I want to detect the inflammasome formation in THP-1 and RAW macrophages against the treatment of a bacterial toxin. So, is it mandatory to treat these cells with PMA/LPS/Nigercin etc.
The short answer is YES. RAW cell line is defective in ASC expression. Therefore, not good for the ASC inflammasome activation. The treatments you indicated are necessary to detect measurable activity (processing of pro-IL-1beta and pro-IL-18) in THP-1 cells. Without the treatments, basal or constitutive activity is not detectable.
Divaker is correct, particularly for THP-1. However, for a cell line like J774A.1, which have functional inflammasome signaling, you can stimulate with LPS+ATP/Nigiercin/etc without pre-treating with PMA first.
THP-1 cells require PMA treatment because they need to be differentiated from monocytes to macrophages, but J774A.1 cells always display a macrophage-like phenotype.
Does anyone happen to know if PMA is required for inflammasome formation in U937s as well? I would like to keep my cells non-adherent if possible and plan to prime and activate the inflammasome with LPS followed by nigericin.