Diabetes Care, Vol 19, Issue 11 1177-1184, Copyright © 1996 by American Diabetes Association
Persistent activation of CD8+ T-cells characterizes prediabetic twins
M Peakman, RD Leslie, L Alviggi, M Hawa and D Vergani
Department of Immunology, King's College School of Medicine and Dentistry, London, U.K.
OBJECTIVE: Elevated circulating levels of activated CD3+ T-cells are
characteristic of type I diabetes at diagnosis, and activated CD8+
(cytotoxic/suppressor) T-cells predominate in the islet infiltrate. The aim
of this study was to examine the peripheral blood of prediabetic and
nondiabetic identical twins of patients with type I diabetes for the
presence of activated CD8+ T-cells and by comparing these groups, analyze
the relationship of such cells to the development of the disease. RESEARCH
DESIGN AND METHODS: In a 10-year prospective study, blood T-cell subsets
(CD3+ total T-cells, CD4+ helper/inducer, and CD8+ cytotoxic/suppressor)
were analyzed for evidence of activation (cell surface expression of
HLA-DR, CD25) in 18 identical twins of patients with type I diabetes, 8 of
whom became diabetic (prediabetic twins), while 10 remained nondiabetic
after at least 8 years of follow-up and are now at low risk for type I
diabetes. Fifteen healthy individuals were studied as control subjects.
RESULTS: At the beginning and during the study, percentage levels of
activated CD3+ HLA-DR+ T-cells were significantly elevated in prediabetic
and low-risk twins compared with control subjects (P < 0.005) but
remained high only in prediabetic twins (P < 0.005). Both prediabetic
and low-risk twins had elevated levels of HLA-DR+ CD4+ T helper cells
compared with control subjects throughout the study (P < 0.001), and
these remained high in both (P < 0.001 and P < 0.05, respectively).
Only prediabetic twins had elevated levels of HLA-DR+ CD8+ T-cells during
the study. These were significantly higher than in control subjects (P <
0.005) and low-risk twins (P < 0.05) and remained persistently elevated
to diagnosis (P < 0.001). Abnormally elevated levels of HLA-DR+ CD8+
T-cells in twins indicate a 50% risk of progression to type I diabetes by
life-table analysis (P = 0.01), with a positive predictive value of 100%,
sensitivity of 50%, and specificity of 100%. Elevated CD25+ T-cell levels
in prediabetic and low-risk twins were less marked and less able to
discriminate between the twin groups. CONCLUSIONS: These results
demonstrate that prediabetes is characterized by persistent elevation of
HLA-DR+ CD8+ T-cells with the same cytotoxic phenotype as cells
predominating in the islet at diagnosis, suggesting that the circulating
cells may have a role in the pathogenesis of islet damage.