Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 4 uppsatser.

Thesis (Ph.D.)--Medical College of Ohio, 2004. / In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Medical Sciences. Major advisor: Sonia Najjar. Includes abstract. Document formatted into pages: v, 167 p. Bibliography: pages 117-165.

Thesis (Ph. D.)--Medical College of Ohio, 2004. / "In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Medical Sciences." Major advisor: Sonia Najjar. Includes abstract. Document formatted into pages: iv, 181 p. Title from title page of PDF document Includes bibliographical references (p. 123-180).

Thesis (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2005. / Not embargoed. Vita. References located at the end of each chapter.

Regulation of the immune response is mediated, in part, by the action of suppressor T cells (Ts). One intriguing aspect of these cells is the description of T cell suppressor factor (TsF): a soluble analog of the cell that shares many of its properties, such as the ability to bind free antigen (Ag) and suppress an Ag-specific immune response. The exact molecular nature of TsF and the relationship of TsF to Ts are unknown. The immune response to the small, bacterial protein, ferredoxin (Fd), was used as a model system to study TsF. A Fd-specific suppressor cell network has been described in mice that are genetically nonresponsive to this Ag. Previously, a soluble mediator, known as Fd11F, was found in the culture supernatant (SN) of the Ts hybridoma, Fd11. Fd11F possessed both Ag-binding activity and the ability to suppress the anti-Fd Ab response in mice. The TsF-specific monoclonal antibody, B16G, was used for both the recovery of Fd11F-enriched material from SN and its detection by the enzyme-linked immunosorbent assay. ' Further immunochemical, biological, and biochemical characterization of Fd11F was done with emphasis on describing the Ag-binding properties of Fd11F. It was found that Fd11F bound to solid- and liquid-phase Fd, and demonstrated preferential binding to the carrier determinant of the Ag. A spleen cell culture assay was devised which showed that Fd11F suppressed Ab production in a concentration-dependent manner. Additional experiments suggested that the suppressive effect was Ag-specific. The identification of the Ag-binding molecule was attempted by the fractionation of Fd11F-enriched material using high performance gel filtration or preparative SDS-PAGE (run under non-reducing conditions). Using SDS-PAGE, a unique, single polypeptide of about 30k relative molecular mass (Mr) was identified as the Ag-binding moiety of Fd11F. The possible relationship of this moiety to other identified materials is discussed. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

T cell surface antigens are thought to play significant roles in immunological functions. They are involved in cellular interactions and T cell activation and proliferation. Characterization of T cell antigens is important in understanding the molecular machanisms underlying immune responses. The subject of this thesis is to characterize a novel murine T cell surface antigen called YE1/48. YE1/48, defined by two rat monoclonal antibodies YE1/48.10.6 and YE1/32.8.5, is a dimeric glycoprotein with molecular size and charge resembling the murine T cell antigen receptor α/β. It was initially detected at high levels on two T cell lymphomas, EL-4 and MBL-2. In my thesis studies, the YE1/48 antigen was characterized biochemically, a cDNA clone was isolated, and its expression in lymphoid cell populations was determined. The YE1/48 antigen was found to be distinct from the T cell receptor based on direct comparisons of their primary sequences as well as immunological analyses. It is likely a homodimer with similar or identical subunits. No homology with any known proteins could be detected, including the human T cell activation antigen CD28 (T44) which also has a similar dimeric structure as YE1/48. No function of the YE1/48 antigen could be derived from its primary sequence or with the use of the two monoclonal antibodies because the antibodies do not appear to bind to the surface of intact normal T lymphocytes. Some intriguing characteristics of the YE1/48 antigen were observed in the current studies. The YE1/48 antigen belongs to a rare group of type II membrane proteins with orientation of the amino-terminus inside the cell and the carboxy-terminus outside. The YE1/48 gene may have two alleles among different mouse strains and may belong to a multigene family. YE1/48 is expressed at low levels on a wide range of T cells with no restriction to their differentiation stages, and on spleen B cells as well as bone marrow cells. Its expression on lymphocytes is not related to activation or proliferation. However, YE1/48 expression appears to be induced at high levels by Abelson Murine Leukemia Virus-transformation of pre-B cells. Moreover, the epitopes defined by the YE1/48.10.6 and YE1.32.8.5 antibodies seem to be exposed only on three T lymphomas but not on normal T cells. It is thus tantalizing to speculate a correlation of the high level expression of YE1/48 antigen and its epitope exposure on transformed lymphocytes with cellular transformation. In summary, YE1/48 was found to be a novel T cell surface antigen which has similar dimeric structure as the murine T cell receptor α/β and human CD28 (T44). It has now been characterized biochemically, molecularly cloned, and its expression on lymphoid cells has been determined. Although the function of YE1/48 antigen remains unknown, a number of intriguing characteristics observed in the current studies have certainly called for further studies on the antigen and the determination of its function. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

T and B-lymphocytes play an important role in an adaptive immune response. Communication between these two cells may result in either a humoral immune response or tolerance. Communication between T and B-lymphocytes involves a number of inducible cell surface molecules on both T and B-lymphocytes. It was the aim of this project to gain a greater understanding of the role of CD40 in the dynamic communication that occurs between naïve T-lymphocytes and resting B-lymphocytes during cognate communication. Because in vivo antigen specific T-lymphocytes are at low frequency, it is difficult to examine antigen-specific naïve T-lymphocytes. Thus, an in vitro system employing naïve antigen-specific T cell receptor (TCR) transgenic T cells and small resting B-lymphocytes that did not express CD40 was devised to examine the role of CD40 in cognate communication between naïve T-lymphocytes and resting B-lymphocytes. Upon recognition of antigen on resting B-lymphocytes that expressed CD40, T-lymphocytes proliferated, expressed the activation antigens CD69 and CD25, and remained responsive to subsequent antigen challenge. In the absence of CD40, resting B-lymphocytes did not induce sustained proliferation or sustained expression of the activation markers CD69 and CD25 on naïve T-lymphocytes, and their recovery was decreased compared to naïve T-lymphocytes that recognized antigen on resting B-lymphocytes that expressed CD40. Naïve T-lymphocytes, however, remained responsive to subsequent antigen challenge after recognition of antigen on resting CD40-/- B-lymphocytes. Recognition of antigen on resting CD40-/- B-lymphocytes also resulted in increased recovery and antigen responsiveness of T-lymphocytes when compared to controls without antigen, The role of CD40 in sustaining activation of naïve T-lymphocytes may be unique to resting B-lymphocytes, since proliferation of naïve T-lymphocytes in response to dendritic cells that did not express CD40 was similar to proliferation of naïve T-lymphocytes in response to dendritic cells that expressed CD40. The mechanism by which CD40 sustained activation of naïve T-lymphocytes was investigated by examining the induction of various costimulatory molecules on resting CD40+/- and CD40-/- B-lymphocytes during cognate interaction with naive T-lymphocytes. Induction of B7-1, upregulation of CD44 and ICAM-1, and sustained but not initial induction of B7-2 required that CD40 be expressed on resting B-lymphocytes. Expression of B7-1 and CD44H was not required for proliferation of naïve T-lymphocytes in response to antigen presented on resting B-lymphocytes. However, sustained expression of B7-2 was crucial for proliferation of naïve T-lymphocytes in response to antigen presented on resting B-lymphocytes.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Virginia, 2008. / Title from title page. Includes bibliographical references. Also available online through Digital Dissertations.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on Sept. 17, 2009). Includes bibliographical references.