Disease-biased and shared characteristics of the immunoglobulin gene repertoires in marginal zone B cell lymphoproliferations.

The B cell receptor immunoglobulin (Ig) gene repertoires of marginal zone (MZ) lymphoproliferations were analyzed in order to obtain insight into their ontogenetic relationships. Our cohort included cases with MZ lymphomas (n = 488), i.e. splenic (SMZL), nodal (NMZL) and extranodal (ENMZL), as well as provisional entities (n = 76), according to the WHO classification. The most striking Ig gene repertoire skewing was observed in SMZL. However, restrictions were also identified in all other MZ lymphomas studied, particularly ENMZL, with significantly different Ig gene distributions depending on the primary site of involvement. Cross-entity comparisons of the MZ Ig sequence dataset with a large dataset of Ig sequences (MZ-related or not; n = 65 837) revealed four major clusters of cases sharing homologous ('public') heavy variable complementarity-determining region 3. These clusters included rearrangements from SMZL, ENMZL (gastric, salivary gland, ocular adnexa), chronic lymphocytic leukemia, but also rheumatoid factors and non-malignant splenic MZ cells. In conclusion, different MZ lymphomas display biased immunogenetic signatures indicating distinct antigen exposure histories. The existence of rare public stereotypes raises the intriguing possibility that common, pathogen-triggered, immune-mediated mechanisms may result in diverse B lymphoproliferations due to targeting versatile progenitor B cells and/or operating in particular microenvironments. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Chronic Lymphocytic Leukemia Patient Clustering Based on Somatic Hypermutation (SHM) Analysis.

Somatic Hypermutation (SHM) load in the immunoglobulin heavy variable (IGHV) gene of the clonotypic B cell receptor immunoglobulin (BcR IG) is one of the most important prognostic markers in CLL, segregating patients into two distinct categories, with contrariwise disease course. Over the last years, immunogenetic studies have identified that ∼30% of CLL patients carry (quasi)identical BcR IG and thus can be assigned to different subsets with distinct clinicobiological profiles. This characterization was achieved by applying rules mainly concerning the diversity of the VH complementarity determining region 3 (CDR3). Following, studies have also identified subset-specific somatic hypermutation further highlighting antigen selection in disease ontogeny and evolution. In this study, an innovative attempt to explore possible associations amongst SHMs in different CLL patients is implemented and also the potential correlations with VH CDR3 stereotypy is examined, leading to a new classification algorithm implicating both SHM and CDR3 patterns. All results are classified to a ground level analysis, focusing on the most frequent SHMs, their paired associated amino acid changes and the formation of subgroups sharing the same VH CDR3 pattern, the latter being used as a similarity metric. In addition, all results are compared to established VH CDR3 patterns of the well-known CLL subsets in order to confirm the validity of our findings.