Deletion of Sptlc1 in mice using Mx1-Cre affects BM and spleen. (A) Western blot analysis for the loss of SPTLC1 protein in the Sptlc1^−/− BMCs. (B) Sphingomyelin, ceramide, and hexosylceramide were analyzed by mass spectrometry and normalized to carbon content. The sphingomyelin levels were 38.5 ± 3 and 15 ± 0.4 pmol per microgram of carbon, the total ceramides were 2.5 ± 0.14 and 0.8 ± 0.1 pmol per microgram of carbon, and the hexosylceramides were 2.1 ± 0.09 and 1 ± 0.02 pmol per microgram of carbon in the Sptlc1^+/+ and Sptlc1^−/− BMCs, respectively. The results are from technical triplicates performed on BM cells from 3 mice of each genotype. (C) Representative images of BM tissue isolated from Sptlc1^+/+ and Sptlc1^−/− mice. (D) Wright-Giemsa staining of BMCs from the Sptlc1^+/+ and Sptlc1^−/− mice. 1, RBC; 2, metamyelocyte; and 3, segmented band cell. Scale bar, 50 μm. (E) BM cellularity was determined from 2 femurs on day 3 in the Sptlc1^+/+ and Sptlc1^−/− mice. (F) Myeloid differentiation in BM hematopoietic cells was analyzed by Mac-1 and Gr-1 staining 3 days after poly(I:C) injection (n = 4). (G) The total numbers of Mac-1⁺Gr-1⁺ cells were plotted for the Sptlc1^+/+ and Sptlc1^−/− mice (n = 4). (H) Myeloid differentiation in spleens obtained from Sptlc1^+/+ and Sptlc1^−/− mice was analyzed by Mac-1 and Gr-1 staining (n = 4). (I) The percentage of CD71⁻Ter119⁺ BMCs was plotted for the Sptlc1^+/+ and Sptlc1^−/− mice (n = 4). (J) The total numbers of CD71⁻Ter119⁺ BMCs were plotted for the Sptlc1^+/+ and Sptlc1^−/− mice (n = 4). All graphs are represented as mean ± standard error of the mean (SEM). P < .05 is significant, calculated from the unpaired Student t test. ns, not significant.