Expression of the chicken lysozyme transgene and the endogenous c-fms gene during macrophage differentiation. Total RNA was prepared from cells at the indicated days of differentiation and relative mRNA levels were measured by real-time PCR with primers specific for GAPDH as an internal control and clys- and c-fms–specific primers. Transgenic mouse ES cells and embryonic fibroblasts served as a negative control. (A) Chicken lysozyme transgene. (B) Endogenous c-fms gene. The values represent the means and standard deviations of 5 independent experiments.