Type 1A diabetes results from autoimmune destruction of pancreatic beta cells. We examined the involvement of TNF-α and IL-1β, as well as of T cells, macrophages and dendritic cells, in the destruction of beta cells in patients with recent-onset type 1 diabetes.

We obtained pancreatic biopsy specimens from six patients with recent-onset type 1 diabetes and analysed these by immunohistochemistry.

T cell infiltration was less common in islets without beta cells (12.5 [0–33.3]%) than in those with beta cells (46.0 [17.4–83.3]%), while macrophages and dendritic cells showed a similar extent of infiltration into islets both with or without beta cells. TNF-α was detected in 25.0 (4.3–46.9)% of macrophages and 11.8 (0–40.0)% of dendritic cells infiltrating the islets in samples from each patient, but not at all in T cells. IL-1β was detected in 1.8 (0–11.3)% of T cells infiltrating the islets with beta cells, while it was found in 19.2 (0–35.3)% of macrophages or 10.7 (0–31.3)% of dendritic cells infiltrating the islets in samples from each patient (all values median [range]).

Macrophages and dendritic cells infiltrate the islets and produce inflammatory cytokines (TNF-α and IL-1β) during the development of type 1A diabetes.