Correlations between hematopoietic traits and thymic involution. (A) Correlation between the rate of thymic involution (from Hsu et al²⁰  and available on http://www.webQTL.org) and the proliferative response of LSK cells to TGF-β2 (0.1 ng/mL) in liquid cultures supported by kit ligand, flt3 ligand, and thrombopoietin, expressed as a percent of control cultures without TGF-β2 (from Langer et al²⁵ ). Note that at this concentration in the biphasic TGF-β2 dose response, the net effect is in fact inhibitory (Langer et al²⁵ ). The difference in the effect of TGF-β2 among BXD mice was largest at that concentration, however. (B) Correlation between the rate of thymic involution and the frequency of LSK cells in the bone marrow (from Henckaerts et al²⁴ ). (C) Sort windows used for the analysis of the frequency of LSK cells in the bone marrow of BXD RI mouse strains. (D) Frequency of LSK cells in bone marrow 5 months after neonatal (day 7) thymectomy in C57BL/6 mice (n = 5).