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J M Arkema

Publications and source records attributed to J M Arkema.

8 recordsLinked to original sources
PubMed1994

Double labelling of major histocompatibility complex molecules and lysosomal protein lamp-1 on human dendritic cells.

In this study, double labelling for major histocompatibility complex (MHC) class I and class II molecules and for MHC molecules and the lysosomal membrane protein lamp-1 on ultrathin cryosections of dendritic cells isolated from human peripheral blood was performed. The plasma membrane proved to be positive for both MHC class I and MHC class II molecules and was labelled for only a very few lamp-1 molecules. MHC class I and MHC class II molecules did not co-localize intracellularly except in some peripherally located vesicles. However, many MHC class II-labelled vesicles were present in a juxtanuclear position but only some of them were co-labelled for lamp-1. These results indicate the presence of a separate, non-lysosomal compartment for class II molecules in dendritic cells.

Antigens, CD↗
PubMed1991

A combined method for both endogenous myeloperoxidase and acid phosphatase cytochemistry as well as immunoperoxidase surface labelling discriminating human peripheral blood-derived dendritic cells and monocytes.

On light microscopical (LM) level dendritic cells (DC) isolated from lymphoid organs can be discriminated from macrophages (M phi) by the presence of acid phosphatase (APh) activity in a spot near the nucleus and constitutional expression of class II antigens. The aim of our study was to investigate whether DC and monocytes (Mo) enriched from human peripheral blood could be discriminated on the electron microscopical (EM) level. Therefore we developed a triple method by which we compared the presence of myeloperoxidase (MPO) containing vesicles, the localization of APh containing vesicles and expression of MHC class II and RFD1 (a DC-associated class II-like antigen) plasma-membrane antigens. DC, functionally characterized as potent stimulators in a MLR, are MPO-negative, whereas Mo show MPO in cytoplasmic granules. Although both DC and Mo show little APh activity at LM level, both types of cells show APh activity at the EM level but at different locations. In DC APh containing vesicles are present in a distinct juxtanuclear area, in contrast to Mo, which show APh activity in lysosomes scattered throughout the whole cytoplasm. Moreover, on both LM and EM level, DC are strongly class II positive, whereas Mo show variable labelling intensity for class II, while RFD1 was only found on DC.

Acid Phosphatase↗
PubMed1991

Localization of class II molecules in storage vesicles, endosomes and lysosomes in human dendritic cells.

Class II molecules are a prerequisite for antigen presentation. We studied whether class II molecules can be found in the endocytic and/or lysosomal route of dendritic cells (DC), which are very potent antigen-presenting cells. Therefore first immunolabelling for HLA-DR alpha chain was applied on ultrathin cryosections of cells of which plasma membrane HLA-DR/DQ molecules were labelled in suspension, followed by incubation with the endocytic marker BSA-gold. Second, immunolabelling for HLA-DR alpha chains was applied on ultrathin cryosections of cells on which enzyme cytochemistry for acid phosphatase (APh) was performed to see whether the class II positive vesicles belong to the lysosomal compartment. Third, this immunolabelling was applied on cryosections of cells pretreated with the protein synthesis inhibitor cycloheximide (CHX) to see whether the class II positive vesicles are derived from biosynthesis. We found limited uptake of BSA-gold into endosomes and lysosomes, some of which also contained endocytozed HLA-DR/DQ. APh and HLA-DR were observed in the same vesicles but also vesicles containing either HLA-DR or APh were found. However, many class II positive vesicles were found, which were apparently not accessible to exogenous molecules. Moreover, the amount of class II positive vesicles decreased after treatment of the cells with CHX, suggesting that these vesicles form part of the biosynthetic route. These results imply that there is a cluster of class II positive vesicles, probably a storage compartment, that has connections with the lysosomal system. The concentration of lysosomes and class II positive vesicles in the juxtanuclear area of DC is probably of crucial importance in the processing of antigens.

Alkaline Phosphatase↗
PubMed1991

Morphological and functional characteristics of rat steady state peritoneal dendritic cells.

Dendritic cells (DC) are present in lymphoid organs and also in many non-lymphoid tissues. In this study, DC in the steady state peritoneal cavity of rats were identified morphologically and functionally. Approximately 1% of the peritoneal cells are DC. On cytocentrifuge preparations these cells had the same characteristics as lymph node and spleen DC: they had an irregular outline, all were strongly MHC class II positive and had acid phosphatase activity in a spot in a juxtanuclear position. Also ultrastructurally, peritoneal DC were similar to DC isolated from lymph node and spleen. Enrichment of peritoneal DC, using overnight culture and a Nycodenz gradient, resulted in a highly purified DC fraction. Functionally, peritoneal DC appeared to be very potent antigen-presenting cells, far more potent than peritoneal macrophages, which had an inhibitory rather than an accessory function.

Acid Phosphatase↗
PubMed1990

Human peripheral blood dendritic cells concentrate in contrast to monocytes intracellular HLA class II molecules in a juxtanuclear position.

The localization of histocompatibility antigens of the HLA-D locus in dendritic cells (DC) and monocytes (Mo) isolated from human peripheral blood was investigated. Functionally DC were characterized by their capacity to act as strong stimulators in an allogeneic mixed leucocyte reaction. In cytospins, DC were differentiated from Mo by dendritic morphology, strong HLA class II and moderate RFD1 expression on the plasma membrane and acid phosphatase activity in a juxtanuclear spot. Ultrathin cryosections showed that DC had a heavily labelled plasma membrane for HLA-D. In addition, these antigens were found in intracellular vesicles predominantly located in the juxtanuclear zone. This pattern of labelling was not seen in Mo. Obviously, DC concentrate intracellular class II antigens in the same area as lysosomal activity. These results may indicate that this juxtanuclear area is a center of antigen processing in DC.

Acid Phosphatase↗