CD48^−/− BM microenvironment displays a dysregulation of cytokines. (A) BM supernatant was isolated from 8- to 12-week-old CD48^−/− and WT mice, and using cytokine bead arrays we found a severe decrease in IFNγ and Cxcl9. Other cytokines showed a trend of lower levels in the CD48^−/− BM (supplemental Figure 3). (B) Intracellular IFNγ was examined by flow cytometry in hematopoietic progenitors (KLS). A small but consistent population of IFNγ⁺ progenitors was observed, and the CD48^−/− mice exhibited a smaller population of IFNγ⁺ cells in comparison to WT. (C) CD244 expression was examined in short-term progenitors (SP^neg KLS) with TaqMan real-time PCR. CD244 was found to be 5-fold higher in the CD48^−/− short-term progenitors. SYBR green real-time PCR was used to analyze the CD244 isoforms present in the short-term progenitors (SP^neg KLS) and GAPDH was used as an external control. (D) The Itgb2-Vav-Pak-Erk pathway was examined by flow cytometry to determine whether it was up-regulated in the CD48^−/− hematopoietic progenitors (KLS). The number of Itgb2⁺ cells was slightly increased in the CD48^−/− KLS cells, moreover CD48^−/− cells expressing Itgb2 did so at a higher level. (E) In addition, activation of Pak and Erk, as measured by phosphorylation, was significantly increased in the CD48^−/− KLS cells (2-way ANOVA, P < .05).