Leukemia Associated Clonal Expansion of TCR Vβ Subfamily T Cells

The analysis of the T cell receptor (TCR) Vβ repertoire is one of the most sensitive methods to identify the clonal expansion T cells which respond to tumor associated antigens. Recently, studies have focused on clonally expanded T cells from patients or normal donors induced by leukemia associated antigens in vivo or in vitro. Understanding such clonality and restricted usage of TCR Vβ repertoire of leukemia-associated expanded T cells may be useful for the design of new immunotherapeutic strategy for leukemia.     

VH gene analysis of Burkitt's lymphoma in children from north-western Iran

Cases of Burkitt's lymphoma (BL) from north-western Iran were investigated for the usage and somatic mutational pattern of their immunoglobulin variable region genes. Potentially functional V_H genes were amplified from 6/12 of the tumour masses and all of these were derived from the V_H3 family, with 4/6 being derived from the most commonly used V_H3 family member, V_3-23. All of the tumour sequences were mutated from their germline counterparts, to varying degrees, with a mean level of 5.8%, indicating that the cell of origin had encountered the germinal centre. Intraclonal sequence heterogeneity was also evident in 4/6 of the lymphomas, showing that the tumour cells had undergone further somatic mutation following neoplastic transformation. Analysis of the five potentially functional mutated V_H sequences showed a significant clustering of replacement mutations in the complementarity-determining region 2, consistent with a role for antigen in selection of tumour cell sequences. The pattern of extensive somatic mutation, and intraclonal variation, in these mainly EBV+ve tumours, was similar to that previously reported in V_H sequences of EBV+ve endemic BL (eBL) and EBV−ve sporadic BL (sBL), with the mean level of somatic mutation lying between those reported for eBL (7.7%) and sBL (4.0%). However, V_H gene bias and the distribution of mutations in the Iranian cases showed features which differed from those reported for endemic or sporadic BL.     

Hepatitis C Virus Epitope Immunodominance and B Cell Repertoire Diversity

Despite the advent of effective, curative treatments for hepatitis C virus (HCV), a preventative vaccine remains essential for the global elimination of HCV. It is now clear that the induction of broadly neutralising antibodies (bNAbs) is essential for the rational design of such a vaccine. This review details the current understanding of epitopes on the HCV envelope, characterising the potency, breadth and immunodominance of antibodies induced against these epitopes, as well as describing the interactions between B-cell receptors and HCV infection, with a particular focus on bNAb heavy and light chain variable gene usage. Additionally, we consider the importance of a public repertoire for antibodies against HCV, compiling current knowledge and suggesting that further research in this area may be critical to the rational design of an effective HCV vaccine.     

The Complete Nucleotide Sequence of the Human Immunoglobulin Heavy Chain Variable Region Locus

The complete nucleotide sequence of the 957-kb DNA of the human immunoglobulin heavy chain variable (V_H) region locus was determined and 43 novel V_H segments were identified. The region contains 123 V_H segments classifiable into seven different families, of which 79 are pseudogenes. Of the 44 V_H segments with an open reading frame, 39 are expressed as heavy chain proteins and 1 as mRNA, while the remaining 4 are not found in immunoglobulin cDNAs. Combinatorial diversity of V_H region was calculated to be ∼6,000. Conservation of the promoter and recombination signal sequences was observed to be higher in functional V_H segments than in pseudogenes. Phylogenetic analysis of 114 V_H segments clearly showed clustering of the V_H segments of each family. However, an independent branch in the tree contained a single V_H, V4-44.1P, sharing similar levels of homology to human V_H families and to those of other vertebrates. Comparison between different copies of homologous units that appear repeatedly across the locus clearly demonstrates that dynamic DNA reorganization of the locus took place at least eight times between 133 and 10 million years ago. One nonimmunoglobulin gene of unknown function was identified in the intergenic region.     

Somatic diversification of the B cell repertoire requires two cell subsets

Evolution found itself in a Catch‐22 situation when selecting for the somatically derived paratopic repertoire of the humoral immune system. The B cell BCR repertoire can only be somatically diversified from a substrate of paratopes that is encoded in the germline. In order for the cells expressing that substrate to also be a target of germline selection, their BCR s must, independently, be of selective value by being expressed in a functionally important way in each individual. A somatically derived repertoire scrambles this substrate so that its specificities are lost, making it unselectable in the germline. Consequently, evolution faced an incompatibility. Here, we explore what it takes to resolve it.     

Biased JH usage in plasma cell immunoglobulin gene sequences from colonic mucosa in ulcerative colitis but not in Crohn's disease

BACKGROUND: Ulcerative colitis is an inflammatory disease of the colonic and rectal mucosa. Autoantibodies have been observed in ulcerative colitis which may have a role in the pathogenesis of the disease. Evidence also suggests that there is an hereditary predisposition towards the disease, although no individual genes have been identified. AIMS: This is a pilot study of immunoglobulin heavy chain genes (IgH) in ulcerative colitis to determine whether they have any particular genetic characteristics which may lead to a better understanding of the disease aetiology. SUBJECTS: Colonic or rectal tissue was obtained from five children with ulcerative colitis. Tissue was also obtained from five children with Crohn's disease and five children who did not have inflammatory bowel disease as controls. METHODS: B cells and IgD+ B cells were identified by immunohistochemistry on frozen sections. Areas of lamina propria containing plasma cells, and areas of IgD+ B cells were microdissected. The immunoglobulin genes were PCR amplified, cloned, and sequenced. Sequences were analysed for content of somatic mutations and composition of heavy chain. RESULTS: An increase in the use of JH6 and DXP'1, and a decrease in the use of JH4, gene segments in immunoglobulin genes from lamina propria plasma cells, and from virgin IgD+ B cells, was found in patients with ulcerative colitis. These biases were not present in the control groups. CONCLUSIONS: There is a fundamental difference in the immunoglobulin genes from patients with ulcerative colitis. Whether this is caused by a difference in content of immunoglobulin gene segments in the germline or a difference in the recombination mechanism is not known.     

The effect of haptens on protein‐carrier immunogenicity

The immune response against hapten is T‐cell‐dependent, and so requires the uptake, processing and presentation of peptides on MHC class II molecules by antigen‐presenting cells to the specific T cell. Some haptens, following conjugation to the available free amines on the surface of the carrier protein, can reduce its immunogenicity. The purpose of this study was to explore the mechanism by which this occurs. Four proteins were tested as carriers and six molecules were used as haptens. The immune response to the carrier proteins was reduced > 100‐fold by some of the haptens (termed carrier immunogenicity reducing haptens – CIRH), whereas other haptens did not influence the protein immunogenicity (carrier immunogenicity non‐reducing haptens – nCIRH). Conjugation of the protein to a CIRH affected protein degradation by lysosomal cathepsins, leading to the generation of peptides that differ in length and sequence from those derived from the same native protein or that protein modified with nCIRH. Injection of CIRH‐conjugated protein into mice induced an increase in the population of regulatory T cells. The results of this study provide a putative mechanism of action for the reduction of immune response to haptenated proteins.