Analysis of bone marrow chimeras, consisting of reconstituted HPSE-1 WT or HPSE-1-deficient RIP-OVAhi host mice with either HPSE-1 WT or HPSE-1-deficient bone marrow cells, revealed that both radio-resistant hosts and haemopoietic-derived bone marrow cells contribute approximately equally to the diabetes incidence attributed to RIP-OVAhi mice. Here, HPSE is linked to diabetes mellitus.