Moreover, while the infection of proliferating primary BMMs in vitro (Fig 5B) with an MMULV-based control retrovirus reduced the expression of Cd14 compared to untreated BMMs (Fig 5C) the retroviral-mediated overexpression of the mouse SP2 protein in primary BMMs caused a significant increase in Cd14 expression in two independent experiments (Fig 5C). Here, SP2 is linked to infection.