Collagen-induced arthritis (CIA) using the rat was originally described by Trentham et al. (1977). Subsequently, this model has gained widespread acceptance and has proven valuable in the study of autoimmune-mediated polyarthritis. Although the mouse model of CIA is often favored for study because of its well-characterized genetic system and plethora of immune reagents, the rat model possesses a number of features that make it desirable. These include the availability of many CIA-susceptible strains, quicker onset of arthritis, and the fact that induction of CIA in rats does not require complete Freund's adjuvant. As with the mouse model, autoimmune arthritis in the rat is dependent on both a T cell and B cell response to the immunogen CII. However, unlike the mouse model, CIA in the rat can only be induced by immunization with native CII.
Chick or bovine native CII (see Support Protocol 1) 10 mM acetic acid, filter sterilized with 0.2-^m filter Incomplete Freund's adjuvant (IFA; e.g., Difco) Rats (see Background Information)
Virtis high speed homogenizer (optional) 1-ml glass syringes with locking hubs 26-G needles
Additional reagents and equipment for preparing antigen/CFA emulsions (unit 2.4) and intradermal injection of rat (unit 1.6)
1. Dissolve CII at concentrations up to 4 mg/ml in 10 mM acetic acid by stirring overnight at 4°C.
2. Using a Vertis high-speed homogenizer or the emulsification technique described in unit 2.4, emulsify CII solution in an equal volume of IFA.
The use of mycobacteria-containing adjuvants (e.g., complete Freund's adjuvant) is not recommended because complete Freund's adjuvant alone can induce an "adjuvant arthritis" in the rat (Pearson, 1963; unit 15.4). The means used to prepare the emulsion is not important provided the emulsion is stable and not subjected to heat during preparation.
3. Using a glass syringe with a locking hub and a 26-G needle, inject rats intradermally with a volume of CII/CFA emulsion containing 300 ^g of CII, using the loose skin at the base of the tail (unit 1.6).
A total of 0.1 ml of emulsion can be injected at multiple locations at the base of the tail with a 26-G needle. Because IFA does not contain mycobacteria, skin ulceration is an infrequent problem, especially when the amount of emulsion administered per site is kept small. Other sites, such as intrascapular and flank regions, also work well.
4. If desired, 7 days after the primary immunization administer a booster injection containing 100 ^g of CII in IFA (prepared and injected as in steps 1 to 3).
Although not necessary when using high-responder strains (see Background Information), a booster immunization will insure maximum incidence and severity of arthritis when using moderate- or low-responding strains.
5. Assess development of arthritis (Support Protocols 4, 5, and 6) and measure B cell Animal Models (Support Protocol 7) and T cell responses to CII (see Support Protocol 8) if desired. for Autoimmune and
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