SIRPA and cancer: Such F1/F2 methods have led to the identification of Sirpa allele from NOD/ShiLtJ as a key component for xenograft acceptance – when NOD/ShiLtJ Sirpa allele was engineered into the very resistant BALB/cJ and C57BL/6J strains, these modified strains could accept and develop human hematopoietic and cancer stem cells (Jinnouchi et al., 2020; Kwong et al., 2014; Strowig et al., 2011).