Receptor editing: genetic reprogramming of autoreactive lymphocytes

Immune tolerance breakdown in inborn errors of immunity: Paving the way to novel therapeutic approaches

Up to 25% of the patients with inborn errors of immunity (IEI) also exhibit immunodysregulatory features. The association of immune dysregulation and immunodeficiency may be explained by different mechanisms. The understanding of mechanisms underlying immune dysregulation in IEI has paved the way for the development of targeted treatments. In this review article, we will summarize the mechanisms of immune tolerance breakdown and the targeted therapeutic approaches to immune dysregulation in IEI.

Contribution of secondary Igkappa rearrangement to primary immunoglobulin repertoire diversification

Abs reactive to DNA and DNA/histone complexes are a distinguished characteristic of primary immunoglobulin repertoires in autoimmune B6.MRL-Fas^lpr and MRL/MpJ-Fas^lpr mice. These mice are defective in Fas receptor, which is critical for the apoptosis of autoreactive B cells by an extrinsic pathway. In the present study, we explored the possibility that bone marrow small pre-B and immature B cells from adult B6.MRL-Fas^lpr mice and MRL/MpJ-Fas^lpr mice respectively, which contain autoreactive B-cell antigen receptors (BCR) and manifest autoimmune syndromes, exhibit enhanced receptor editing patterns. Indeed, FAS^lpr pre B and immature B cells were shown to possess more ongoing replacements of non-productive (nP) than productive (P) primary VκJκ rearrangements. Significantly, the P vs nP ratios of these replaced primary rearrangements were 1:2, thus indicating that κ light-chain production appears not to inhibit secondary rearrangements. In addition, we identified multiple atypical rearrangements, such as Vκ cRS (cryptic recombination signals) cleavages. These results suggest that the onset of light chain secondary rearrangements persists similarly as a non-selected mode and independent of BCR autoreactivity during certain developmental windows of bone marrow B cells in lupus-prone mice and control, and leads us to propose the function of secondary, de novo Igκ rearrangements to increase BCR diversity.