Adjuvant polyarthritis. III. Evidence in support of viral etiology

Adjuvant-induced arthritis in rats. Evidence that autoimmunity to homologous collagens types I, II, IX and XI is not involved in the pathogenesis of arthritis

We examined the sera of arthritic outbred Wistar and Sprague-Dawley rats and inbred Fisher 344 and Wistar-Lewis rats for autoantibodies to rat type I, II, IX and XI collagens following the induction of arthritis with mycobacteria (MTB). Although many sera collected over an extended time were assayed in addition to acid eluates of arthritic joints, convincing evidence for autoimmunity to collagen could not be demonstrated. Instead, modest non-specific reactions were observed to collagen, irrelevant proteins, and buffer-treated plastic microtitre wells. In contrast, antibodies to purified protein derivative (PPD) were detected in the sera of rats developing adjuvant-induced arthritis, and antibodies to type II collagen, in the sera and joint eluate of rats developing experimental collagen-induced arthritis. Lastly, delayed-type hypersensitivity responses to collagen could not be detected, nor could adjuvant-induced arthritis be attenuated by soluble collagen injected intravenously before challenge with MTB. We conclude that adjuvant-induced arthritis and experimental collagen-induced arthritis are distinct models of rheumatic disease and that autoimmunity to collagen is neither prevalent in adjuvant-induced arthritis nor necessary for its pathogenesis.

The absence of antibodies to type II collagen in established adjuvant arthritis in rats

Utilizing an adjuvant arthritis model in rats, we examined humoral immunity to collagen and inflammation in animals with active disease and during drug therapy. Humoral immunity to types I or II collagen was not detected in the sera of rats with advanced adjuvant arthritis; this was in marked contrast to rats with type II collagen-induced arthritis which possessed serum antibodies to native and denatured type II collagen. Hind paw edema and bone pathology were monitored as parameters of inflammation. A new investigational drug, Wy-41,770, was most effective in reducing all of these aspects of inflammatory disease while indomethacin, methylprednisolone, and D-penicillamine caused a less significant diminution of only some of these parameters of inflammation. Antibodies to collagen were not detected in the sera of rats treated with the drugs under study. These data demonstrate that adjuvant arthritis can occur in rats in the absence of antibodies to types I or II collagen.

Adjuvant polyarthritis. VII. The role of type II collagen in pathogenesis

The development of immune response in rats directed toward EL4 cells, after the injection of EL4 cells suspended in a saline/oil emulsion, was enhanced by the incorporation of Mycobacterium into the saline/oil emulsion; the incorporation of type II collagen into the saline-acetic acid/oil emulsion in concentrations ranging from 0.5-25 micrograms/ml had no apparent effect on the development of immune response. The incorporation of type II collagen into the saline-acetic acid/oil emulsion at higher concentrations (100 micrograms and 1.0 mg/ml) significantly suppressed both the humoral and the cell-mediated immune response. Pretreatment of rats with the maximal subarthritiogenic dose of complete Freund's adjuvant prevented the development of arthritis in response to a subsequent injection of an arthritogenic dose of the same adjuvant, but had no effect on the development of type II collagen-induced arthritis. These observations suggest that adjuvant arthritis and the type II collagen-induced arthritis are distinctly different diseases.

Adjuvant polyarthritis in rats: is this a satisfactory model for screening anti-arthritic drugs?

The pathological and biochemical features of the polyarthritis in rats induced by Freund's adjuvant are briefly reviewed. The object of this is to highlight recent studies that provide a basis for specifically improving procedures employed in screening the activity and mode of action of anti-inflammatory/antiarthritic drugs--especially those with possible disease modifying activity. Current screening procedures involve the simple measurement of hind-paw or joint swelling. This may not reflect the extent of degradation or systemic changes in arthritis. It is suggested that it is possible to more precisely measure the extent of joint degradation by the following: (1) X-ray monitoring of joints afflicted with the disease, (2) Histological and morphological examination (the latter in alkali cleared--Alizarin stained preparations) of hindlimbs, (3) Quantitative histoenzymic and biochemical analysis of degradative enzymes and inflammatory mediators. Additional to this specific immunological and systemic (blood, liver) changes should be measured in primary screening in recognition that arthritis is a disease not only of joints but involving the immune, hepatic and possibly other organ systems and that these systemic components clearly have effects on joints. Only by a combined analysis of both local joint and systemic changes during drug treatment will it be possible to discriminate new drugs with disease-modifying activity.

Adjuvant polyarthritis. V. Induction by N-acetylmuramyl-L-alanyl-D-isoglutamine, the smallest peptide subunit of bacterial peptidoglycan

N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), an apparently nonimmunogenic bacterial peptidoglycan-derived small peptide, was found to induce a polyarthritis the rat similar to that induced by Freund's complete adjuvant when injected in the form of an oil emulsion. An oil emulsion of its isomer, N-acetylmuramyl-L-alanyl-L-isoglutamine, which unlike MDP has no immunostimulatory activity, failed to induce the disease.