INS and type 1 diabetes mellitus: In support of this, it was also noted in these cases, that many islets retain at least some residual β-cells at the time of diabetes onset40,41 and that the proportion of insulin-positive islets showing evidence of even mild inflammation is low (often fewer than 30%).37 Thus, in these older children, type 1 diabetes is manifested symptomatically when significant numbers of β-cells are still present and the extent of insulitis is modest.