scholarly journals Dynamic Tuning of T Cell Reactivity by Self-Peptide–Major Histocompatibility Complex Ligands

2001 ◽  
Vol 193 (10) ◽  
pp. 1179-1188 ◽  
Author(s):  
Phillip Wong ◽  
Gregory M. Barton ◽  
Katherine A. Forbush ◽  
Alexander Y. Rudensky
Keyword(s):  
Major Histocompatibility Complex ◽  
T Cell ◽  
Mhc Class Ii ◽  
T Cell Activation ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Mhc Molecules ◽  
Dynamic Tuning ◽  
Endogenous Peptide ◽  
Histocompatibility Complex

Intrathymic self-peptide–major histocompatibility complex class II (MHC) molecules shape the T cell repertoire through positive and negative selection of immature CD4+CD8+ thymocytes. By analyzing the development of MHC class II–restricted T cell receptor (TCR) transgenic T cells under conditions in which the endogenous peptide repertoire is altered, we show that self-peptide–MHC complexes are also involved in setting T cell activation thresholds. This occurs through changes in the expression level of molecules on thymocytes that influence the sensitivity of TCR signaling. Our results suggest that the endogenous peptide repertoire modulates T cell responsiveness in the thymus in order to enforce tolerance to self-antigens.

scholarly journals Potent T Cell Activation with Dimeric Peptide–Major Histocompatibility Complex Class II Ligand: The Role of CD4 Coreceptor

1998 ◽  
Vol 188 (9) ◽  
pp. 1633-1640 ◽  
Author(s):  
Abdel Rahim A. Hamad ◽  
Sean M. O'Herrin ◽  
Michael S. Lebowitz ◽  
Ananth Srikrishnan ◽  
Joan Bieler ◽  
...  
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
T Cell ◽  
Mhc Class Ii ◽  
T Cell Activation ◽  
Cell Activation ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Histocompatibility Complex

The interaction of the T cell receptor (TCR) with its cognate peptide–major histocompatibility complex (MHC) on the surface of antigen presenting cells (APCs) is a primary event during T cell activation. Here we used a dimeric IEk-MCC molecule to study its capacity to activate antigen-specific T cells and to directly analyze the role of CD4 in physically stabilizing the TCR–MHC interaction. Dimeric IEk-MCC stably binds to specific T cells. In addition, immobilized dimeric IEk-MCC can induce TCR downregulation and activate antigen-specific T cells more efficiently than anti-CD3. The potency of the dimeric IEk-MCC is significantly enhanced in the presence of CD4. However, CD4 does not play any significant role in stabilizing peptide-MHC–TCR interactions as it fails to enhance binding of IEk-MCC to specific T cells or influence peptide-MHC–TCR dissociation rate or TCR downregulation. Moreover, these results indicate that dimerization of peptide-MHC class II using an IgG molecular scaffold significantly increases its binding avidity leading to an enhancement of its stimulatory capacity while maintaining the physiological properties of cognate peptide–MHC complex. These peptide-MHC–IgG chimeras may, therefore, provide a novel approach to modulate antigen-specific T cell responses both in vitro and in vivo.

scholarly journals H2-DMα−/− Mice Show the Importance of Major Histocompatibility Complex–Bound Peptide in Cardiac Allograft Rejection

2000 ◽  
Vol 192 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Nathan J. Felix ◽  
W. June Brickey ◽  
Robert Griffiths ◽  
Jinghua Zhang ◽  
Luc Van Kaer ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
T Cell ◽  
Mhc Class Ii ◽  
Class Ii ◽  
T Cell Response ◽  
Antigenic Peptides ◽  
Major Histocompatibility ◽  
Mhc Molecules ◽  
Histocompatibility Complex

The role played by antigenic peptides bound to major histocompatibility complex (MHC) molecules is evaluated with H2-DMα−/− mice. These mice have predominantly class II–associated invariant chain peptide (CLIP)-, not antigenic peptide–bound, MHC class II. H2-DMα−/− donor heart grafts survived three times longer than wild-type grafts and slightly longer than I-Aβb−/− grafts. Proliferative T cell response was absent, and cytolytic response was reduced against the H2-DMα−/− grafts in vivo. Residual cytolytic T cell and antibody responses against intact MHC class I lead to eventual rejection. Removal of both H2-DMα and β2-microglobulin (β2m) in cardiac grafts lead to greater (8–10 times) graft survival, whereas removal of β2m alone did not have any effect. These results demonstrate the significance of peptide rather than just allogeneic MHC, in eliciting graft rejection.

scholarly journals Exogenous peptides compete for the presentation of endogenous antigens to major histocompatibility complex class II-restricted T cells.

1991 ◽  
Vol 174 (4) ◽  
pp. 945-948 ◽  
Author(s):  
L Adorini ◽  
J Moreno ◽  
F Momburg ◽  
G J Hämmerling ◽  
J C Guéry ◽  
...  
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
T Cell ◽  
Mhc Class Ii ◽  
T Cell Activation ◽  
Cell Activation ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Egg White Lysozyme ◽  
Histocompatibility Complex

Antigen-presenting cells (APC) transfected with a construct encoding the hen egg-white lysozyme (HEL) amino acid sequence 1-80 constitutively present HEL peptides complexed to major histocompatibility complex (MHC) class II molecules to specific T cell hybridomas, indicating that endogenous cellular antigens can be efficiently presented to class II-restricted T cells. Here we show that exogenous peptide competitors added to HEL-transfected APC can inhibit the presentation of endogenous HEL peptides to class II-restricted T cells. The inhibition is specific for the class II molecule binding the competitor peptide, and it affects to the same extent presentation of exogenous or endogenous HEL peptides. These results, demonstrating that an exogenous competitor can inhibit class II-restricted T cell activation induced by endogenous as well as exogenous antigen, suggest lack of strict compartmentalization between endogenous and exogenous pathways of antigen presentation. Since autoreactive T cells may recognize endogenous, as well as exogenous antigens, the results have implications for the treatment of autoimmune diseases by MHC blockade.

scholarly journals CD1 and Major Histocompatibility Complex II Molecules Follow a Different Course during Dendritic Cell Maturation

2003 ◽  
Vol 14 (8) ◽  
pp. 3378-3388 ◽  
Author(s):  
Nicole N. van der Wel ◽  
Masahiko Sugita ◽  
Donna M. Fluitsma ◽  
Xaiochun Cao ◽  
Gerty Schreibelt ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Major Histocompatibility Complex ◽  
Dendritic Cell ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Dendritic Cell Maturation ◽  
Cell Maturation ◽  
Major Histocompatibility ◽  
Mhc Molecules ◽  
Histocompatibility Complex

The maturation of dendritic cells is accompanied by the redistribution of major histocompatibility complex (MHC) class II molecules from the lysosomal MHC class II compartment to the plasma membrane to mediate presentation of peptide antigens. Besides MHC molecules, dendritic cells also express CD1 molecules that mediate presentation of lipid antigens. Herein, we show that in human monocyte-derived dendritic cells, unlike MHC class II, the steady-state distribution of lysosomal CD1b and CD1c isoforms was unperturbed in response to lipopolysaccharide-induced maturation. However, the lysosomes in these cells underwent a dramatic reorganization into electron dense tubules with altered lysosomal protein composition. These structures matured into novel and morphologically unique compartments, here termed mature dendritic cell lysosomes (MDL). Furthermore, we show that upon activation mature dendritic cells do not lose their ability of efficient clathrin-mediated endocytosis as demonstrated for CD1b and transferrin receptor molecules. Thus, the constitutive endocytosis of CD1b molecules and the differential sorting of MHC class II from lysosomes separate peptide- and lipid antigen-presenting molecules during dendritic cell maturation.

scholarly journals Specificity of T cell clones for antigen and autologous major histocompatibility complex products determines specificity for foreign major histocompatibility complex products.

1983 ◽  
Vol 158 (2) ◽  
pp. 428-437 ◽  
Author(s):  
S R Abromson-Leeman ◽  
H Cantor
Keyword(s):  
Major Histocompatibility Complex ◽  
T Cell ◽  
Molecular Mimicry ◽  
Class Ii ◽  
Major Histocompatibility ◽  
T Cell Clones ◽  
Complex Products ◽  
Mhc Molecules ◽  
Histocompatibility Complex ◽  
Cell Clones

We have analyzed a panel of T cell clones that corecognize defined epitopes of the insulin molecule in association with Ia for their patterns of recognition of alloantigens. A striking correlation is observed between recognition of the I-Ab gene product and cow insulin alpha loop and recognition of I-Eu of the PL/J haplotype. These results are consistent with the notion that reactions to foreign major histocompatibility complex (MHC) products reflect molecular mimicry by foreign class II antigens of 'physiologic' complexes formed by autologous class II MHC molecules and antigen.

scholarly journals Immunogenicity and tolerogenicity of self-major histocompatibility complex peptides.

1990 ◽  
Vol 172 (5) ◽  
pp. 1341-1346 ◽  
Author(s):  
G Benichou ◽  
P A Takizawa ◽  
P T Ho ◽  
C C Killion ◽  
C A Olson ◽  
...  
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
T Cell ◽  
Class Ii ◽  
Class I ◽  
Major Histocompatibility ◽  
Autoreactive T Cells ◽  
Mhc Molecules ◽  
Histocompatibility Complex ◽  
Self Tolerance

Mechanisms involved in self-antigen processing and presentation are crucial in understanding the induction of self-tolerance in the thymus. We examined the immunogenicity of determinants from major histocompatibility complex (MHC) molecules that are expressed in the thymus and have tested peptides derived from the polymorphic regions of class I and class II molecules. We found that two peptides corresponding to NH2 termini of the class II alpha and beta chains (Ak alpha 1-18 and Ak beta 1-16) could bind to self-Ak molecules with high affinity and, surprisingly, were immunogenic in that they could elicit strong proliferative T cell responses in B10.A mice (Ak, Ek). Neonatal injection of peptide Ak beta 1-16 resulted in complete unresponsiveness to this peptide at 8 wk of age showing that these T cells were susceptible to tolerance induction. We have also tested certain class I MHC peptides and showed that some can interact efficiently with class II MHC peptides to induce an autoreactive T cell proliferative response. Among these class I peptides is one (Dd 61-85) that has the capacity to bind to self-Ia without being immunogenic, and therefore represents an MHC determinant that had induced thymic self-tolerance. We conclude that some self-MHC molecules can be processed into peptides that can be presented in the context of intact class II molecules at the surface of antigen-presenting cells. Autoreactive T cells recognizing optimally processed self-peptide/MHC complexes are eliminated during development, whereas other potentially autoreactive T cells escape clonal inactivation or deletion. Incomplete tolerance to self-antigens enriches the T cell repertoire despite the fact that such T cells may eventually become involved in autoimmune disease.

scholarly journals The invariant chain is required for intracellular transport and function of major histocompatibility complex class II molecules.

1994 ◽  
Vol 179 (2) ◽  
pp. 681-694 ◽  
Author(s):  
E A Elliott ◽  
J R Drake ◽  
S Amigorena ◽  
J Elsemore ◽  
P Webster ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Intracellular Transport ◽  
Class Ii ◽  
Misfolded Proteins ◽  
Invariant Chain ◽  
Major Histocompatibility ◽  
Mhc Molecules ◽  
Histocompatibility Complex ◽  
And Function

The major histocompatibility complex (MHC) class II-associated invariant chain (Ii) is thought to act as a chaperone that assists class II during folding, assembly, and transport. To define more precisely the role of Ii chain in regulating class II function, we have investigated in detail the biosynthesis, transport, and intracellular distribution of class II molecules in splenocytes from mice bearing a deletion of the Ii gene. As observed previously, the absence of Ii chain caused significant reduction in both class II-restricted antigen presentation and expression of class II molecules at the cell surface because of the intracellular accumulation of alpha and beta chains. Whereas much of the newly synthesized MHC molecules enter a high molecular weight aggregate characteristic of misfolded proteins, most of the alpha and beta chains form dimers and acquire epitopes characteristic of properly folded complexes. Although the complexes do not bind endogenously processed peptides, class II molecules that reach the surface are competent to bind peptides added to the medium, further demonstrating that at least some of the complexes fold properly. Similar to misfolded proteins, however, the alpha and beta chains are poorly terminally glycosylated, suggesting that they fail to reach the Golgi complex. As demonstrated by double label confocal and electron microscope immunocytochemistry, class II molecules were found in a subcompartment of the endoplasmic reticulum and in a population of small nonlysosomal vesicles possibly corresponding to the intermediate compartment or cis-Golgi network. Thus, although alpha and beta chains can fold and form dimers on their own, the absence of Ii chain causes them to be recognized as "misfolded" and retained in the same compartments as bona fide misfolded proteins.

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