Bovine and Human Insulin Activate CD8+-Autoreactive CTL Expressing Both Type 1 and Type 2 Cytokines in C57BL/6 Mice

Abstract

CD8+ T cells down-regulate a variety of immune responses. For example, porcine and human insulin do not stimulate Abs in C57BL/6 mice because CD8+ T cells inhibit CD4+ helper T cells. By contrast, bovine insulin induces Ab in C57BL/6 mice, and removal of CD8+ T cells does not alter this response. This raises the question of whether porcine, but not bovine, insulin activates CD8+ T cells or whether both insulins activate CD8+ T cells but CD4+ helper T cells are differentially inhibited by them. In this study, we show that insulin-specific CD8+ CTL can be cultured from C57BL/6 mice primed with either bovine or human insulin in CFA. Thus, exogenous Ags, besides OVA, induce CD8+ CTL when administered in an adjuvant, suggesting this is a typical response. These CTL are H-2Kb restricted and produce IL-5, IL-10, IFN-γ, and small amounts of IL-4, which is distinct from IFN-γ and TNF-α that are typically secreted by virus-specific CTL. Moreover, the CTL primed with either bovine or human insulin recognize an A-chain peptide that is identical to the mouse insulin sequence. That foreign proteins, which are closely related to self-proteins, activated autoreactive, CD8+ T cells in vivo is a novel finding. It raises the possibility that self-reactive CTL may be activated by cross-reacting Ags and once activated they might participate in autoimmunity. These results also suggest that down-regulation of insulin-specific responses by autoreactive CD8+ T cells is most likely due to the differential sensitivity of bovine and human insulin-specific CD4+ T cells.

The Effect of Innate Immunity on Autoimmune Diabetes and the Expression of Toll-Like Receptors on Pancreatic Islets

“…Mice on a B6 genetic background do not normally display any spontaneous anti-insulin T cell reactivity, nor do they develop anti-insulin autoantibodies. Although mice on a B6 background do not normally develop diabetes, they are able to respond to insulin after immunization (37,38), indicating the presence of precursors, which under these circumstances could be stimulated to become pathogenic. However, even under the experimental conditions shown in this study, these mice do not produce insulin autoantibodies (data not shown).…”

Antigenic Epitopes Regulate the Phenotype of CD8+ CTL Primed by Exogenous Antigens

“…Such CTL generated are specifically lytic toward their corresponding target cells. However, no CTL were detected without in vivo Ag priming (14,15,17), after priming with soluble protein, or protein in IFA (30) Although OVA-specific and insulin-specific CD8 ϩ lines are cytolytic, they secreted different cytokines upon stimulation. OVA-CTL produced significant amounts of IFN-␥ and TNF-␣ but no IL-4, IL-5, or IL-10, which represents a Tc1 cytokine profile (Fig.…”

“…Previously, we reported that CTL specific for exogenous proteins were primed in C57BL/6 (B6) mice by OVA (14) or bovine insulin (BINS) (15) in CFA. No CTL were elicited in mice primed with soluble proteins or proteins emulsified in IFA (14).…”

Accumulation of Immunosuppressive CD11b+ Myeloid Cells Correlates with the Failure to Prevent Tumor Growth in the Anterior Chamber of the Eye

“…Infiltration of the eye by immunosuppressive CD11b ϩ myeloid cells may play a role in preventing immune elimination of E.G7-OVA by CD8 ϩ CTL. (27) were grown in standard growth medium (SGM) (RPMI 1640 medium supplemented with 10% FBS, 2 mM L-glutamine, 1 mM sodium pyruvate, 50 M 2-ME, gentamicin, penicillin, and streptomycin) at 37°C in a 5% CO 2 atmosphere. All cell lines were maintained free of mycoplasma.…”