L De Rycke

Anti-citrullinated peptide antibodies may occur in patients with psoriatic arthritis

Background: Anti-cyclic citrullinated peptide (anti-CCP) antibodies are considered highly specific markers of rheumatoid arthritis. Despite the high specificity of the test, anti-CCP antibodies have also been observed in psoriatic arthritis. Objective: To determine the frequency of anti-CCP antibodies in psoriatic arthritis and to describe the clinical characteristics of such patients. Methods: Serum samples from 192 patients with psoriatic arthritis were analysed for anti-CCP antibodies. A previously defined cut off point was applied at a specificity level of ⩾98.5% (42 U/ml). Antibodies against pepA and pepB (two synthetic citrullinated peptides) were determined on samples containing anti-CCP antibodies by line immune assay. The swollen joint count and the numbers of affected joints (present or past) were recorded. Clinical features were noted and if available radiographs of hands and feet were scored for erosions. Rheumatoid factor was determined in all samples. Results: Anti-CCP antibodies were found in 15 patients (7.8%); 13 of 15 anti-CCP2 positive samples were also positive for anti-pepA or pepB antibodies. The prevalence of anti-CCP antibodies was higher than expected in view of the highly specific cut off applied in the test. Detailed analysis of the clinical and radiological features makes it improbable that the high prevalence of anti-CCP antibodies resulted solely from concomitant psoriasis and rheumatoid arthritis or from misclassification. Conclusions: Anti-CCP antibodies may be present in patients with psoriatic arthritis. Although some of the present cohort could have had psoriasis with concomitant rheumatoid arthritis, a proportion at least had the typical characteristics of psoriatic arthritis as the primary diagnosis.

The effect of TNFalpha blockade on the antinuclear antibody profile in patients with chronic arthritis: biological and clinical implications

Since the first proof of efficacy of TNFalpha blockade, both the number of patients treated worldwide and the number of indications for treatment with TNFalpha blockers have grown steadily. Surprisingly, the profound immunomodulation induced by anti-TNFalpha therapy is associated with a relatively low incidence of immune-related complications such as lupus-like syndromes and demyelinating disease. This contrasts sharply with the prominent induction of autoantibodies such as antinuclear antibodies (ANA) and anti-dsDNA antibodies during TNFalpha blockade. Although this phenomenon has been recognized for several years, the clinical and biological implications are not yet fully understood. In this review, recent studies analysing the effect of TNFalpha blockade (infliximab and etanercept) on the ANA profile in autoimmune arthritis will be discussed. Taken together, these reports indicate that the prominent ANA and anti-dsDNA autoantibody response is 1) not a pure class effect of TNFalpha blockers, 2) independent of the disease background, 3) largely restricted to the induction of short-term IgM anti-dsDNA antibodies, and 4) not associated with other serological or clinically relevant signs of lupus. Nevertheless, a careful follow-up of patients treated with TNFalpha blockers remains mandatory, including monitoring for lupus-like characteristics.

Elevated levels of CD5+ B cells in spondyloarthritis patients

We recently proposed that spondyloarthritis (SpA) is characterised by primary alterations in the innate rather than the acquired immune system. However, SpA patients develop a strong IgM antinuclear antibody profile upon tumour necrosis factor blockade. The characteristics of these autoantibodies are compatible with natural antibodies originating from ‘innate’ B cells rather than with genuine, pathogenic autoantibodies. As in mice natural autoantibodies are produced by CD5 expressing peritoneal B cells responding to innate immune signals, we aimed to quantify and …

TNFα blockade impairs T cell dependent humoural responses

Tumour necrosis factor α (TNFα) blockade in spondyloarthritis (SpA) induces antibodies specific for double stranded DNA, which is a T cell independent (TI) antigen. As these antibodies were restricted to the IgM isotype and no antibodies to T cell dependent (TD) antigens were induced, we investigated here if TNF blockade impairs the induction and maturation of TD humoural responses. 30 SpA patients (20 treated …