Neutropenia-induced feedback regulation is TLR-dependent. (A) Absolute cell numbers in hind limb marrows of C3H/HeJ/TLR2-KO mice. Note that control and neutropenic mice (n = 5, each) are identical. p(LSK, GMP, CMP, and MEP) = NS. (B) Absolute cell numbers in hind limb marrows of C3H/HeJ mice after 8 days of 1A8-induced neutropenia. There are no significant differences in control versus neutropenic mice (n = 5). p(LSK, GMP, CMP, and MEP) = NS. (C) Plasma G-CSF levels in control and neutropenic C3H/N, C3H/HeJ/TLR2-KO, and C3H/HeJ mice. Note the significant increase of G-CSF levels in C3H/N and the insignificant differences in C3H/HeJ mice (n = 5). p(C3H/N) = 0.002; p(C3H/HeJ/TLR2-KO) = NS; p(C3H/HeJ) = NS. (D) Absolute cell numbers calculated to reflect total cell counts in both femora and tibiae of n = 3 C3H/N wild-type mice after treatment with 1A8 for 8 days. Note the significant changes of LSK and GMP. p(LSK) = 0.05; p(GMP) = 0.02; p(CMP) = NS; p(MEP) = NS. (E) Flow cytometric analyses of marrow cells in control and 1A8-treated C3H/HeJ mice. Note equal numbers in control and neutropenic mice.