The anti-Sm immune response in autoimmunity and cell biology
Section snippets
Detection of anti-Sm antibodies
Anti-Sm antibodies and antibodies against double stranded DNA are common anti-nuclear antibodies (ANAs) found in patients with SLE. The presence of ANAs is one of the 11 parameters used to identify SLE [2]. The presence of at least 4 of the 11 SLE parameters suggests a diagnosis of SLE. The clinical identification of the anti-Sm antibodies and other ANAs usually begins with immunofluorescence staining to identify antibodies that recognize nuclear antigens. This is typically done by indirect
The snRNP particles
The U1–U12 snRNP particles are designated by their snRNA components which range in size from 80 to 260 nucleotides. U1–U6 are the most abundant snRNP particles and U1 and U2 are present in approximately 1×106 copies per nucleus. The U1, U2, U4 and U5 snRNPs share the set of seven common core proteins, B, D1, D2, D3, E, F and G which are the Sm antigens and are designated the Sm class of snRNPs. In addition to the common core proteins each particle has several snRNP specific proteins (Fig. 1a).
The anti-Sm immune response
The anti-Sm autoimmune response is directed against multiple epitopes on the snRNP common core proteins. The B protein is the major antigen followed by the D1 and D2 proteins. The anti-Sm immune response displays the characteristics of a typical antigen driven response. The T cell epitopes supporting the response are specific to the snRNP core proteins and the anti-Sm Abs show evidence of affinity maturation [13], [14]. Because the snRNP particles is a large multi-protein complex, the B and T
Origins of the anti-Sm response
The etiology of lupus is unknown. A large number of genetic factors and several environmental factors are hypothesized as risk factors for the disease [19]. This suggests a variety of different paths can lead to lupus, thus it is a syndrome rather than a specific disease. However, in many lupus patients anti-Sm autoantibodies are generated. This suggests there are some unusual features of the snRNP particles that predispose them to becoming autoantigens in SLE. Comparisons with other
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Anti-Sm antibodies in the classification criteria of systemic lupus erythematosus
2022, Journal of Translational AutoimmunityCitation Excerpt :The Sm antigen represents not a single protein but a protein complex consisting of a group of core proteins. So far several proteins, being SmB1 (SmB), SmB2 (SmB’), SmB3 (SmN), SmD1, SmD2, SmD3, SmE, SmF and SmG, have been identified, which are expressed in the nuclei of all cells [8]. The Sm proteins, together with ribonucleoproteins and small nuclear RNA (snRNA) form a RNA-protein complex or small nuclear ribonucleoprotein (snRNP), which is involved in precursor messenger RNA (mRNA) splicing, a process which ultimately leads to mature mRNA generation [9].
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