Siblings from a litter of AKR/J inbred mice (from The Jackson Laboratory; Stock No. 000648) were inadvertently outcrossed to an unknown mouse, and then bred together for more than 20 generations to generate a series of senescence prone strains. One of these senescence accelerated mice (SAM) strains, SAMP1, was identified with shortened life span and early signs of senescence (spontaneous amyloidosis, alopecia, and osteoporosis) by Dr. T Takeda (Kyoto University, Kyoto, Japan). SAMP1 mice were then sent to Dr. S Matsumoto (Yakult Central Institute for Microbiological Research, Tokyo, Japan), where mice showing spontaneous skin ulceration were selectively mated together. During a transfer from a conventional to specific pathogen free vivaria, mice lost the early senescence (amyloidosis) and developed a transmural, discontinuous ileitis and mild hepatic inflammation without necrosis. After more than 20 generations of inbreeding, the resulting SAMP1/Yit mice were established. In 1996, SAMP1/Yit mice were then sent to Dr. Fabio Cominelli (University of Virginia School of Medicine, Charlottesville Virginia, USA) where they were bred together for more than 20 generations. The resulting SAMP1/YitFcs mice (originally called SAMP1/YitFc or SAMP1/Fc) retained the high prevalence of spontaneous ileitis but also show unique characteristics compared with the original Japanese strain; incidence of skin lesions inversely correlated with the occurrence of intestinal inflammation, established ileitis as early as 10 weeks of age, chronic ileitis with prominent muscular hypertrophy and focal collagen deposition in inflamed segments, activation of mesenteric lymph node lymphocytes coincident with ileitis progression, high interferon-γ production preceding ileitis onset, and emergence of perianal disease with ulceration and fistulae. SAMP1/YitFcs mice are H-2k; reported to have the entire MHC region on chromosome 17 identical to that of AKR/J mice. In 2009, SAMP1/YitFcs mice were sent from the University of Virginia School of Medicine to The Jackson Laboratory and assigned the strain name SAMP1/YitFcsJ.
