Autoimmune or Autoiflammatory? Bad to the Bone

Iannis E Adamopoulos

Disclosures

Int J Clin Rheumatol. 2015;10(1):5-7. 

In This Article

Autoimmune or Autoinflammatory?

JIA, also known as juvenile rheumatoid arthritis (JRA), is the most common form of arthritis in children and adolescents. The word idiopathic, which is derived from the Greek word idio, (Ïδιo = self) denotes spontaneous pathogenicity. Similarly the related rheumatic diseases RA, PsA and AS are refereed as autoimmune diseases where the prefix auto (αÚτό = itself) again denotes spontaneous pathogenicity through the immune system. Despite the variable etiologies contributing to the progression of these diseases early hypotheses concerning the spontaneous pathogenicity and self-inflicting properties of such rheumatic diseases were attributed to the presence of autoantibodies.[1] Initial evidence came from in vivo murine models such as the KRNxNOD murine model where pathological features that emulated human disease (RA) where completely rescued in KRNxNOD mice devoid of B cells.[2] The role of B cells took a prominent role in inflammatory arthritides as these data suggested that a joint-specific disease need not arise from response to a joint-specific antigen but can be precipitated by a breakdown in general mechanisms of self-tolerance resulting in systemic self-reactivity.

Interestingly, systemic JIA (sJIA), a subset of JIA is set apart from all the other forms of JIA due to the markedly distinct pathogenesis, which does not show any association with HLA genes or with autoantibodies. Instead, it is characterized by an uncontrolled activation of phagocytes and aberrant IL-1 and IL-6 secretion. In fact, sJIA shows common features with macrophage activation syndrome (MAS), which involves activation of macrophages and the release a high amount of pro-inflammatory cytokines. Therefore sJIA is appropriately classified as an autoinflammatory disease related to abnormality of the innate immune system.

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