What is the role of humoral response in the pathophysiology of relapsing polychondritis (RP)?

Updated: Dec 06, 2018
  • Author: Nicholas Compton, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

The specificity of autoimmune injury to cartilaginous tissues has led investigators to test the hypothesis that a cartilage-specific autoantibody is central to the pathogenesis of relapsing polychondritis. Various studies find circulating antibodies to cartilage-specific collagen types II, IX, and XI to be present in 30%-70% of patients with relapsing polychondritis. Researchers have found that antibodies to type II collagen are present during acute relapsing polychondritis episodes and that the levels correlate with the severity of the episode. [6]

Treatment with prednisone is associated with a decrease in antibody titers. Antibodies to collagen types I, II, and III are believed to result from cartilage destruction; it has been proposed that antibodies are formed as a primary event in relapsing polychondritis. [6] However, anticollagen type II antibodies are not specific to relapsing polychondritis; they have been identified in other arthritides such as rheumatoid arthritis (RA). The epitope specificity of the antibodies in relapsing polychondritis differs from those in RA, suggesting different mechanisms for formation and pathophysiologic roles.

Autoantibodies to minor cartilage-specific collagens (ie, types IX and XI) have been described. They are more likely to be found in association with antibodies to type II collagen in patients with relapsing polychondritis. Furthermore, levels of antibodies to matrilin 1, an extracellular matrix protein predominantly expressed in tracheal cartilage, were significantly higher in patients with relapsing polychondritis, especially in those with respiratory symptoms, than in patients with Wegener granulomatosis, systemic lupus erythematosus, or RA and in healthy controls. [7]

Most patients with relapsing polychondritis had high titers of antifetal cartilage antibodies during the early acute phase. The antifetal cartilage antibodies were found in 6 of 9 patients and only 4 (1.5%) of 260 patients with RA, exclusively in long-standing disease. [8] A report of relapsing polychondritis in the newborn of a mother with relapsing polychondritis suggests that antibodies crossing the placenta are necessary and sufficient to elicit the entire clinical syndrome.

Using proteomic surveillance to identify ubiquitous cellular proteins in patients with relapsing polychondritis, researchers identified 5 proteins that may be autoantigens. These include (1) tubulin-alpha ubiquitous/6, which, as a family, are main components in microtubules; (2) vimentin, an intermediate filament protein; (3) alpha-enolase; (4) calreticulin, a Ca2+ –binding chaperon indispensable for cardiac development; and (5) colligin-1/2. All but tubulin-alpha have been described as autoantigens in other autoimmune diseases (eg, RA, mixed connective-tissue disease, Behçet disease). Although autoantibodies to tubulin-alpha have been reported in other autoimmune conditions, immunoglobulin G (IgG) antibodies to tubulin-alpha chains are rarely reported and may have diagnostic value in persons with relapsing polychondritis. [9]


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