Showing papers by "Mark M. Davis published in 1995"

CD95 (Fas)-dependent elimination of self-reactive B cells upon interaction with CD4 + T cells

Abstract: The recessive mouse mutations lpr and gld create deficiencies in an interacting pair of cell surface molecules, CD95 (Fas/APO-1) and Fas-ligand (FasL), respectively, resulting in autoantibody production resembling human systemic lupus erythematosus. The mechanisms of self-tolerance affected by deficiency in either molecule are not established, but CD95 deficiency both in B cells and in CD4+ T cells recognizing major histocompatibility complex (MHC) class II molecules is required for autoimmunity in lpr mice. Here we track the outcome of in vivo interactions between B cells and CD4+ T cells that recognize a transgene-encoded autoantigen, hen egg lysozyme (HEL), using cells from mice transgenic for immunoglobulin and T-cell receptor (TCR) genes. B cells that had not previously encountered HEL autoantigen (naive cells) were triggered into proliferation and antibody production upon interaction with antigen and HEL-specific CD4+ T cells. By contrast, B cells that had been chronically exposed to HEL during their development and carried desensitized surface immunoglobulin (sIg) antigen receptors (anergic cells) did not produce antibody but instead were eliminated in the presence of HEL-specific CD4+ T cells. CD95-deficient anergic B cells, however, were not eliminated by CD4+ T cells and were triggered to proliferate. These findings identify a novel regulatory step for eliminating autoreactive B cells that seems unique in its dependence on CD95.

Antigen-Specific Development of Primary and Memory T Cells in Vivo

Abstract: The expansion and contraction of specific helper T cells in the draining lymph nodes of normal mice after injection with antigen was followed. T cell receptors from purified primary and memory responder cells had highly restricted junctional regions, indicating antigen-driven selection. Selection for homogeneity in the length of the third complementarity-determining region (CDR3) occurs before selection for some of the characteristic amino acids, indicating the importance of this parameter in T cell receptor recognition. Ultimately, particular T cell receptor sequences come to predominate in the secondary response and others disappear, showing the selective preservation or expansion of specific T cell clones.

Compositions and methods for the detection, quantitation and purification of antigen-specific T cells

Abstract: T cells are specifically labeled according to their antigen receptor by binding of a multimeric binding complex. The complex is prepared with major histocompatibility complex protein subunits having a homogeneous population of peptides bound in the antigen presentation site. The multimeric MHC-antigen complex forms a stable structure with T cells, thereby allowing for the labeling, identification and separation of specific T cells.

T-cell receptor V-region usage and antigen specificity. The cytochrome c model system.

Abstract: Investigations of the I-Ek-restricted, cytochrome c-specific T-cell response in mice show that both T-cell receptor V alpha and V beta CDR3 residues and the use of particular V alpha s and V beta s are necessary for recognition. Data strongly suggest that specific CDR3 residues are important in contacting the peptide. Other experiments indicate that the requirement for V alpha:V beta conservation is not the result of strong TCR-->MHC interactions, as no correlation was found between V beta usage and changes in the alpha-helixes of the I-Ek molecule. It is also apparent that changes in V alpha or V beta usage could be elicited by changes in the side chain size of single amino acids of the antigenic peptides, suggesting that V alpha or V beta conservation is important for peptide recognition, either directly or indirectly. We also show that we can follow the cytochrome c response in vivo even in nontransgenic mice, solely by staining with anti-V region antibodies as well as mAbs directed at the activation markers CD44 and L-selectin.

T-cell recognition of antigen. A process controlled by transient intermolecular interactions.

Abstract: As recently as ten years ago, the nature of the T-cell receptor for antigen was a mystery, as was the precise role of histocompatibility molecules in antigen-presentation to T cells. Although T-cell receptors have now been cloned and crystal structures of MHC/peptide molecules exist, our understanding of the parameters that characterize this interaction and other interactions relevant to T-cell immunity are still unclear. The engineering of soluble forms of proteins that mediate T-cell recognition of antigen has allowed the first measurements of these parameters. Interestingly, many of these interactions are of a transient nature, with very rapid off-rates. These data suggest a model whereby highly reversible intermolecular interactions mediate the cell-cell association. The association of adhesion molecules is probably the first step in the stabilization of a conjugate, because they are more numerous than any antigen-specific interaction, followed later by TCR-MHC engagements. Diffusion within each lipid bilayer should allow the congregation of MHC/TCR interactions at the cell-cell interface, with peptide-specific TCR interactions outcompeting irrelevant interactions. Rapid off-rates for both the antigen-specific and nonspecific interactions may be necessary to maintain reversibility, yet allow a rapid approach to equilibrium and consequent signaling when a specific antigen is present or disengagement when it is not.

Abrogation of the allelic exclusion in a T cell receptor beta chain gene transgenic mouse strain.

Abstract: The expression of endogenous T cell receptor (TcR) β chains in a TcR β chain gene transgenic mouse (TGM) strain was examined. Unlike many other TGM strains reported, a considerable proportion of T cells from the thymus and spleen as well as organ cultured fetal thymus from our TGM express endogenous TCR β chains on their surface. Compatible with this was the elucidation of VDJ rearrangement of endogenous β chain genes by PCR. Three color flowcytometric analysis of thymus cell subpopulations revealed that the expression levels of both endogenous and transgenic TcR β genes are regulated in a maturational stage specific manner. Splenic T cells contained a several fold higher percentage of endogenous TcR β positive cells than thymus cells, suggesting a role of TcR on T cell peripherization. Vβ6 positive cells were deleted in the TGM carrying minor lymphocyte stimulating (Mls)-la antigen, indicating that the endogenous TcR β is functional in terms of transmiting a signal for clonal deletion.

Tracking an Imaginary Monster: Isolating T Cell Receptor Genes

Abstract: Publisher Summary This chapter discusses the importance of the discovery of first T cell receptor gene. By the early 1970s, it was clear that lymphocytes could be subdivided into two categories: B cells that bear cell surface immunoglobulins (Ig) and can be turned into antibody secreting factories; and T cells, a much more mysterious category, that were primarily responsible for phenomena such as delayed type hypersensitivity, B cell “help,” and graft rejection. Both B and T lymphocytes seemed capable of antigen recognition and a particularly sensational aspect of the T cell version was that at least some T cells required both a specific antigen and a particular major histocompatibility cell type simultaneously. A consensus in favor of a one-receptor model was reformed where a single site could recognize both antigen and major histocompatibility cell simultaneously. Also, the virtue of having a gene gives many lines of attack not available to those working the antibody–protein angle.