Interestingly, our results show that the LIP level of NOD mice is significantly higher than that of Balb/c mice only in age group II, when all lymphopenia, reduced IL-2 production and decreased CD28 expression occur, but not in age group I, III or IV, which was characterized by only reduced IL-2 production, decreased CD28 expression or lymphopenia (Figure 3A, Figure 3D and Figure 4). This evidence concerns the gene CD28 and lymphopenia.