Following tissue injury or
infection, the concentrations of several
plasma proteins are altered substantially. The characteristic pattern of this change is termed the
acute phase response, and can be observed in many different inflammatory situations, including surgical
trauma, injury,
infections, tissue
infarction and several immunologically mediated states such as temporalis
arteritis,
polymyalgia rheumatica and
rheumatoid arthritis. It is often of great clinical value to monitor the
acute phase response in humans but the assays used to measure the acute response in man (e.g., erythrocyte sedimentation rate and
C-reactive protein) is less well suited for experimental studies in the rat. We have instead developed a nephelometric assay for determination of
fibrinogen as a marker of the inflammatory response in rats. The assay was used to monitor the inflammatory response in
type II collagen arthritis in rats. This model involves the induction of severe
polyarthritis and is a widely used animal model for
rheumatoid arthritis (RA).
Fibrinogen concentrations increased from 3.1 g/l before immunization to 10.5 g/l 2 weeks after the immunization, after which they gradually declined towards normal levels. This pattern of
fibrinogen alterations correlated well with the inflammatory phase of the arthritic response. Plasma
fibrinogen may thus represent a rapid and sensitive marker of the
acute phase response in the rat.