ACTB and systemic lupus erythematosus: Both β-actin and myosin-9 intensities correlated linearly with MP concentrations determined by flow cytometry (data not shown), but while the average raw intensity value of myosin-9 (MYH9) in the HC group was 2.7 times higher (p < 0.0001) than in the SLE group, the β-actin (ACTB) value was only 1.4 times higher (p = 0.014).