MHC Class I Presentation of Live and Heat‐Inactivated Sendai Virus Antigen in T2K^b Cells Depends on an Intracellular Compartment with Endosomal Characteristics

Abstract

T2K b cells, which do not express TAP1/2 peptide transporters or the low molecular weight protein 2/7 (LMP2/ 7) proteasomal subunits, can still process and present both live and heat-inactivated Sendai virus (SV). As this operation may also reflect the existence of an alternative processing pathway in normal antigen-presenting cells (APC), the authors have characterized it using intracelluular inhibitors and anti-K b monoclonal antibodies (MoAbs). From the results with lipophilic amines (ammonium chloride, methylamine and chloroquine), cytoskeletal inhibitors (cytochalasin B and vinblastine), and an endoprotease inhibitor (phenylmethylsulfonyl fluoride, PMSF), the authors conclude that the processing of SV antigen in T2K b cells has endosomal characteristics depending on cellular activities such as uptake, vesicular transport and intracellular-vesicular proteolysis. In addition, internalized 'empty' K b molecules derived from the T2K b cell surface appeared to be involved in the presentation of SV antigen, as demonstrated by a protocol using a combination of the Golgi inhibitor brefeldin A(BFA) and anti-K b antibodies. The results thus indicate that T2K b cells process SV antigen in an endosomal-like compartment which contain recycling 'empty' K b molecules.

Immature dendritic cells kill ovarian carcinoma cells by a FAS/FASL pathway, enabling them to sensitize tumor-specific CTLs

“…Necrotic ovarian tumor cells were induced by incubating the ovarian tumor cells in a hypotonic solution for 30 min at 37°C and cell death was determined by uptake of Trypan blue solution. The DCs were pretreated with BFA as described in Material and Methods 54. DCs + apoptotic cell, DCs cocultured with apoptotic autologous ovarian tumor cells for 24 hr as stimulators; DCs + tumor cells, DCs cocultured with untreated live ovarian tumor cells for 48 hr as stimulator; DCs + necrotic cells, DCs cocultured with necrotic ovarian tumor cells for 24 hr.…”

Post-Endoplasmic Reticulum Rescue of Unstable MHC Class I Requires Proprotein Convertase PC7

“…First, exogenous applied peptide derivates often used as substrate-based inhibitors reach pPC-containing cell compartments (31). Second, T2 cells and T2 transfectants are able to process and present exogenous peptide substrates from fluid phase by MHC I (32, 33) through a cellular pathway that is apparently independent of TAP, but requires vesicular transport between secretory compartments (34), indicating that such Ag substrates could serve in T2 cell lines as a source for an alternate MHC I presentation pathway independent of cytosol and peptide transporter (35)(36)(37). Most interestingly, studies on TAP-negative APCs suggested that processing of exogenous peptides for presentation by MHC I involves post-Golgi peptide exchange (38).…”

Neutrophils Process Exogenous Bacteria Via an Alternate Class I MHC Processing Pathway for Presentation of Peptides to T Lymphocytes

“…Exogenous Ag can be processed via alternate MHC-I Ag-processing mechanisms, which may involve delivery of exogenous Ag from vacuolar compartments to the cytosol for cytosolic processing (8 -10) or processing wholly within vacuolar compartments without access to the cytosol (i.e., vacuolar alternate MHC-I Ag processing) (11)(12)(13)(14)(15)(16)(17). Particulate Ags, including bacteria, are efficiently processed by macrophages and dendritic cells for MHC-I presentation.…”