Anti-PTPRC Monoclonal antibody, clone SB4-7C3

Monozygotic twins provide a unique opportunity to better understand complex genetic diseases and the relative contribution of heritable factors in shaping the immune system throughout life. Common Variable Immunodeficiency Disorders (CVID) are primary antibody defects displaying wide phenotypic and genetic heterogeneity, with monogenic transmission accounting for only a minority of the cases. Here, we report a pair of monozygotic twins concordant for CVID without a family history of primary immunodeficiency. They featured a remarkably similar profile of clinical manifestations and immunological alterations at diagnosis (established at age 37) and along the subsequent 15 years of follow-up. Interestingly, whole-exome sequencing failed to identify a monogenic cause for CVID, but unraveled a combination of heterozygous variants, with a predicted deleterious impact. These variants were found in genes involved in relevant immunological pathways, such as JUN, PTPRC, TLR1, ICAM1, and JAK3. The potential for combinatorial effects translating into the observed disease phenotype is inferred from their roles in immune pathways, namely in T and B cell activation. The combination of these genetic variants is also likely to impose a significant constraint on environmental influences, resulting in a similar immunological phenotype in both twins, despite exposure to different living conditions. Overall, these cases stress the importance of integrating NGS data with clinical and immunological phenotypes at the single-cell level, as provided by multi-dimensional flow-cytometry, in order to understand the complex genetic landscape underlying the vast majority of patients with CVID, as well as those with other immunodeficiencies.

The 77C-->G polymorphism in exon 4 of CD45 or protein tyrosine phosphatase receptor-type C (PTPRC) has been investigated in families with multiple sclerosis (MS) and in several cohorts of sporadic patients and controls, however, with conflicting results. To better understand the role of this functionally important polymorphism in MS, we investigated the transmission of the 'G' allele from unaffected parents to their affected children in 176 families by using linkage and association statistics. The 'G' allele was transmitted to the affected offspring in five of the seven pedigrees carrying this allele and the TRANSMIT program detected association with a P=0.0342. We conclude that the 77C-->G PTPRC polymorphism is present and preferentially transmitted in a small subgroup (<5%) of MS families, which may only be detected with complementary methods of analysis.