quantification-proliferating-human-antigen-specific-cd4-t-cells-using

Quantification of Proliferating Human Antigen-specific CD4<sup>+</sup> T Cells using Carboxyfluorescein Succinimidyl Ester

Described is a simple, in vitro, dye dilution-based method for measuring antigen-specific CD4+ T cell proliferation in human peripheral blood mononuclear ...

St. Vincent's Institute of Medical Research

For a long time, immunologists have believed that classical CD4 and CD8 T cells recognize peptides (referred to as epitopes), derived from protein antigens presented by MHC/HLA class I or II. Over the past 10-15 years, it has become clear that epitopes recognized by CD8, and more recently CD4 T cells, can be formed by protein splicing. Here, we review the discovery of spliced epitopes recognized by tumor-specific human CD8 T cells. We discuss how these epitopes are formed and some of the unusual variants that have been reported. Now, over a decade since the first report, evidence is emerging that spliced CD8 T-cell epitopes are much more common, and potentially much more important, than previously imagined. Recent work has shown that epitopes recognized by CD4 T cells can also be formed by protein splicing. We discuss the recent discovery of spliced CD4 T-cell epitopes and their potential role as targets of autoimmune T-cell responses. Finally, we highlight some of the new questions raised from our growing appreciation of T-cell epitopes formed by peptide splicing.

Shuffling peptides to create T-cell epitopes: does the immune system play cards?

Type 1 diabetes (T1D) is an autoimmune disease in which insulin-producing beta cells, found within the islets of Langerhans in the pancreas, are destroyed by islet-infiltrating T cells. Identifying the antigenic targets of beta-cell reactive T cells is critical to gain insight into the pathogenesis of T1D and develop antigen-specific immunotherapies. Several lines of evidence indicate that insulin is an important target of T cells in T1D. Because many human islet-infiltrating CD4 T cells recognize C-peptide-derived epitopes, we hypothesized that full-length C-peptide (PI), the peptide excised from proinsulin as it is converted to insulin, is a target of CD4 T cells in people with T1D. CD4 T cell responses to full-length C-peptide were detected in the blood of: 14 of 23 (>60%) people with recent-onset T1D, 2 of 15 (>13%) people with long-standing T1D, and 1 of 13 (<8%) HLA-matched people without T1D. C-peptide-specific CD4 T cell clones, isolated from six people with T1D, recognized epitopes from the entire 31 amino acids of C-peptide. Eighty-six percent (19 of 22) of the C-peptide-specific clones were restricted by HLA-DQ8, HLA-DQ2, HLA-DQ8, or HLA-DQ2, HLA alleles strongly associated with risk of T1D. We also found that full-length C-peptide was a much more potent agonist of some CD4 T cell clones than an 18mer peptide encompassing the cognate epitope. Collectively, our findings indicate that proinsulin C-peptide is a key target of autoreactive CD4 T cells in T1D. Hence, full-length C-peptide is a promising candidate for antigen-specific immunotherapy in T1D.

Michelle So

Immunology and Diabetes Unit

St. Vincent's Institute of Medical Research

Quantification of Proliferating Human Antigen-specific CD4⁺ T Cells using Carboxyfluorescein Succinimidyl Ester

Michelle So

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Immunology and Diabetes Unit

St. Vincent's Institute of Medical Research

Quantification of Proliferating Human Antigen-specific CD4+ T Cells using Carboxyfluorescein Succinimidyl Ester

Immunology and Diabetes Unit

Quantification of Proliferating Human Antigen-specific CD4⁺ T Cells using Carboxyfluorescein Succinimidyl Ester