Rheumatoid factor isotypes in rheumatoid arthritis diagnosis and prognosis: a systematic review and meta-analysis

Autoantibodies in rheumatoid arthritis - rheumatoid factor, anticitrullinated protein antibodies and beyond

PURPOSE OF REVIEW

RA is characterized by the presence of autoantibodies among which rheumatoid factors (RFs) and antimodified protein antibodies (AMPA) are serological hallmarks of the disease. In recent years, several novel insights into the biology, immunogenetics and clinical relevance of these autoantibodies have been obtained, which deserve to be discussed in more detail.

RECENT FINDINGS

RFs from RA patients seem to target distinct epitopes which appear to be quite specific for RA. Determination of immunoglobulin A (IgA) isotypes of RF and anticitrullinated protein antibodies (ACPA) may provide prognostic information because their presence is associated with reduced therapeutic responses to TNF inhibitors. Furthermore, IgA levels are increased in RA patients and IgA immune complexes are more potent than immunoglobulin G (IgG) complexes in inducing NET formation. Concerning AMPAs, investigations on variable domain glycosylation (VDG) revealed effects on antigen binding and activation of autoreactive B cells. Studies on pathogenetic involvement of ACPA suggest Janus-faced roles: on the one hand, ACPA may be involved in joint destruction and pain perception while on the other hand protective anti-inflammatory effects may be attributed to a subset of ACPAs.

SUMMARY

The autoimmune response in RA is extremely complex and still far from being fully understood. Antibodies are not only valuable diagnostic biomarkers but also seem to play pivotal roles in the pathophysiology of RA.

From autoantibody test results to decision making: Incorporating likelihood ratios within medical practice

Autoantibodies are important laboratory markers to support diagnosis of autoimmune diseases. Interpretation of autoantibodies is classically done in a dichotomous way (positive versus negative). Yet, interpretation of autoantibody test results can be improved by reporting likelihood ratios. Likelihood ratios convey information on how much more/less likely a test result is in individuals with the disease compared to individuals without the disease. It incorporates information on the antibody level (the higher the antibody level, the higher the association with the disease), which is helpful for (differential) diagnosis. Likelihood ratios are unit-independent and allow users to harmonize test result interpretation. When the likelihood ratio is combined with information on the pre-test probability, post-test probability can be appraised. In this review, the applicability of likelihood ratio in autoimmune diagnostics will be reviewed from the perspective of the clinician, the laboratory professional and the in vitro diagnostic industry.

Evaluation of Dry Eye Severity and Ocular Surface Inflammation in Patients with Autoimmune Rheumatic Diseases

PURPOSE

To evaluate dry eye severity and ocular surface inflammation in autoimmune rheumatic diseases (ARDs).

METHODS

Seventy-nine patients with ARDs were enrolled, including 26 patients with rheumatoid arthritis (RA), 33 patients with systemic lupus erythematosus (SLE), and 20 patients with primary Sjögren's syndrome (pSS). All patients underwent ocular surface evaluations, including ocular surface symptoms, signs, conjunctival impression cytology, and tear multicytokine detection. Systemic conditions, including disease duration, disease activity, and serological parameters, were also noted.

RESULTS

SLE patients had the shortest disease duration, and nearly half of them had low disease activity, while RA patients and pSS patients had a relatively long disease duration, and approximately 90% of them had moderate or high disease activity. The incidence of dry eye and the levels of the proinflammatory tear cytokines in SLE were significantly lower than those in RA and pSS. However, ocular surface squamous metaplasia was more severe in SLE and pSS than in RA. Dry eye severity in all ARD patients was shown to be independent of disease activity, while Nelson's grades were positively correlated with disease duration in RA patients. Disease-related serological parameters were associated with tear proinflammatory cytokines in all ARD patients.

CONCLUSIONS

Variable degrees of dry eye and immune-mediated ocular surface inflammation persist in different ARD patients. In addition to a well-known association between dry eye and pSS, dry eye is also commonly observed in SLE and RA patients. Therefore, there is a definite need for regular ophthalmologic evaluations and topical medications in all patients with ARDs.

Anti-CD64 Antibody-Conjugated PLGA Nanoparticles Containing Methotrexate and Gold for Theranostics Application in Rheumatoid Arthritis

Rheumatoid arthritis, an autoimmune disorder, exerts a considerable effect on quality of life. The inflammatory mechanism involved in rheumatoid arthritis is not clearly known, and therefore the need to develop effective medicines as well as new methods for early detection is a challenge. In this study, we developed PLGA nanoparticles containing gold and methotrexate in core and anti-CD64 antibody conjugated to nanoparticle surface via coupling process. The nanoparticles were examined for their surface morphology using SEM and TEM. The mean particle size, zeta potential, and PDI values of nanoparticles were 413.6 ± 2.89 nm, -10.12 ± 2.12 mV, and 0.23 ± 0.04, respectively, indicating good stability and particle homogeneity. In vitro drug release revealed a controlled release pattern with 93.44 ± 1.60% up to 72 h of release in the presence of pH 5.8, indicating the influence of pH and NIR on drug release. In vivo results on adjuvant-induced arthritis on Wistar rats indicated that animals receiving antibody-conjugated nanoparticles showed improvement in clinical indices and arthritic score as compared to non-conjugated nanoparticles and free drugs. This innovative drug delivery system will be an excellent strategy to maximize therapeutic effectiveness by limiting dosage-related side effects.

Autoantibody-negative rheumatoid arthritis: still a challenge for the rheumatologist

Increased research over the past 30 years has greatly improved the understanding of the pathophysiological mechanisms and clinical aspects of autoantibody-positive rheumatoid arthritis, resulting in improved management and outcomes. In contrast, the subset of rheumatoid arthritis that does not have autoantibodies (such as rheumatoid factor and anti-citrullinated protein autoantibodies) remains less well defined in its pathogenic mechanisms. Autoantibody-negative rheumatoid arthritis continues to pose diagnostic challenges, might respond differently to therapies, and appears to be burdened with different comorbidities and outcomes. The clear separation of rheumatoid arthritis according to serotypes is still a subject of uncertainty and controversy, and studies specifically focused on comparing rheumatoid arthritis and rheumatoid arthritis-like arthritides that do not have autoantibodies remain scarce. The purpose of this Review is to summarise the peculiarities that make autoantibody-negative rheumatoid arthritis different from its autoantibody-positive counterpart, with the aim of generating debate and stimulating further research on this challenging condition.