Anti-collagen antibodies and immune complexes in equine joint diseases

Identifying the immunoglobulin G transporter in equine tissues: A look at the neonatal Fc receptor

The neonatal Fc receptor (FcRn) is the receptor responsible for bidirectional transport of immunoglobulin G (IgG) across cells, maintenance of IgG levels in serum, and assisting with antigen presentation. Unfortunately, little is known about FcRn in horses. Therefore, the objective of this study was to provide fundamental information regarding the location of FcRn in equine tissues. Tissues were collected from six horses of mixed breed, age, and sex immediately following euthanasia. Sampling locations included the respiratory tract, gastrointestinal tract (GIT), other visceral organs, cornea, and synovial membrane of the stifle and carpal joints. Tissues for histological analysis were fixed, cross sectioned, and stained for FcRn. Areas of interest were captured and analyzed with data represented as relative fluorescence (RF) to indicate FcRn abundance. Tissues for qPCR analysis were placed in RNAlater and relative quantification (RQ) of FcRn transcripts (FCGRT) was calculated using the 2-ΔΔCT method, normalized to the geometric mean of three reference genes (ACTB, GADPH, HPRT1). Data were analyzed using the general linear model procedure of SAS. Abundance of FcRn differed between tissue types by immunofluorescence and qPCR analysis (P < 0.01). Joint synovium and respiratory tract tissues had the highest RF, GIT tissues expressed moderate RF, and other visceral organs had the lowest RF. Conversely, liver and kidney tissues had the highest RQ while the stomach and cornea had the lowest RQ. These data lay the foundation for future studies regarding FcRn and IgG in horses and their roles in disease prevention and treatment.

Cellular and humoral immunity in chronic equine laminitis

Chronic equine laminitis causes persistent pain and lameness in affected animals and often necessitates euthanasia when pain management strategies become ineffective. Published studies as well as anecdotal reports suggest that this chronic inflammatory disease is associated with systemic alterations in immune responsiveness, perhaps involving an autoimmune component. We investigated this broad hypothesis by measuring a variety of immune indicators in healthy control horses (CON) and horses with chronic laminitis (LMN). We found that white blood cells from LMN horses produced more IFNγ than did cells from CON horses when stimulated in vitro with polyinosinic-polycytidylic acid [poly(I:C)], possibly due to an elevated number of circulating monocytes. No differences between groups were observed in plasma concentrations of IgG, IgA, IgM, IgE, or rheumatoid factor. Laminar tissue from LMN horses expressed elevated levels of keratinocyte damage-related genes as well as inflammatory cytokines and chemokines, which corresponded with a modest amount of neutrophil infiltration as shown by histological staining of fixed tissue and accumulation of neutrophil elastase protein. Taken together, our results do not support the hypothesis of an autoimmune component in chronic laminitis, although the strong induction of neutrophil chemokines and the presence of tissue neutrophils suggests that this cell type is likely involved in perpetuating the inflammation and tissue damage associated with this disease.

Comparative rheumatology: what can be learnt from naturally occurring musculoskeletal disorders in domestic animals?

Examples of naturally occurring musculoskeletal disorders are extremely common in veterinary species and provide a valuable comparative research resource, which can provide compelling comparative data on the aetiopathogenesis and treatment of many common human musculoskeletal diseases. In particular, orthopaedic diseases are a common morbidity in both dogs and horses. In this review, we give an overview of the common musculoskeletal diseases encountered in these species: for instance, tendon and ligament injuries, arthropathies and stress fractures, as well as an insight into the basic biology of these conditions. In doing so, we aim to demonstrate the similarities and differences between these disorders and similar conditions in man.

Antioxidant capacity and oxidative damage determination in synovial fluid of chronically damaged equine metacarpophalangeal joint

In order to determine oxidative stress in equine joints with degenerative processes, we analyzed synovial fluid (SF) antioxidant capacity and the concentration of oxidative damage biomarkers in healthy and chronically damaged metacarpophalangeal joints. SF samples were collected from joints of thirty 2-5 year-old crossbreed male equine, macroscopically classified at post mortem inspection and later histologically confirmed. The antioxidant capacity was determined measuring uric acid and the concentration of sulfhydryl groups and the total radical trapping antioxidant potential (TRAP). The oxidative damage was determined by assessing malondialdehyde (MDA) and carbonyl protein concentration. TRAP was significantly higher (p < 0.05) in the group with chronic damage (CD). The sulfhydryl groups and concentration of uric acid did not show significant difference between the groups (p > 0.05). Although carbonyl concentration did not show significant difference between groups, it was slightly higher in the group with CD (p = 0.05009). Concentration of MDA did not show significant difference (p > 0.05) between groups. The observed significant increase in TRAP in the group with CD could be related to the participation of components other than protein, sulfhydryl groups, or uric acid coming from degenerating joint tissues. These findings could be helpful for a better understanding of the oxidative stress role in equine joints with chronic degenerative process.

Evaluation of anticollagen type I antibody titers in synovial fluid of both stifle joints and the left shoulder joint of dogs with unilateral cranial cruciate disease

OBJECTIVE

To evaluate anticollagen type I antibodies in synovial fluid of the affected stifle joint, the contralateral stifle joint, and the left shoulder joint of dogs with unilateral cranial cruciate ligament (CrCL) rupture during an extended period of 12 to 18 months.

ANIMALS

13 client-owned dogs with CrCL rupture and 2 sham-operated dogs.

PROCEDURES

All dogs were examined and arthrocentesis of all 3 joints was performed every 6 months after surgery. Synovial fluid samples were tested for anticollagen type I antibodies by use of an ELISA.

RESULTS

Dogs with partial CrCL rupture had higher antibody titers than dogs with complete rupture. Six of 13 dogs ruptured the contralateral CrCL during the study, whereby higher antibody titers were found for the stifle joints than for the shoulder joint. Seronegative dogs or dogs with extremely low antibody titers and 2 dogs with high antibody titers did not sustain a CrCL rupture in the contralateral stifle joint.

CONCLUSIONS AND CLINICAL RELEVANCE

In most dogs that had a CrCL rupture of the contralateral stifle joint, a distinct antibody titer gradient toward the stifle joints was detected, suggesting that there was a local inflammatory process in these joints. However, only a small number of sham-operated dogs were used to calculate the cutoff values used to determine the anticollagen type I antibody titers in these patients. Synovial fluid antibodies against collagen type I alone do not initiate CrCL rupture because not all dogs with high antibody titers sustained a CrCL rupture in the contralateral stifle joint.

Immunoglobulin and peripheral B-lymphocyte concentrations in Fell pony foal syndrome

REASONS FOR PERFORMING STUDY

Fell pony foals are affected by a congenital fatal disease that leads to profound anaemia and immunodeficiency. Previous studies comparing healthy and affected foals have shown normal T-cell populations, but a severe B-lymphopenia.

OBJECTIVES

To measure the levels of individual immunoglobulin subisotypes in normal and affected Fell ponies and correlate these levels with the number of peripheral B-lymphocytes.

METHODS

Serum levels of individual immunoglobulin subisotypes were measured by ELISA and correlated with the number of peripheral B-lymphocytes (measured by flow cytometry).

RESULTS

Affected foals had significantly reduced serum levels of IgM, IgGa, IgGb and IgG(T) that coincided with the normal reduction in maternally derived immunoglobulin in foals and, with the exception of IgGb, correlated strongly with the B-lymphopenia.

CONCLUSIONS

These data suggest that affected foals are unable to produce their own immunoglobulins. Therefore, once maternal immunity has waned, it may be the lack of specific foal-derived immunoglobulin that gives rise to the clinical signs of immunodeficiency.

POTENTIAL RELEVANCE

Measurement of IgM after age 4 weeks may provide a more accessible means of confirming the status of future affected Fell pony foals than the measurement of B-lymphocytes (a technique limited to a few specialist laboratories).

Neoantigens in osteoarthritic cartilage

PURPOSE OF REVIEW

Osteoarthritis has been considered a degenerative disease. However, recent evidence supports involvement of immunologic mechanisms in this pathophysiology: for example, inflammation of synovial tissue is observed in osteoarthritis. In osteoarthritis, the proinflammatory cytokine interleukin-1, which is produced by activated synoviocytes and mononuclear cells and has catabolic effects on chondrocytes, is one of the most involved. The immune reaction would require driving antigens. This review describes autoantigens in osteoarthritis and discusses their roles in triggering and/or perpetuating synovitis and joint cartilage destruction in osteoarthritis.

RECENT FINDINGS

Several autoantigens/autoantibodies have been reported in osteoarthritis, such as the cartilage intermediate layer protein. Furthermore, recent comprehensive proteomic surveillance has revealed that comparable numbers of autoantigens were detected in osteoarthritis and rheumatoid arthritis, and that some of them were recognized predominantly in osteoarthritis rather than in rheumatoid arthritis. In addition, it was revealed that the cartilage intermediate layer protein immunization of mice developed calcification of tendons, thus indicating that autoimmunity modulates functions of target molecules.

SUMMARY

Osteoarthritis-specific autoantigens may drive chronic synovitis and may thereby contribute to production of cytokines to upregulate proteases, which lead to chondrocyte and cartilage damage. In addition, autoimmunity may damage joint components by modulating functions of the target molecules.

Aid to the antemortem diagnosis of Fell pony foal syndrome by the analysis of B lymphocytes

Fell pony foals are affected by a congenital fatal immunodeficiency that commonly leads to anaemia and lymphopenia. Previous work has shown that the foals' circulating subpopulations of CD4 and CD8 T lymphocytes are unaffected. In this study it was shown that the mean population of B lymphocytes in 10 affected foals was less than 10 per cent of that in normal foals.

Prevalence and relevance of antibodies to type-I and -II collagen in synovial fluid of dogs with cranial cruciate ligament damage

OBJECTIVE

To measure and compare synovial fluid antibody titers to type-I and -II collagen in stifle joints with instability caused by complete or partial cranial cruciate ligament (CCL) rupture and joints with osteoarthrosis secondary to other pathologic changes in dogs.

ANIMALS

82 dogs with diseased stifle joints.

PROCEDURE

Synovial fluid samples were collected from 7 dogs with clinically normal stifles (control group) and 82 dogs with diseased joints (50 stifle joints with complete rupture of the CCL, 20 with partial damage of the CCL, and 12 joints with radiographic signs of osteoarthritis secondary to other arthropathies). Synovial fluid samples were tested for autoantibodies to type-I and -II collagen by an ELISA.

RESULTS

In dogs with complete and partial CCL rupture, synovial fluid antibody titers to type-I and -II collagen were significantly increased, compared with control dogs. Forty-eight percent (24/50) of samples from dogs with complete CCL rupture and 35% (7/20) of samples from dogs with partial CCL rupture had antibody titers to type-I collagen that were greater than the mean plus 2 standard deviations of the control group titers. Synovial fluid antibody titers to type-II collagen were high in 40% of the dogs with partial or (8/20) complete (20/50) CCL rupture. Dogs with osteoarthrosis secondary to other pathologic changes had significantly increased synovial fluid antibodies to type-I and -II collagen, compared with control dogs.

CONCLUSION

Increases in autoantibodies to collagen in synovial fluid are not specific for the type of joint disorder. It is unlikely that the anticollagen antibodies play an active role in the initiation of weakening of the CCL.

Measurement of serum and synovial fluid keratan sulphate and antibody to collagen type II in equine osteoarthritis

Keratan sulphate (KS) concentration and anticollagen type II antibody levels were measured in the serum and synovial fluid (SF) of clinically normal horses and horses with osteoarthritis (OA). Serum KS in OA was significantly higher than that in normal horses, while no significant difference was found in KS levels of SF between normal and OA. Assays of antibody to collagen type II showed no significant increase in sera and SF of OA. It was suggested that levels of serum KS would be of value in the pathological detection of OA in the joint, although there was no evidence that the measurable autoimmunity to collagen antigens would reflect the process of OA.