Reduced iNKT cells numbers in type 1 diabetes patients and their first‐degree relatives

Type 1 diabetes (T1D) is an autoimmune disease that is characterized by the specific destruction of insulin‐producing pancreatic β cells. Invariant natural killer T (iNKT) cells have been associated with development of T1D. Class I MHC‐restricted T cell‐associated molecule (CRTAM) is expressed on activated iNKT, CD8(+), and CD4(+) T cells, and it is associated with the pro‐inflammatory profiles of these cells. Crtam gene expression in CD3(+) lymphocytes from non‐obese diabetic (NOD) mice is associated with T1D onset. However, expression of CRTAM on T cells from patients with T1D has not yet been evaluated. We compared iNKT cell (CD3(+)Vα24(+)Vβ11(+)) numbers and CRTAM expression in a Mexican population with recent‐onset T1D and their first‐degree relatives with control families. Remarkably, we found lower iNKT cell numbers in T1D families, and we identified two iNKT cell populations in some of the families. One iNKT cell population expressed high iTCR levels (iNKT(hi)), whereas another expressed low levels (iNKT(lo)) and also expressed CRTAM. These findings support a probable genetic determinant of iNKT cell numbers and a possible role for these cells in T1D development. This study also suggests that CRTAM identifies recently activated iNKT lymphocytes.