The CD45 77C/G allele is not associated with myasthenia gravis - a reassessment of the potential role of CD45 in autoimmunity

There was no association between the polymorphism and patient group as a whole (p = 0.199), nor with clinical subgroups. Our results add to a growing number of studies unable to find association between the 77C/G polymorphism and autoimmune disorders. One control sample, from an adult blood donor, was homozygous for the G allele, yet negative for a panel of auto-antibodies, representing the first homozygous individual studied in this respect.The 77C/G mutation does not predispose to MG, and its role in autoimmunity may have to be re-evaluated.Myasthenia gravis (MG) is an autoimmune disorder characterized by the presence of antibodies against the nicotine acetylcholine receptor on the muscle end-plate, thereby impairing transmission of nerve impulses to the muscle. MG occurs in 14/100,000 individuals in Sweden and patients commonly display thymic abnormalities such as thymoma and hyperplasia, where the former usually is associated with a severe disease [1]. Polymorphisms in several "classical" autoimmune genes have previously been shown to be associated with myasthenia gravis, including IL-1, PTPN22 and TNF-α [2]. Furthermore, an association has also been observed with the HLA haplotype A1, B8, DR3 [3-5], known to be linked to several "autoimmune" disorders [6-8].CD45 (PTPRC), located on chromosome 1q31-32, is a receptor belonging to the protein tyrosine phosphatase family, consisting of molecules which have been shown to be involved in cell growth, differentiation and signaling. The receptor is heavily expressed on T-cells, where it comprises up to 10% of all surface proteins [9]. It has previously been shown to play a role in T-cell receptor signal transduction and activation as well as in thymic selection of T-cells, both important features in the development of autoimmunity [9], whereas a lack of CD45 expression results in severe immunodeficiency [10,11]. It undergoes complex, cell specific, alternative splicing to produce eight known isoforms. One isoform, conta