers in adult life: functional expression of FcRn in the mammalian lung.

Mucosal secretions of the human gastrointestinal, respiratory, and genital tracts contain the immunoglobulins (Ig)G and secretory IgA (sIgA) that function together in host defense. Exactly how IgG crosses epithelial barriers to function in mucosal immunity remains unknown. Here, we test the idea that the MHC class I-related Fc-receptor, FcRn, transports IgG across the mucosal surface of the human and mouse lung from lumen to serosa. We find that bronchial epithelial cells of the human, nonhuman primate, and mouse, express FcRn in adult-life, and demonstrate FcRn-dependent absorption of a bioactive Fc-fusion protein across the respiratory epithelium of the mouse in vivo. Thus, IgG, like dimeric IgA, can cross epithelial barriers by receptor-mediated transcytosis in adult animals. These data show that mucosal surfaces that express FcRn reabsorb IgG and explain a mechanism by which IgG may act in immune surveillance to retrieve lumenal antigens for processing in the lamina propria or systemically.

Animals↗

PubMed2002

Compensation for loss of ligand activity in surface plasmon resonance experiments.

The determination of equilibrium binding constants is an important aspect of the analysis of protein-protein interactions. In recent years surface plasmon resonance experiments (e.g., with a BIAcore instrument) have provided a valuable experimental approach to determining such constants. The standard method is based on measuring amounts of analyte bound at equilibrium for different analyte concentrations. During the course of a typical surface plasmon resonance experiment the measured equilibrium levels for a given analyte concentration often decrease. This appears to be due to a loss of activity of the protein coupled to the sensor chip or other phenomena. The loss in signal can lead to an erroneous determination of the equilibrium constant. A data analysis approach is introduced that aims to compensate for the loss of activity so that its influence on the results of the experiments is reduced.

Immunoglobulin Fab Fragments↗

PubMed2002

Expression of the tyrosine phosphatase SRC homology 2 domain-containing protein tyrosine phosphatase 1 determines T cell activation threshold and severity of experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a CD4 Th1-mediated inflammatory demyelinating disorder of the CNS and a well-established animal model for multiple sclerosis. Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) is a cytosolic tyrosine phosphatase that is involved in regulating the T cell activation cascade from signals initiated through the TCR. To study the role of SHP-1 in EAE pathogenesis, we immunized B10.PL mice heterozygous for deletion of the SHP-1 gene (me(v+/-)) and B10.PL wild-type mice with the immunodominant epitope of myelin basic protein (MBP Ac1-11). T cell proliferation and IFN-gamma production were significantly increased in me(v+/-) mice after immunization with MBP Ac1-11. The frequency of MBP Ac1-11-specific CD4 T cells, analyzed by staining with fluorescently labeled tetramers (MBP1-11[4Y]: I-A(u) complexes), was increased in the draining lymph node cells of me(v+/-) mice compared with wild-type mice. In addition, me(v+/-) mice developed a more severe course of EAE with epitope spreading to proteolipid protein peptide 43-64. Finally, expansion of MBP Ac1-11-specific T cells in response to Ag was enhanced in me(v+/-) T cells, particularly at lower Ag concentrations. These data demonstrate that the level of SHP-1 plays an important role in regulating the activation threshold of autoreactive T cells.

Animals↗

PubMed2002

Reversal of tolerance induced by transplantation of skin expressing the immunodominant T cell epitope of rat type II collagen entitles development of collagen-induced arthritis but not graft rejection.

Collagen-induced arthritis (CIA) is induced in H-2(q) mice after immunization with rat type II collagen (CII). The immunodominant T cell epitope on heterologous CII has been located to CII256-270. We have previously shown that TSC transgenic mice, which express the heterologous epitope in type I collagen (CI), e.g. in skin, are tolerized against rat CII and resistant to CIA. In this study we transplanted skin from TSC transgenic mice onto non-transgenic CIA-susceptible littermates to investigate whether introduction of this epitope to a naïve immune system would lead to T cell priming and graft rejection or instead to tolerance and arthritis protection. Interestingly, TSC grafts were accepted and not even immunization of recipient mice with CII in adjuvant induced graft rejection. Instead, TSC skin recipients displayed a reduced T and B cell response to CII and were also protected from arthritis. However, additional priming could break arthritis protection and was accompanied by an increased T cell response to the grafted epitope. Strikingly, despite the regained T cell response, development of arthritis was not accompanied by graft rejection, showing that these immune-mediated inflammatory responses involve different mechanisms.

Age Factors↗

PubMed2002

Achievable accuracy of parameter estimation for multidimensional NMR experiments.

A fundamental issue in NMR spectroscopy is the estimation of parameters such as the Larmor frequencies of nuclei, J coupling constants, and relaxation rates. The Cramer-Rao lower bound provides a method to assess the best achievable accuracy of parameter estimates resulting from an unbiased estimation procedure. We show how the Cramer-Rao lower bound can be calculated for data obtained from multidimensional NMR experiments. The Cramer-Rao lower bound is compared to the variance of parameter estimates for simulated data using a least-squares estimation procedure. It is also shown how our results on the Cramer-Rao lower bound can be used to analyze whether an experimental design can be improved to provide experimental data which can result in parameter estimates with higher accuracy. The concept of nonuniform averaging in the indirect dimension is introduced and studied in connection with nonuniform sampling of the data.

Least-Squares Analysis↗

PubMed2002

Structural snapshot of aberrant antigen presentation linked to autoimmunity: the immunodominant epitope of MBP complexed with I-Au.

Murine experimental allergic encephalomyelitis (EAE) is a useful model for the demyelinating, autoimmune disease multiple sclerosis. In the EAE system, the immunodominant N-terminal epitope of myelin basic protein (MBP) is an unusually short, weakly binding peptide antigen which elicits highly biased TCR chain usage. In the 2.2 A crystal structure of I-A(u)/MBP1-11 complex, only MBP residues 1-7 are bound toward one end of the peptide binding cleft. The fourth residue of MBP1-11 is located in an incompatible p6 pocket of I-A(u), thus explaining the short half-life of I-A(u) complexed with Ac1-11. MBP peptides extended at the C terminus of Ac1-11 result in dramatic affinity increases, likely attributed to register shifting to a higher affinity cryptic epitope, which could potentially mask the presentation of the immunodominant MBP1-11 peptide during thymic education.

Acetylation↗

PubMed2002

Transcytosis and catabolism of antibody.

This review describes the evolution of our knowledge of the transmission of immunoglobulin G (IgG) from mother to infant and the factors which regulate the persistence of IgG in the circulation. These apparently unrelated processes involve the same Fc receptor, FcRn (n = neonatal). FcRn appears to carry out these diverse roles by binding to IgG and then either transporting the bound IgG across cells (transcytosis) or recycling its cargo back to the cell surface (control of catabolism). IgG that is taken up by cells in the absence of binding to FcRn undergoes degradation. Thus, FcRn is the "protective" receptor that serves to maintain IgG homeostasis and deliver IgGs across cellular barriers.

Amino Acid Motifs↗