scholarly journals Major histocompatibility complex class II compartments in human B lymphoblastoid cells are distinct from early endosomes.

1995 ◽  
Vol 182 (2) ◽  
pp. 325-334 ◽  
Author(s):  
P J Peters ◽  
G Raposo ◽  
J J Neefjes ◽  
V Oorschot ◽  
R L Leijendekker ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Intracellular Distribution ◽  
Endocytic Pathway ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Early Endosomes ◽  
Endocytic Compartments ◽  
Mhc Class Ii Molecules

In human B lymphoblastoid cell lines, the majority of major histocompatibility complex (MHC) class II heterodimers are located on the cell surface and in endocytic compartments, while invariant chain (Ii)-associated class II molecules represent biosynthetic intermediates which are present mostly in the endoplasmic reticulum and Golgi complex. To investigate the origin of the MHC class II-positive compartments and their relation to early endosomes, the intracellular distribution of MHC class II molecules and Ii in relation to endocytic tracers was studied in human lymphoblastoid B cells by immunoelectronmicroscopy on ultrathin cryosections. Cross-linking of surface immunoglobulins, followed by a brief period of internalization of the immune complexes, did not alter the intracellular distribution of MHC class II molecules. While early endosomes were abundantly labeled for the cross-linked immunoglobulins, < 1% of total MHC class II molecules were detectable in early endosomes. MHC class II- and Ii-positive structures associated with the trans-Golgi network can be reached by endocytosed bovine serum albumin (BSA)-gold conjugates after 30 min of internalization. Prolonged exposure to BSA-gold allowed visualization of later endocytic compartments, in which a progressive loss of Ii was observed: first the lumenal portion, and then the cytoplasmic portion of Ii escaped detection, culminating in the formation of MHC class II-positive compartments (MIIC) devoid of Ii. The loss of Ii also correlated with a transition from a multivesicular to a multilaminar, electron-dense MIIC. The intracellular compartments in which class II molecules reside (MIIC) are therefore a heterogeneous set of structures, part of the later aspects of the endocytic pathway.

scholarly journals Relationship between invariant chain expression and major histocompatibility complex class II transport into early and late endocytic compartments.

1993 ◽  
Vol 177 (3) ◽  
pp. 583-596 ◽  
Author(s):  
P Romagnoli ◽  
C Layet ◽  
J Yewdell ◽  
O Bakke ◽  
R N Germain
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Endocytic Pathway ◽  
Invariant Chain ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Endocytic Compartments

Invariant chain (Ii), which associates with major histocompatibility complex (MHC) class II molecules in the endoplasmic reticulum, contains a targeting signal for transport to intracellular vesicles in the endocytic pathway. The characteristics of the target vesicles and the relationship between Ii structure and class II localization in distinct endosomal subcompartments have not been well defined. We demonstrate here that in transiently transfected COS cells expressing high levels of the p31 or p41 forms of Ii, uncleaved Ii is transported to and accumulates in transferrin-accessible (early) endosomes. Coexpressed MHC class II is also found in this same compartment. These early endosomes show altered morphology and a slower rate of content movement to later parts of the endocytic pathway. At more moderate levels of Ii expression, or after removal of a highly conserved region in the cytoplasmic tail of Ii, coexpressed class II molecules are found primarily in vesicles with the characteristics of late endosomes/prelysosomes. The Ii chains in these late endocytic vesicles have undergone proteolytic cleavage in the lumenal region postulated to control MHC class II peptide binding. These data indicate that the association of class II with Ii results in initial movement to early endosomes. At high levels of Ii expression, egress to later endocytic compartments is delayed and class II-Ii complexes accumulate together with endocytosed material. At lower levels of Ii expression, class II-Ii complexes are found primarily in late endosomes/prelysosomes. These data provide evidence that the route of class II transport to the site of antigen processing and loading involves movement through early endosomes to late endosomes/prelysosomes. Our results also reveal an unexpected ability of intact Ii to modify the structure and function of the early endosomal compartment, which may play a role in regulating this processing pathway.

scholarly journals Early Endosomes Are Required for Major Histocompatiblity Complex Class II Transport to Peptide-loading Compartments

1999 ◽  
Vol 10 (9) ◽  
pp. 2891-2904 ◽  
Author(s):  
Valérie Brachet ◽  
Gérard Péhau-Arnaudet ◽  
Catherine Desaymard ◽  
Graça Raposo ◽  
Sebastian Amigorena
Keyword(s):  
Mhc Class Ii ◽  
Class Ii ◽  
Endocytic Pathway ◽  
Cross Linking ◽  
Histocompatibility Complex ◽  
Early Endosomes ◽  
Peptide Loading ◽  
Golgi Network ◽  
Mhc Class Ii Molecules

Antigen presentation to CD4+ T lymphocytes requires transport of newly synthesized major histocompatibility complex (MHC) class II molecules to the endocytic pathway, where peptide loading occurs. This step is mediated by a signal located in the cytoplasmic tail of the MHC class II-associated Ii chain, which directs the MHC class II-Ii complexes from the trans-Golgi network (TGN) to endosomes. The subcellular machinery responsible for the specific targeting of MHC class II molecules to the endocytic pathway, as well as the first compartments these molecules enter after exit from the TGN, remain unclear. We have designed an original experimental approach to selectively analyze this step of MHC class II transport. Newly synthesized MHC class II molecules were caused to accumulate in the Golgi apparatus and TGN by incubating the cells at 19°C, and early endosomes were functionally inactivated by in vivo cross-linking of transferrin (Tf) receptor–containing endosomes using Tf-HRP complexes and the HRP-insoluble substrate diaminobenzidine. Inactivation of Tf-containing endosomes caused a marked delay in Ii chain degradation, peptide loading, and MHC class II transport to the cell surface. Thus, early endosomes appear to be required for delivery of MHC class II molecules to the endocytic pathway. Under cross-linking conditions, most αβIi complexes accumulated in tubules and vesicles devoid of γ-adaptin and/or mannose-6-phosphate receptor, suggesting an AP1-independent pathway for the delivery of newly synthesized MHC class II molecules from the TGN to endosomes.

scholarly journals Engagement of major histocompatibility complex class II molecules by superantigen induces inflammatory cytokine gene expression in human rheumatoid fibroblast-like synoviocytes.

1992 ◽  
Vol 175 (2) ◽  
pp. 613-616 ◽  
Author(s):  
W Mourad ◽  
K Mehindate ◽  
T J Schall ◽  
S R McColl
Keyword(s):  
Gene Expression ◽  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Inflammatory Cytokine ◽  
Class Ii ◽  
Type B ◽  
Major Histocompatibility ◽  
Ifn Gamma ◽  
Histocompatibility Complex ◽  
Mhc Class Ii Molecules

Cells in the rheumatoid synovium express high levels of major histocompatibility complex (MHC) class II molecules in vivo. We have therefore examined the ability of engagement of MHC class II molecules by the superantigen Staphylococcal enterotoxin A (SEA) to activate interleukin 6 (IL-6) and IL-8 gene expression in type B synoviocytes isolated from patients with rheumatoid arthritis. SEA had a minimal or undetectable effect on the expression of either gene in resting synoviocytes, as determined by Northern blot and specific enzyme-linked immunosorbent assay. However, induction of MHC class II molecule expression after treatment of synoviocytes with interferon gamma (IFN-gamma) enabled the cells to respond to SEA in a dose-dependent manner, resulting in an increase in both the level of steady-state mRNA for IL-6 and IL-8, and the release of these cytokines into the supernatant. IFN-gamma by itself had no effect on the expression of either cytokine. Pretreatment of the cells with the transcription inhibitor actinomycin D prevented the increase in cytokine mRNA induced by SEA, whereas cycloheximide superinduced mRNA for both cytokines after stimulation by SEA. Taken together, these results indicate that signaling through MHC class II molecules may represent a novel mechanism by which inflammatory cytokine production is regulated in type B rheumatoid synoviocytes, and potentially provides insight into the manner by which superantigens may initiate and/or propagate autoimmune diseases.

scholarly journals Major histocompatibility complex-restricted recognition of retroviral superantigens by V beta 17+ T cells.

1992 ◽  
Vol 176 (1) ◽  
pp. 275-280 ◽  
Author(s):  
M A Blackman ◽  
F E Lund ◽  
S Surman ◽  
R B Corley ◽  
D L Woodland
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Direct Role ◽  
Histocompatibility Complex ◽  
Class Ii Mhc ◽  
Mhc Class Ii Molecules

It has been established that at least some V beta 17+ T cells interact with an endogenous superantigen encoded by the murine retrovirus, Mtv-9. To analyze the role of major histocompatibility complex (MHC) class II molecules in presenting the Mtv-9 encoded superantigen, vSAG-9 to V beta 17+ hybridomas, a panel of nine hybridomas was tested for their ability to respond to A20/2J (H-2d) and LBK (H-2a) cells which had been transfected with the vSAG-9 gene. Whereas some of the hybridomas recognized vSAG-9 exclusively in the context of H-2a, other hybridomas recognized vSAG-9 exclusively in the context of H-2d or in the context of both H-2d and H-2a. These results suggest that: (a) the class II MHC molecule plays a direct role in the recognition of retroviral superantigen by T cells, rather than serving simply as a platform for presentation; and, (b) it is likely that components of the TCR other than V beta are involved in the vSAG-9/TCR/class II interaction.

scholarly journals Degradation of Mouse Invariant Chain: Roles of Cathepsins S and D and the Influence of Major Histocompatibility Complex Polymorphism

1997 ◽  
Vol 186 (4) ◽  
pp. 549-560 ◽  
Author(s):  
José A. Villadangos ◽  
Richard J. Riese ◽  
Christoph Peters ◽  
Harold A. Chapman ◽  
Hidde L. Ploegh
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Cysteine Proteases ◽  
Class Ii ◽  
Invariant Chain ◽  
Antigenic Peptides ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Antigen Presenting ◽  
Endocytic Compartments

Antigen-presenting cells (APC) degrade endocytosed antigens into peptides that are bound and presented to T cells by major histocompatibility complex (MHC) class II molecules. Class II molecules are delivered to endocytic compartments by the class II accessory molecule invariant chain (Ii), which itself must be eliminated to allow peptide binding. The cellular location of Ii degradation, as well as the enzymology of this event, are important in determining the sets of antigenic peptides that will bind to class II molecules. Here, we show that the cysteine protease cathepsin S acts in a concerted fashion with other cysteine and noncysteine proteases to degrade mouse Ii in a stepwise fashion. Inactivation of cysteine proteases results in incomplete degradation of Ii, but the extent to which peptide loading is blocked by such treatment varies widely among MHC class II allelic products. These observations suggest that, first, class II molecules associated with larger Ii remnants can be converted efficiently to class II–peptide complexes and, second, that most class II–associated peptides can still be generated in cells treated with inhibitors of cysteine proteases. Surprisingly, maturation of MHC class II in mice deficient in cathepsin D is unaffected, showing that this major aspartyl protease is not involved in degradation of Ii or in generation of the bulk of antigenic peptides.

scholarly journals Species-specific binding of CD4 to the beta 2 domain of major histocompatibility complex class II molecules.

1992 ◽  
Vol 175 (4) ◽  
pp. 925-932 ◽  
Author(s):  
D A Vignali ◽  
J Moreno ◽  
D Schiller ◽  
G J Hämmerling
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Peptide Binding ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Species Barrier ◽  
Interaction Sites ◽  
Histocompatibility Complex ◽  
Beta 2 ◽  
Mhc Class Ii Molecules

Exon-shuffled constructs between mouse (IA beta b) and human (DR3 beta) class II beta chains were made to study the interaction sites between CD4 and major histocompatibility complex (MHC) class II molecules, and to determine whether a species barrier is involved. The overall structure and the peptide binding groove appeared to be unaffected by the exon shuffling procedure as determined by monoclonal antibody and peptide binding assays, respectively. While purified CD4+ BALB/c T cells responded strongly in a mixed leukocyte reaction to transfectants expressing the whole IA molecule, the response to IA molecules containing a DR beta 2 domain was substantially reduced. In addition, the presence of an IA beta 2 domain in DR failed to restore the weak xenoreactivity to the whole DR molecule. Similar observations were made with murine HEL-specific, IA alpha k beta b-restricted T cell hybridomas which responded significantly stronger to the whole compared with the exon-shuffled IA molecules. The involvement of CD4 in these differential responses was confirmed by the observation that CD4 loss variants responded to both molecules comparably, and transfection of CD4 into these cells restored the parental phenotype. In contrast, CD4 loss variants transfected with human CD4 responded equally to both the whole and the exon-shuffled molecules. Taken together, these data imply the existence of a partial species barrier, and suggest that CD4 interacts with the beta 2 domain of MHC class II molecules, probably in addition to other contact sites. Models for the interaction of CD4 with MHC class II molecules are presented.

scholarly journals Major Histocompatibility Complex Class II Compartments in Human and Mouse B Lymphoblasts Represent Conventional Endocytic Compartments

1997 ◽  
Vol 139 (3) ◽  
pp. 639-649 ◽  
Author(s):  
Monique J. Kleijmeer ◽  
Stanislaw Morkowski ◽  
Janice M. Griffith ◽  
Alexander Y. Rudensky ◽  
Hans J. Geuze
Keyword(s):  
Major Histocompatibility Complex ◽  
B Cells ◽  
Mhc Class Ii ◽  
Class Ii ◽  
Invariant Chain ◽  
Histocompatibility Complex ◽  
Peptide Complexes ◽  
Endocytic Compartments ◽  
Human And Mouse ◽  
Mhc Class Ii Molecules

In most human and mouse antigen-presenting cells, the majority of intracellular major histocompatibility complex (MHC) class II molecules resides in late endocytic MHC class II compartments (MIICs), thought to function in antigen processing and peptide loading. However, in mouse A20 B cells, early endocytic class II-containing vesicles (CIIVs) have been reported to contain most of the intracellular MHC class II molecules and have also been implicated in formation of MHC class II–peptide complexes. To address this discrepancy, we have studied in great detail the endocytic pathways of both a human (6H5.DM) and a mouse (A20.Ab) B cell line. Using quantitative immunoelectron microscopy on cryosections of cells that had been pulse–chased with transferrin-HRP or BSA-gold as endocytic tracers, we have identified up to six endocytic subcompartments including an early MIIC type enriched in invariant chain, suggesting that it serves as an important entrance to the endocytic pathway for newly synthesized MHC class II/invariant chain complexes. In addition, early MIICs represented the earliest endocytic compartment containing MHC class II– peptide complexes, as shown by using an antibody against an abundant endogenous class II–peptide complex. The early MIIC exhibited several though not all of the characteristics reported for the CIIV and was situated just downstream of early endosomes. We have not encountered any special class II-containing endocytic structures besides those normally present in nonantigen-presenting cells. Our results therefore suggest that B cells use conventional endocytic compartments rather than having developed a unique compartment to accomplish MHC class II presentation.

scholarly journals Distinct Intracellular Compartments Involved in Invariant Chain Degradation and Antigenic Peptide Loading of Major Histocompatibility Complex (MHC) Class II Molecules

1997 ◽  
Vol 139 (6) ◽  
pp. 1433-1446 ◽  
Author(s):  
Giorgio Ferrari ◽  
Andrew M. Knight ◽  
Colin Watts ◽  
Jean Pieters
Keyword(s):  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Human Leukocyte ◽  
Subcellular Location ◽  
Class Ii ◽  
Invariant Chain ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Peptide Loading ◽  
Mhc Class Ii Molecules

Major histocompatibility complex (MHC) class II molecules are transported to intracellular MHC class II compartments via a transient association with the invariant chain (Ii). After removal of the invariant chain, peptides can be loaded onto class II molecules, a process catalyzed by human leukocyte antigen-DM (HLA-DM) molecules. Here we show that MHC class II compartments consist of two physically and functionally distinct organelles. Newly synthesized MHC class II/Ii complexes were targeted to endocytic organelles lacking HLA-DM molecules, where Ii degradation occurred. From these organelles, class II molecules were transported to a distinct organelle containing HLA-DM, in which peptides were loaded onto class II molecules. This latter organelle was not directly accessible via fluid phase endocytosis, suggesting that it is not part of the endosomal pathway. Uptake via antigen-specific membrane immunoglobulin resulted however in small amounts of antigen in the HLA-DM positive organelles. From this peptide-loading compartment, class II–peptide complexes were transported to the plasma membrane, in part after transit through endocytic organelles. The existence of two separate compartments, one involved in Ii removal and the other functioning in HLA-DM–dependent peptide loading of class II molecules, may contribute to the efficiency of antigen presentation by the selective recruitment of peptide-receptive MHC class II molecules and HLA-DM to the same subcellular location.

scholarly journals Binding sites for bacterial and endogenous retroviral superantigens can be dissociated on major histocompatibility complex class II molecules.

1994 ◽  
Vol 179 (3) ◽  
pp. 1029-1034 ◽  
Author(s):  
J Thibodeau ◽  
N Labrecque ◽  
F Denis ◽  
B T Huber ◽  
R P Sékaly
Keyword(s):  
T Cells ◽  
Major Histocompatibility Complex ◽  
Mhc Class Ii ◽  
Binding Sites ◽  
Cell Receptor ◽  
Class Ii ◽  
Bacterial Toxins ◽  
Major Histocompatibility ◽  
Histocompatibility Complex ◽  
Mhc Class Ii Molecules

Bacterial and retroviral superantigens (SAGs) interact with major histocompatibility complex (MHC) class II molecules and stimulate T cells upon binding to the V beta portion of the T cell receptor. Whereas both types of molecules exert similar effects on T cells, they have very different primary structures. Amino acids critical for the binding of bacterial toxins to class II molecules have been identified but little is known of the molecular interactions between class II and retroviral SAGs. To determine whether both types of superantigens interact with the same regions of MHC class II molecules, we have generated mutant HLA-DR molecules which have lost the capacity to bind three bacterial toxins (Staphylococcus aureus enterotoxin A [SEA], S. aureus enterotoxin B [SEB], and toxic shock syndrome toxin 1 [TSST-1]). Cells expressing these mutated class II molecules efficiently presented two retroviral SAGs (Mtv-9 and Mtv-7) to T cells while they were unable to present the bacterial SAGs. These results demonstrate that the binding sites for both types of SAGs can be dissociated.

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