Biased immunoglobulin light chain use in the Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

Distinct groups of autoantigens as drivers of ocular adnexal MALT lymphoma pathogenesis

Chronic B-cell receptor signals incited by cognate antigens are believed to play a crucial role in the pathogenesis of mucosa-associated lymphoid tissue lymphomas. We have explored the immunoglobulin variable regions (IGHV) expressed by 124 ocular adnexal MALT lymphomas (OAML) and tested the in vitro reactivity of recombinant IgM derived from 23 OAMLs. Six of 124 OAMLs (5%) were found to express a high-affinity stereotyped rheumatoid factor. OAMLs have a biased IGHV4-34 usage, which confers intrinsic super auto-antigen reactivity with poly-N-acetyllactosamine (NAL) epitopes, present on cell surface glycoproteins of erythrocytes and B cells. Twenty-one OAMLs (17%) expressed IGHV4-34-encoded B-cell receptors. Five of the 23 recombinant OAML IgMs expressed IGHV4-34, four of which bound to the linear NAL i epitope expressed on B cells but not to the branched NAL I epitope on erythrocytes. One non-IGHV4-34-encoded OAML IgM was also reactive with B cells. Interestingly, three of the 23 OAML IgMs (13%) specifically reacted with proteins of U1-/U-snRNP complexes, which have been implicated as cognate-antigens in various autoimmune diseases such as systemic lupus erythematosus and mixed connective tissue disease. The findings indicate that local autoimmune reactions are instrumental in the pathogenesis of a substantial fraction of OAMLs.

Functional antibodies exhibit light chain coherence

The vertebrate adaptive immune system modifies the genome of individual B cells to encode antibodies that bind particular antigens1. In most mammals, antibodies are composed of heavy and light chains that are generated sequentially by recombination of V, D (for heavy chains), J and C gene segments. Each chain contains three complementarity-determining regions (CDR1-CDR3), which contribute to antigen specificity. Certain heavy and light chains are preferred for particular antigens2-22. Here we consider pairs of B cells that share the same heavy chain V gene and CDRH3 amino acid sequence and were isolated from different donors, also known as public clonotypes23,24. We show that for naive antibodies (those not yet adapted to antigens), the probability that they use the same light chain V gene is around 10%, whereas for memory (functional) antibodies, it is around 80%, even if only one cell per clonotype is used. This property of functional antibodies is a phenomenon that we call light chain coherence. We also observe this phenomenon when similar heavy chains recur within a donor. Thus, although naive antibodies seem to recur by chance, the recurrence of functional antibodies reveals surprising constraint and determinism in the processes of V(D)J recombination and immune selection. For most functional antibodies, the heavy chain determines the light chain.

Expression of combinatorial immunoglobulins in macrophages in the tumor microenvironment

Recent evidence indicates the presence of macrophage subpopulations that express the TCRαβ in chronic inflammatory diseases such as tuberculosis and atherosclerosis and in the tumor microenvironment. Here, we demonstrate that a second subpopulation of macrophages expresses rearranged heavy and light chain immunoglobulins. We identify immunoglobulin expression in human and murine monocytes, in ex vivo differentiated macrophages and macrophages from the tumor microenvironment of five randomly selected distinct human tumor entities. The immunoglobulin heavy and light chains are expressed in a small macrophage subfraction (~3-5%) as combinatorial and individual-specific immune receptors. Using Sanger sequencing and deep sequencing, we routinely find markedly restricted Ig repertoires in monocytes/macrophages compared to normal B cells. Furthermore, we report the complete Ig heavy and light chain sequences of a fully functional immunoglobulin from a single tumor-associated macrophage. These results demonstrate that Ig expression is a defining feature of monocytes and also macrophages in the tumor microenvironment and thus reveal an as yet unrecognized modus operandi of host defense in professional phagocytes.

New human single chain anti-idiotypic antibody against benzo[a]pyrene

The nal¨ve library from the lymphocytes of healthy humans was screened by murine single-stranded idiotypic antibodies against benzo[a]pyrene (pSh). The phage clone which contained of anti-idiotypic antibody against benzo[a]pyrene, designated as A4, was chosen for further work because of highly specific to pSh. The available protein databases were searched. The A4 amino acid sequence was unique and 76% identical to a sequence in antibody against interferon g. The A4 protein was expressed in bacteria and purified by two different methods: His-tagged A4 and CBD-fusion A4. Both the A4 bound to pSh and also to the human single chain idiotypic antibody against the benzo[a]pyrene (T72) by ELISA. The K_d values of A4 for pSh and T72 were very close: 4.44 × 10^-7 M and 5.71 × 10^-7M, respectively. A4 was a competitor with benzo[a]pyrene for binding sites of both idiotypic pSh and T72 in competitive ELISA. Thus, A4 was a high affinity anti-idiotypic against benzo[a]pyrene which recognised pSh and T72 active sites.

The Individual and Population Genetics of Antibody Immunity

Antibodies (Abs) produced by immunoglobulin (IG) genes are the most diverse proteins expressed in humans. While part of this diversity is generated by recombination during B-cell development and mutations during affinity maturation, the germ-line IG loci are also diverse across human populations and ethnicities. Recently, proof-of-concept studies have demonstrated genotype–phenotype correlations between specific IG germ-line variants and the quality of Ab responses during vaccination and disease. However, the functional consequences of IG genetic variation in Ab function and immunological outcomes remain underexplored. In this opinion article, we outline interconnections between IG genomic diversity and Ab-expressed repertoires and structure. We further propose a strategy for integrating IG genotyping with functional Ab profiling data as a means to better predict and optimize humoral responses in genetically diverse human populations, with immediate implications for personalized medicine.

Genetic variation in human populations affects how individuals are able to mount functional antibody responses.

Different alleles can encode convergent binding motifs that result in successful Ab responses against specific infections and vaccinations.

Given the complexity of the IG loci and the diversity of the antibody repertoire, links between IG polymorphism and antibody repertoire variability have not been thoroughly explored.

We present a strategy to mine genotype–repertoire–disease associations.

Hepatitis B virus-associated diffuse large B-cell lymphoma: unique clinical features, poor outcome, and hepatitis B surface antigen-driven origin

While the epidemiologic association between hepatitis B virus (HBV) infection and diffuse large B-cell lymphoma (DLBCL) is established, little is known more than this epidemiologic evidence. We studied a cohort of 587 patients with DLBCL for HBV infection status, clinicopathologic features, and the immunoglobulin variable region in HBV surface antigen (HBsAg)-positive patients. Eighty-one (81/587, 13.8%) patients were HBsAg-positive. Compared with HBsAg-negative DLBCL, HBsAg-positive DLBCL displayed a younger median onset age (45 vs. 55 years), more frequent involvement of spleen or retroperitoneal lymph node (40.7% vs. 16.0% and 61.7% vs. 31.0% respectively, both p < 0.001), more advanced disease (stage III/IV: 76.5% vs 59.5%, p = 0.003), and significantly worse outcome (2-year overall survival: 47% versus 70%, p < 0.001). In HBsAg-positive DLBCL patients, almost all (45/47, 96%) amino acid sequences of heavy and light chain complementarity determining region 3 exhibited a high homology to antibodies specific for HBsAg, and the majority (45/50, 90%) of IgHV and IgLV genes were mutated. We conclude that 13.8% of DLBCL cases are HBV-associated in HBV-endemic China and show unique clinical features and poor outcomes. Furthermore, our study strongly suggests that HBV-associated DLBCL might arise from HBV antigen-selected B cells.

Molecular and genomic aberrations in Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

The etiology and pathogenesis of ocular adnexal extranodal marginal zone lymphoma (OAEMZL) are still unknown and the association with Chlamydophila psittaci (C. psittaci) has been shown in only some geographic regions. Herein, we comprehensively examined the frequency of chromosomal translocations as well as CARD11, MYD88 (L265P), and A20 mutations/deletions in 45 C. psittaci negative OAEMZLs. t(14;18)(q32;q21) IGH-MALT1 and t(11;18)(q21;q21) API2-MALT1 were not detected in any of the analyzed tumors while three tumors harbored IGH translocations to an unidentified partner. CARD11 mutations were not found in all analyzed tumors, while the MYD88 L265P mutation was detected in three (6.7%) tumors. A20 mutations and deletions were each detected in seven (15.6%) and six (13.3%) tumors, respectively. Therefore, the observed genetic aberrations could account for the activation of the nuclear factor (NF)-kB signaling pathway in only a minority of the cases. Further studies are needed to identify the molecular mechanisms underlying the pathogenesis of OAEMZL.