Aerosol insulin induces regulatory CD8 gamma delta T cells that prevent murine insulin-dependent diabetes

Abstract

Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with insulin-dependent diabetes mellitus (IDDM). When we administered insulin aerosol to NOD mice after the onset of subclinical disease, pancreatic islet pathology and diabetes incidence were both significantly reduced. Insulin-treated mice had increased circulating antibodies to insulin, absent splenocyte proliferation to the major epitope, insulin B chain amino acids 9-23, which was associated with increased IL-4 and particularly IL-10 secretion, and reduced proliferation to glutamic acid decarboxylase, another islet autoantigen. The ability of splenocytes from insulin-treated mice to suppress the adoptive transfer of diabetes to nondiabetic mice by T cells of diabetic mice was shown to be caused by small numbers of CD8 gamma delta T cells. These findings reveal a novel mechanism for suppressing cell-mediated autoimmune disease. Induction of regulatory CD8 gamma delta T cells by aerosol insulin is a therapeutic strategy with implications for the prevention of human IDDM.

Figure 3

Adoptive transfer of diabetes is suppressed by CD8 γδ T cells induced by aerosol insulin: summary of 11 experiments.

Figure 1

Aerosol insulin induces CD8 T cells that suppress the transfer of diabetes. 6–9-wk-old NOD male mice (n = 16 per group) were injected with pooled splenocytes from recently diabetic 14–19-wk-old females, together with either unfractionated (A) or fractionated (B–E) splenocytes from aerosol insulin– or OVA-treated NOD females, and their incidence of diabetes was subsequently monitored. In the experiment shown, aerosol donor mice had been treated for 10 consecutive days and then weekly from 49 d of age, and were normoglycemic when killed at 156 d of age.

Figure 2

Aerosol insulin induces CD8 γδ T cells that suppress transfer of diabetes. Young male NOD mice were coinjected with “diabetic” splenocytes (2 × 10⁷) and total or fractionated splenic T cells from aerosol-treated mice, as described in the legend to Fig. 1. The numbers of fractionated cells injected were, (A) ∼10⁷ total T cells and, from aerosol insulin mice, ∼10⁷ γδ-depleted T cells or 1.4 × 10⁵ γδ T cells and, (B) from aerosol insulin mice, ∼10⁷ total T cells, 2 × 10⁶ CD8 T cells, 2 × 10⁶ γδ-depleted CD8 T cells, or 1.5 × 10⁵ CD8 γδ⁺ T cells.