Antigen

About: Antigen is a research topic. Over the lifetime, 170233 publications have been published within this topic receiving 6982342 citations. The topic is also known as: antibody generator & Antigen.

Cross-presentation, dendritic cell subsets, and the generation of immunity to cellular antigens

Abstract: Cross-presentation involves the uptake and processing of exogenous antigens within the major histocompatibility complex (MHC) class I pathway. This process is primarily performed by dendritic cells (DCs), which are not a single cell type but may be divided into several distinct subsets. Those expressing CD8alpha together with CD205, found primarily in the T-cell areas of the spleen and lymph nodes, are the major subset responsible for cross-presenting cellular antigens. This ability is likely to be important for the generation of cytotoxic T-cell immunity to a variety of antigens, particularly those associated with viral infection, tumorigenesis, and DNA vaccination. At present, it is unclear whether the CD8alpha-expressing DC subset captures antigen directly from target cells or obtains it indirectly from intermediary DCs that traffic from peripheral sites. In this review, we examine the molecular basis for cross-presentation, discuss the role of DC subsets, and examine the contribution of this process to immunity, with some emphasis on DNA vaccination.

Establishment of FUT8 knockout Chinese hamster ovary cells: an ideal host cell line for producing completely defucosylated antibodies with enhanced antibody-dependent cellular cytotoxicity.

Abstract: To generate industrially applicable new host cell lines for antibody production with optimizing antibody-dependent cellular cytotoxicity (ADCC) we disrupted both FUT8 alleles in a Chinese hamster ovary (CHO)/DG44 cell line by sequential homologous recombination. FUT8 encodes an alpha-1,6-fucosyltransferase that catalyzes the transfer of fucose from GDP-fucose to N-acetylglucosamine (GlcNAc) in an alpha-1,6 linkage. FUT8(-/-) cell lines have morphology and growth kinetics similar to those of the parent, and produce completely defucosylated recombinant antibodies. FUT8(-/-)-produced chimeric anti-CD20 IgG1 shows the same level of antigen-binding activity and complement-dependent cytotoxicity (CDC) as the FUT8(+/+)-produced, comparable antibody, Rituxan. In contrast, FUT8(-/-)-produced anti-CD20 IgG1 strongly binds to human Fcgamma-receptor IIIa (FcgammaRIIIa) and dramatically enhances ADCC to approximately 100-fold that of Rituxan. Our results demonstrate that FUT8(-/-) cells are ideal host cell lines to stably produce completely defucosylated high-ADCC antibodies with fixed quality and efficacy for therapeutic use.

Host resistance directed selectively against H-2-deficient lymphoma variants. Analysis of the mechanism.

Abstract: Three independent variants with a profound reduction of cell surface H-2 have been selected from the C57BL/6 mouse-derived RBL-5 and EL-4 T lymphomas. After subcutaneous inoculation of low cell doses in syngeneic mice, the H-2- variants failed to grow out, whereas the H-2+ control lines showed progressive growth. No difference in growth rate or cloning efficiency was detectable in tissue culture. The in vivo difference in tumor outgrowth was analyzed in detail for one of the H-2-low lines. The outgrowth difference remained after the H-2-low variant and the control line had been injected subcutaneously in opposite flanks of the same mouse, and it was not dependent upon activity of mature T cells, since the same result was seen in athymic nude mice. The difference was partially sensitive to irradiation of the hosts. When mice were pretreated with anti-asialo GM1 antiserum, known to depress natural killer (NK) cell activity, the difference in outgrowth was abolished, and both the control line and the H-2- variant showed progressive growth in vivo. Experiments comparing the distribution and survival of isotope-prelabeled variant and wild type cells indicated that a rapid elimination of the former took place within 24 h after intravenous injection. These differences in tumor elimination were not seen in mice treated with anti-asialo GM1 antiserum. We conclude that the reduced tumorigenicity of sublines with impaired H-2 expression is largely, if not exclusively due to rapid elimination by NK cells. These findings may reflect an inverse, indirect relation between factors controlling H-2 expression and NK sensitivity. Another possible explanation is that major histocompatibility complex (MHC)-encoded gene products are directly involved in a regulatory signal in the NK cell system. According to this interpretation, immunological selectivity in the NK cell system would be achieved by the failure to recognize self-MHC, irrespective of the presence of foreign antigens, i.e. by detection of no-self rather than of nonself. This may also explain previous observations on H-2-linked hybrid resistance against lymphoid grafts and changes in H-2 phenotypes associated with tumor progression.

Patient HLA class I genotype influences cancer response to checkpoint blockade immunotherapy

Abstract: CD8 + T cell–dependent killing of cancer cells requires efficient presentation of tumor antigens by human leukocyte antigen class I (HLA-I) molecules. However, the extent to which patient-specific HLA-I genotype influences response to anti–programmed cell death protein 1 or anti–cytotoxic T lymphocyte–associated protein 4 is currently unknown. We determined the HLA-I genotype of 1535 advanced cancer patients treated with immune checkpoint blockade (ICB). Maximal heterozygosity at HLA-I loci (“A,” “B,” and “C”) improved overall survival after ICB compared with patients who were homozygous for at least one HLA locus. In two independent melanoma cohorts, patients with the HLA-B44 supertype had extended survival, whereas the HLA-B62 supertype (including HLA-B*15:01) or somatic loss of heterozygosity at HLA-I was associated with poor outcome. Molecular dynamics simulations of HLA-B*15:01 revealed different elements that may impair CD8 + T cell recognition of neoantigens. Our results have important implications for predicting response to ICB and for the design of neoantigen-based therapeutic vaccines.

Induction of a CD8( ) cytotoxic T lymphocyte response by cross-priming requires cognate CD4( ) T cell help

Abstract: Class I-restricted presentation is usually associated with cytoplasmic degradation of cellular proteins and is often considered inaccessible to exogenous antigens. Nonetheless, certain exogenous elements can gain entry into this so-called endogenous pathway by a mechanism termed cross-presentation. This is known to be effective for class I-restricted cytotoxic T lymphocyte (CTL) cross-priming directed against a variety of exogenous tumor, viral, and minor transplantation antigens. The related effect of cross-tolerance can also effectively eliminate responses to selected self components. In both cases, this presentation appears to require the active involvement of a bone marrow-derived antigen presenting cell (APC). Here, we show that CTL induction by cross-priming with cell-associated ovalbumin requires the active involvement of CD4+ helper T cells. Importantly, this CD4+ population is only effective when both the helper and CTL determinants are recognized on the same APC. Moreover, we would argue that the cognitive nature of this event suggests that the CD4+ T cell actively modifies the APC, converting it into an effective stimulator for the successful priming of the CTL precursor.