Here, we found that Lck-cre-mediated T cell-specific loss of Paxbp1 (abbreviated as Paxbp1 cKO) resulted in thymic atrophy and significant reductions in the numbers of DP cells, CD4+ SP, and CD8+ SP cells in the thymus, and fewer T cells in the periphery. The gene discussed is PAXBP1; the disease is thymus atrophy.