In-vivo assessment of T cell kinetics in individuals at risk for type 1 diabetes.

Abstract

We previously assessed the kinetics of T cell turnover in vivo by labeling cells with 2 H-H2 O over 42days in individuals with type 1 diabetes (T1D) and demonstrated an increased turnover of CD4 memory T cells. We have now tested T cell turnover in individuals at risk for T1D using a 3-4-day labeling protocol with 2 H-glucose. We studied 30relatives with T1D with and without autoantibodies, and 10healthy controls. Peripheral blood mononuclear cells (PBMC) were flow-sorted into T cell subsets of interest; 2 H-DNA enrichment was measured by mass spectrometry and in-vivo turnover was calculated as maximum fractional enrichment of deuterated adenosine (Fmax ). Among CD4+ cells, Fmax was highest in regulatory T cells (Treg ), followed by effector and central memory T cells and lowest in naive cells. Similarly, CD8+ central and effector memory T cells had a higher turnover than CD8+ terminally differentiated effector memory T cells (TEMRA) and CD8+ -naive T cells. Relatives as a group showed significantly increased Treg turnover by Fmax compared to controls (1·733±0·6784% versus 1·062±0·3787%, P=0·004), suggesting pre-existing immune dysfunction within families with T1D. However, there was no significant difference in Fmax between groups according to autoantibody or glucose tolerance status. Repeat testing in 20subjects 1year later demonstrated relatively higher within-subject compared to between-subject variability for the measurement of Fmax in various T cell subsets. The short labeling protocol with 2 H-glucose should be applied in the context of a clinical trial in which the therapy is expected to have large effects on T cell turnover.