CSF1 and susceptibility to pneumonia measurement: Nevertheless, results of evaluation of pGM-CSF protein levels in piglet sera and activation of downstream signaling of pGM-CSF in PAMs were consistent with observed reduced levels of intracellular PRRSV-RNA and decreased pneumonia incidence in therapeutic mAb-treated piglets, suggesting that pGM-CSF and its associated effects may protect piglets from PRRSV pathogenic processes.