CRP and rheumatoid arthritis: In this sense and given the ability of VIP to regulate the intensity of the inflammatory process and the immune response, the expression of VPAC1 in RA, associated with the activity of the disease, would reflect the patient's clinical status and complement other serum biomarkers of activity used, such as ESR and C-reactive protein (CRP) (114) which are biased by factors such as the gender and the disease duration (115).