The insulin A-chain epitope recognized by human T cells is posttranslationally modified.

The autoimmune process that destroys the insulin-producing pancreatic beta cells in type 1 diabetes (T1D) is targeted at insulin and its precursor, proinsulin. T cells that recognize the proximal A-chain of human insulin were identified recently in the pancreatic lymph nodes of subjects who had T1D. To investigate the specificity of proinsulin-specific T cells in T1D, we isolated human CD4(+) T cell clones to proinsulin from the blood of a donor who had T1D. The clones recognized a naturally processed, HLA DR4-restricted epitope within the first 13 amino acids of the A-chain (A1-13) of human insulin. T cell recognition was dependent on the formation of a vicinal disulfide bond between adjacent cysteine residues at A6 and A7, which did not alter binding of the peptide to HLA DR4. CD4(+) T cell clones that recognized this epitope were isolated from an HLA DR4(+) child with autoantibodies to insulin, and therefore, at risk for T1D, but not from two healthy HLA DR4(+) donors. We define for the first time a novel posttranslational modification that is required for T cell recognition of the insulin A-chain in T1D.

Generation and expansion of regulatory human CD4(+) T-cell clones specific for pancreatic islet autoantigens.

Autoantigen-specific regulatory T cells (Treg) are a potential cell therapy for human autoimmune disease, provided they could be generated in adequate numbers and with stable function. To this end, we determined the feasibility of cloning and expanding human CD4(+) Treg specific for the type 1 diabetes autoantigens, GAD65 and proinsulin. Blood CD4(+) cells stimulated to divide in response to GAD65 (in three healthy individuals) or proinsulin (in one type 1 diabetic) were flow sorted into single cells and cultured on feeder cells in the presence of anti-CD3 monoclonal antibody, IL-2 and IL-4. Clones were expanded over 4-6 weeks and screened for autoantigen-dependent suppression of tetanus toxoid-specific T-cell proliferation. Suppression by Treg clones was then confirmed against autoantigen-specific non-Treg clones. Of a total of 447 clones generated, 98 (21.9%) had autoantigen-dependent suppressor function. Treg clones were anergic but proliferated to autoantigen after addition of IL-2 or in co-culture with stimulated bulk T cells, without loss of suppressor function. Treg clones were stored over liquid N(2), thawed and further expanded over 12 days, whereupon they exhibited decreased suppressor function. Expansion of Treg clones overall was in the order 107-108-fold. Treg clones were not distinguished by markers of conventional CD4(+)CD25(+) Treg and suppressed independently of cell-cell contact but not via known soluble suppressor factors. This study demonstrates that autoantigen-specific CD4(+) Treg clones with potential application as a cell therapy for autoimmune disease can be generated and expanded from human blood.

An efficient method for cloning human autoantigen-specific T cells.

T-cell clones are valuable tools for investigating T-cell specificity in infectious, autoimmune and malignant diseases. T cells specific for clinically-relevant autoantigens are difficult to clone using traditional methods. Here we describe an efficient method for cloning human autoantigen-specific CD4+ T cells pre-labelled with CFSE. Proliferating, antigen-responsive CD4+ cells were identified flow cytometrically by their reduction in CFSE staining and single cells were sorted into separate wells. The conditions (cytokines, mitogens and tissue culture plates) for raising T-cell clones were optimised. Media supplemented with IL-2+IL-4 supported growth of the largest number of antigen-specific clones. Three mitogens, PHA, anti-CD3 and anti-CD3+anti-CD28, each stimulated the growth of similar numbers of antigen-specific clones. Cloning efficiency was similar in flat- and round-bottom plates. Based on these findings, IL-2+IL-4, anti-CD3 and round-bottom plates were used to clone FACS-sorted autoantigen-specific CFSE-labelled CD4+ T cells. Sixty proinsulin- and 47 glutamic acid decarboxylase-specific clones were obtained from six and two donors, respectively. In conclusion, the CFSE-based method is ideal for cloning rare, autoantigen-specific, human CD4+ T cells.

Sex steroids modulate human aortic smooth muscle cell matrix protein deposition and matrix metalloproteinase expression.

Large artery stiffening increases cardiovascular risk and promotes isolated systolic hypertension which is more prevalent in elderly women than men. Variation in sex steroid levels between males and females and throughout life may modulate arterial stiffness. We hypothesized that sex steroids directly influence expression of important structural proteins which determine arterial biomechanical properties. Human aortic smooth muscle cells were incubated with physiological concentrations of 17beta-estradiol, progesterone, 17beta-estradiol and progesterone, or testosterone for 4 weeks. Collagen, elastin, and fibrillin-1 deposition was examined (histochemistry/immunohistochemistry). Gene and protein expression of 2 important matrix metalloproteinases (MMPs), MMPs 2 and 3, regulating matrix turnover was assessed. All sex steroids reduced collagen deposition relative to control (100%). However, the reduction was greater with female sex steroids than testosterone (control, 100%; 17beta-estradiol plus progesterone, 20+/-2%; testosterone 74+/-12%, P<0.001). Female sex steroids increased elastin deposition compared with control (control, 100%; 17beta-estradiol, 540+/-60%; progesterone, 290+/-40%; 17beta-estradiol plus progesterone, 400+/-80%, all P<0.01). The elastin/collagen ratio was >11-fold higher in the presence of 17beta-estradiol and progesterone compared with testosterone. Fibrillin-1 deposition was doubled in the presence of female sex steroids (17beta-estradiol plus progesterone) compared with testosterone (P<0.01). MMP-2 gene and protein expression was unaffected by any sex steroid. Testosterone increased both gene and protein expression of MMP-3 relative to both control and female sex steroids (P<0.01). This may contribute to degradation of elastic matrix proteins. In conclusion, female sex steroids promote an elastic matrix profile, which likely contributes to variation in large artery stiffness observed between sexes and with changes in hormonal status across the lifespan.