Differential antigen presentation by heat-treated peripheral blood mononuclear cells and Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL): heated EBV-LCL present alloantigen and soluble antigen but are deficient in the stimulation of autologous EBV-LCL primed T cells

Antigenic properties and processing requirements of 65-kilodalton mannoprotein, a major antigen target of anti-Candida human T-cell response, as disclosed by specific human T-cell clones

T-cell-mediated immunity is known to play a central role in the host response to Candida albicans. T-cell clones are useful tools for the exact identification of fungal T-cell epitopes and the processing requirements of C. albicans antigens. We isolated human T-cell clones from an HLA-DRB1*1101 healthy donor by using an antigenic extract (MP-F2) of the fungus. Specific clones were T-cell receptor alpha/beta and CD4(+)/CD8(-) and showed a T-helper type 1 cytokine profile (production of gamma interferon and not interleukin-4). The large majority of these clones recognized both the natural (highly glycosylated) and the recombinant (nonglycosylated) 65-kDa mannoprotein (MP65), an MP-F2 minor constituent that was confirmed to be an immunodominant antigen of the human T-cell response. Surprisingly, most of the clones recognized two synthetic peptides of different MP65 regions. However, the peptides shared the amino acid motif IXSXIXXL, which may be envisaged as a motif sequence representing the minimal epitope recognized by these clones. Three clones recognized natural and pronase-treated MP65 but did not detect nonglycosylated, recombinant MP65 or the peptides, suggesting a possible role for polysaccharides in T-cell recognition of C. albicans. Finally, lymphoblastoid B-cell lines were efficient antigen-presenting cells (APC) for recombinant MP65 and peptides but failed to present natural, glycosylated antigens, suggesting that nonprofessional APC might be defective in processing highly glycosylated yeast proteins. In conclusion, this study provides the first characterization of C. albicans-specific human T-cell clones and provides new clues for the definition of the cellular immune response against C. albicans.

Effect of in vitro generation of oxygen free radicals on T cell function in young and old rats

T cells from young (6 months) and old (24 months) male Fischer 344 rats were isolated and exposed to three different oxidative stress conditions: (a) reactive oxygen species generated by xanthine-xanthine oxidase (X/XO), (b) hydrogen peroxide (H2O2), and (c) hyperthermia (43 degrees C for 1 h). After oxidative stress treatment, the induction of proliferation and IL-2 production by concanavalin A (Con A) was measured. Exposure of T cells to X/XO or H2O2 resulted in suppression of proliferation and IL-2 expression, and the suppressive effect was more pronounced in T cells from young rats than in T cells from old rats. Similarly, hyperthermia caused inhibition of proliferation and IL-2 expression in T cells from young and old rats. Addition of antioxidant to cultured cells only slightly attenuated the effects of X/XO and H2O2 on T cell function; however, antioxidant had no effect on heat shock-mediated inhibition of proliferation in young or old rats. Because IL-2 plays a crucial role in T cell proliferation and because the transcription factor NFAT (nuclear factor of activated T cell) plays a major role in the regulation of IL-2 transcription, the induction of NFAT as well as NF-KB and AP-1 DNA binding activities in nuclear extracts of the X/XO-treated and untreated control cells was measured using a gel shift assay. The ability of nuclear extracts to bind NFAT or NF-KB oligonucleotide decreased in the X/XO-treated cells from young and old rats compared to the untreated controls. Therefore, these data imply that reactive oxygen species generated by the X/XO system alter the distal step of mitogen-mediated signal transduction, i.e., transcription factors that regulate IL-2 transcription.

Use of Epstein-Barr virus-transformed, autologous B-lymphoblastoid cells as antigen-presenting cells for establishment and maintenance of dengue virus-specific, human cytotoxic T lymphocyte clones

We have been maintaining dengue virus specific CD8+ cytoxic T lymphocyte (CTL) clones by repeated stimulation using autologous peripheral blood mononuclear cells (PBMC) as antigen presenting cells (APCs). In the present study, Epstein-Barr virus (EBV)-transformed autologous lymphoblastoid cell lines (LCL) were compared with autologous PBMC as APCs for long term culture of a dengue virus-specific, HLA class I-restricted CD8+ CTL clone CB2.8. We substituted autologous LCL for autologous PBMC and maintained CB2.8 for several months. CB2.8 cultured using LCL as APCs maintained antigen specific cytolytic activity. No demonstrable difference in the specificity or in the level of cytolytic activity against a panel of target cells was noted between the CB2.8 maintained with LCL and those maintained with PBMC. Lysis of the target cells was blocked by the anti-HLA-class I antibody indicating that HLA class I-restriction was also maintained. We then compared autologous LCL with autologous PBMC in the establishment of CD4 + CTL clones from the PBMC of a dengue-1 immune donor. Dengue 1-specific clones were derived from limiting dilution cultures using either type of APCs. Similar numbers of dengue virus-specific CD4+ CTL clones were established using LCL or PBMC as APCs. These results indicate that autologous LCL act as APCs for long term culture of virus-specific CTL clones and represent a cost effective alternative to repeated collection of PBMC.