The Src family tyrosine kinase Fyn regulates natural killer T cell development

T lymphocytes express two Src tyrosine kinases, Lck and Fyn. While thymocyte and T cell subsets are largely normal in fyn(-/-) mice, animals lacking Lck have impaired T cell development. Here, it is shown that Fyn is required for the rapid burst of interleukin (IL)-4 and IL-13 synthesis, which occurs promptly after T cell receptor activation. The lack of cytokine induction in fyn mutant mice is due to a block in natural killer (NK) T cell development. Studies using bone marrow chimeras indicate that the defect behaves in a cell-autonomous manner, and the lack of NK T cells is probably not caused by inappropriate microenvironmental cues. Both NK T cells and conventional T cells express similar levels of Lck, implying that Fyn and Lck have distinct roles in regulating NK T cell ontogeny. The fyn mutation defines the first signaling molecule that is selectively required for NK T cell, but not for T lymphocyte or NK cell development.

Molecular approaches to the diagnosis and evaluation of lymphoid malignancies

The processes of somatic immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangement that occur in lymphoid precursors provide insights into the pathogenesis and molecular analysis of lymphoid malignancies, in addition to the more universal molecular oncogenic mechanisms. Detection of lymphoid clonality can help distinguish polyclonal reactive disorders from clonal, predominantly, but not exclusively, malignant proliferations. Ig/TCR V-(D)-J polymerase chain reaction (PCR) amplification has largely replaced Southern blotting, and the techniques of PCR product analysis are evolving rapidly. V-(D)-J errors are often involved in genetic abnormalities leading to lymphoid malignancies, with consequent deregulated expression of the associated proto-oncogenes. Genetic abnormalities producing fusion transcripts and chimeric proteins are also frequent, particularly in acute lymphoblastic leukemia (ALL). A variety of molecular techniques, including reverse-transcriptase (RT)-PCR, Southern blotting, and fluorescence in situ hybridization (FISH) are finding an increasingly established place in the diagnosis, prognostic evaluation, therapeutic stratification, and follow-up of lymphoblastic leukemias, and it is likely that the same methods will be applied to non-Hodgkin's lymphoma (NHL) and to chronic leukemias.

Marginal-zone B cells in the human lymph node and spleen show somatic hypermutations and display clonal expansion

Splenic marginal-zone B cells, marginal-zone B cells of Peyer's patches in the gut, and nodal marginal-zone B cells (also identified as monocytoid B cells) share a similar morphology and immunophenotype. These cells likely represent a distinct subset of B cells in humans and rodents, but their precise ontogenetic relationship as well as their origin from B cells of the germinal center is still debated. To study this, we performed a mutation analysis of the rearranged immunoglobulin variable genes (VH) of microdissected single nodal and splenic marginal-zone cells. In addition, we investigated the presence of proliferating cells and B-cell clones in the human splenic and nodal marginal zone as well as adjacent germinal centers. This was performed by immunohistochemical staining for the Ki-67 antigen and denaturing gradient gel analysis of amplified immunoglobulin heavy chain genes' complementarity determining region 3 of microdissected cell clusters. A variable subset of nodal and splenic marginal-zone B cells showed somatic mutations in their rearranged VH genes, indicating that both virgin and memory B cells are present in the nodal and splenic marginal zone. Nodal and splenic marginal-zone B cells preferentially rearranged VH3 family genes such as DP47, DP49, DP54, and DP58. A preferential rearrangement of the same VH genes has been shown by others in the peripheral CD5(-) IgM+ B cells. These data suggest that the splenic and nodal marginal-zone B cells are closely related B-cell subsets. We also showed that marginal-zone B cells may cycle and that clones of B cells are frequently detected in the nodal as well as the splenic marginal zone. These clones are not related to those present in adjacent germinal centers. These data favor the hypothesis that clonal expansion occurs in the marginal zone. Whether the somatic hypermutation mechanism is activated during the clonal expansion in the marginal zone and which type of immune response triggers the clonal expansion need to be elucidated.

Equine SCID: mechanistic analysis and comparison with murine SCID

V(D)J rearrangement is the molecular mechanism by which an almost limitless number of unique immune receptors is generated. V(D)J rearrangement involves two DNA breaks and religations resulting in two DNA joints; coding and signal joints. If V(D)J recombination is impaired (as in murine SCID (C.B-17 mouse] or RAG [Recombinase Activating Genes) deficient mice), B lymphocyte and T lymphocyte development is blocked and severe immunodeficiency results. The first animal model of SCID was reported in Arabian foals in 1973. Recently we demonstrated that the mechanistic defect in SCID foals is V(D)J recombination. However, the impairment of V(D)J recombination in SCID foals is phenotypically distinct from SCID mice in that both signal and coding joint ligation are impaired. Furthermore, though equine SCID and murine SCID have definite phenotypic differences, both defects are likely to be the result of defective expression of the catalytic subunit of the DNA-dependent protein kinase.

Inherent properties of somatic hypermutation as revealed by human non-productive VH6 immunoglobulin rearrangements

To study inherent properties of somatic hypermutation of human immunoglobulin genes in the absence of antigen selection, mutations of human non-productive VH6 rearrangements enriched by subtractive hybridization were characterized. Ten unique clones arising from nine non-productive rearrangements were isolated. The frequency of mutation was 3.0%. Analysis of these mutations showed intrinsic bias for transitions and cytosine (C) to guanine (G) and G to C transversions. Bias for the strand of DNA targeted by mutation was not evident. Replacement mutations in the complementarity-determining region (CDR) occurred more frequently than expected based on the primary DNA sequence. This targeting of replacement mutations to the CDR may explain the conservation of the VH6 sequence in primates.

Reappraisal of the relationship between immunoglobulin heavy chain gene rearrangement and Epstein-Barr virus infection in Reed-Sternberg cells of Hodgkin's disease

We investigated 44 cases of Hodgkin's disease for Epstein-Barr virus genome with EBER-1 in situ hybridization. Twenty of 44 (45.5%) were positive for EBV. Simultaneously, immunoglobulin gene rearrangements were assessed in 32 of these 44 cases with PCR on DNA extracted from Reed-Sternberg cell (RS-cell) -rich areas microdissected from paraffin sections. Clonally rearranged immunoglobulin (IgH) gene was observed in 15 cases (46.9%). EBV-negative cases showed more frequent IgH rearrangement than EBV-positive cases (10 and 5 cases, respectively). In 9 cases, the RS cells were CD20-positive immunohistochemically and these were all EBV negative and the IgH gene was rearranged in all except one. These findings may suggest that EBV infection has occurred before the immunoglobulin gene rearrangement or that EBV infection has influenced the rearrangement of the immunoglobulin gene. The results may also hint towards the obscure B-cell nature of the RS cells.

Hypermutation, diversity and dissemination of human intestinal lamina propria plasma cells

In this work we have microdissected lamina propria plasma cells and used polymerase chain reaction and sequencing to investigate immunoglobulin (Ig) gene rearrangements and mutations in human intestine. In addition, specific primers were designed for individual Ig gene rearrangements to analyze the distribution of related B cell and plasma cell clones at different sites along the bowel. Confirming our earlier work, intestinal IgVH genes were highly mutated in plasma cells from older individuals (> 30 years). IgVH genes were significantly less mutated in samples taken from patients aged 11-30 years, and there were fewer mutations again in samples from young children (< 11 years). In age-matched specimens the number of mutations was equivalent in the duodenum and colon. Using complementarity-determining region 3 primers to amplify specific Ig gene rearrangements, evidence was also found for the existence of related lamina propria plasma cells along the small bowel and colon, although these were quite scarce. In addition, analysis of the numbers of related clones in a random sampling from discrete areas of lamina propria indicates that the local population is diverse. These results suggest that the highly mutated IgVH genes in adult intestinal plasma cells are a consequence of chronic antigen exposure with age. Duodenal plasma cells are as highly mutated as colonic plasma cells, despite the fact that the upper bowel has no indigenous microbial flora (the stimulus for intestinal plasma cells). They also show that the plasma cell population is diverse and can be widely disseminated along the bowel.

Abbreviated junctional sequences impoverish antibody diversity in urodele amphibians

Of the six complementarity-determining regions (CDR) forming the structure of the Ab combining site, CDR3 of heavy chain is the most variable in length and sequence. Diversity of this loop is determined by the number of gene segments involved, extent of addition to or deletion from the joining genes, and imprecision of the site of recombination. In neonatal mice and Xenopus tadpoles, the last two factors occur less frequently than in adults, which in tadpoles result in low affinity Ab responses that do not mature. In contrast, adult urodele amphibians make larval-like responses and are notorious for lifelong poor immunocompetence. The mechanism for this is not known, and in this study we cloned germline VH genes from the axolotl and obtained rearrangements to these VH gene segments by reverse-transcriptase PCR. These sequences were analyzed for heavy chain junctional diversity and found to be even less variable than that in newborn mouse or Xenopus tadpoles, although for different reasons. Only 29% of the CDR3 loop in the axolotl consisted of somatically generated sequences, compared with 44% in tadpole, 39% in newborn mice, and 57% in both adult mice and Xenopus. This distinguishing feature of axolotl CDR3 results not only from shorter junctional sequences, but also unusually extensive integration of germline JH sequence. As the CDR3 loop is the most important portion of the Ig sequence for determining Ab combining site diversity, our data provide the molecular basis for a contributing factor in the deficient urodele amphibian Ab responses.

Aberrant V(H) gene utilization in patients with established insulin dependent diabetes mellitus

We have compared the B-lymphocyte repertoire in seven IDDM patients with 12 healthy controls by examining the variable heavy (V(H)) gene expression. The V(H) gene representation in the pool of pokeweed mitogen (PWM) stimulated, immunocompetent B cells and in the pool of naturally activated plasma cells (actual repertoire) was analysed by RNA-RNA in situ hybridization. Differences between IDDM patients and normal controls in the relative expression of several V(H) gene families were observed. In IDDM patients, the V(H)3 was significantly underrepresented in the PWM stimulated repertoire. In the actual B cell repertoire the V(H)5 clones were underrepresented among diabetic patients. Moreover, the altered distribution of V(H) gene usage between the PWM stimulated repertoire and the actual repertoire observed in normal controls was found to be less pronounced in the IDDM patients. This observation suggests a defect in the V-gene directed cellular selection occurring between resting, immunocompetent B cells and naturally activated plasma cells. The possible implication of the observed aberrations in the B cell selection process for the pathogenesis of autoimmunity is discussed.

Specificity in V(D)J recombination: new lessons from biochemistry and genetics

Recent in vitro work on V(D)J recombination has helped to clarify its mechanism. The first stage of the reaction, which can be reproduced with the purified RAG1 and RAG2 proteins, is a site-specific cleavage that generates the same broken DNA species found in vivo. The cleavage reaction is closely related to known types of transpositional recombination, such as that of HIV integrase. All the site specificity of V(D)J recombination, including the 12/23 rule, is determined by the RAG proteins. The later steps largely overlap with the repair of radiation-induced DNA double-strand breaks, as indicated by the identity of several newly characterized factors involved in repair. These developments open the way for a thorough biochemical study of V(D)J recombination.

Mechanism of antigen-driven somatic hypermutation of rearranged immunoglobulin V(D)J genes in the mouse

Available data relevant to the mechanism of somatic hypermutation have been critically evaluated in the context of alternative models: (i) error-generating reverse transcription (RT) followed by homologous recombination; and (ii) error-prone DNA replication/repair. A set of basic principles concerning somatic hypermutation has also been formulated and a revised and expanded "RT-Mutatorsome" concept (analogous to telomerase) is presented which is consistent with these principles and all data on the distribution of somatic mutations in normal and Ig transgenic mice carrying particular V(D)J and flanking region constructs. It is predicted that in the mouse VH and Vk loci. the J-C intronic Enhancer-Nuclear Matrix Attachment Region (Ei/MAR) contains a unique sequence motif or secondary structure which ensures that only V(D)J sequences mutate whilst other regions of the genome are not mutated.

Constitutive expression of terminal deoxynucleotidyl transferase in transgenic mice is sufficient for N region diversity to occur at any Ig locus throughout B cell differentiation

N region diversity in Ag receptors is a developmentally regulated process in B and T cells that correlates with the differential expression of terminal deoxynucleotidyl transferase (TdT). Absent in fetal and newborn mice, TdT expression is restricted to early T and pro-B cells in adults. To extend the TdT expression pattern throughout B cell ontogenesis, we generated transgenic mice carrying a TdT cDNA under the regulatory elements of the N-myc gene and the IgH enhancer. High expression was observed in secondary lymphoid organs consistent with TdT activity beyond the pre-B cell stage. This suggests that TdT transgene expression is not down-regulated as is the endogenous gene. Unlike normal mice, extensive N region diversity was found in rearranged lambda light chain genes of adult transgenic animals. Therefore, expression of TdT appears sufficient for N region diversity to occur at any Ig locus. More importantly, expression of the transgene takes place during fetal development. As a consequence, the potential fetal B cell repertoire is modified as both rearranged heavy and light chain genes now show N region additions. Constitutive expression of TdT throughout B cell differentiation does not therefore appear deleterious and suggests that TdT is recruited only to participate in the V(D)J recombination process.

Restricted immunoglobulin VH region repertoire in chronic lymphocytic leukemia patients with autoimmune hemolytic anemia

Between 10% and 25% of chronic lymphocytic leukemia (CLL) patients have episodes of autoimmune hemolytic anemia (AIHA) during the course of their disease. The anti-erythrocyte autoantibodies in most cases are polyclonal and express a different heavy chain isotype than the malignant clone, indicating that they are secreted by normal autoreactive B lymphocytes. To further investigate the pathogenesis of the AIHA in CLL, we analyzed the lg heavy (H) chain variable region genes expressed by leukemic cells from CLL patients with and without AIHA. Two VH genes were preferentially expressed by the leukemic cells in the CLL cases with AIHA and were present in 9 of the 12 investigated cases. The 51p1/DP-10 gene was expressed in 5 of these cases and was absent in the control group of 12 consecutive CLL cases without AIHA, whereas the DP-50 gene was present in 4 CLL-AIHA cases and only once in the control CLL group. A strikingly similar H-chain CDR3 region that contained a single reading frame of the DXP4 DH gene segment, and N-encoded proline at the DH/JH boundary, and a tyrosine-rich region encoded by the JH6 gene segment was observed in four CLL-AIHA cases. The preferential expression of two VH gene segments and a particular CDR3 region by the leukemic cells of patients with AIHA suggests that the antibodies produced by the CLL cells are directly involved in the pathogenesis of the hemolytic anemia.

Potential targets for autosomal SCID mutations

Significant advances have been recently made in the molecular characterization of genes that encode proteins with activities that are directly, or indirectly, involved in the assembly of antigen receptor variable region genes. Such genes are candidate targets for human autosomal mutations that lead to severe combined immune deficiencies characterized by a lack of both T and B cells.

Review of investigative diagnostic techniques for cutaneous lymphoma

This article reviews the contribution of modern investigative techniques to the diagnosis of cutaneous lymphoproliferative diseases. Special attention is given to the significance of immunoglobulin and T-cell receptor rearrangements; as detected by Southern blotting and/or the polymerase chain reaction. Additional topics discussed include immunohistochemistry, cytogenetics, onco- and tumour suppressor genes and in-situ hybridization. It is recommended that the results of these techniques are interpreted in the form of a multifaceted diagnostic profile.

The mechanism of V(D)J recombination: site-specificity, reaction fidelity and immunologic diversity

Site-specific recombination reactions in higher eukaryotes are uncommon, perhaps because of the potential genomic instability that they may create. We focus this review on the issues of site-specificity, reaction fidelity and immunologic diversity in the V(D)J recombination reaction.

Cytokeratin in anaplastic large cell lymphoma

A B-cell anaplastic large cell lymphoma, confirmed by immunohistochemistry and Southern blot immunoglobulin gene rearrangement analysis, contained neoplastic cells that were immunoreactive for cytokeratin using antibodies CAM 5.2, M20, MAK 6, and KS-B17.2. Bands corresponding to cytokeratin 18 and cytokeratins 18 and 8 were seen on Western blot immunoanalysis using antibodies KS-B17.2 and CAM 5.2. The lymph node also contained cytokeratin-positive extrafollicular fibroblastic reticulum cells. Although it is possible that the presence of cytokeratin in the cells of anaplastic large cell lymphoma represented phagocytosed filaments from the reticulum cells, it is more likely that the cytokeratins were synthesized by the malignant cells. The finding of cytokeratin in anaplastic large cell lymphoma, although infrequent, adds to the confusion in the diagnosis of this pleomorphic neoplasm.

Detection of clonal platelet antibodies in immunologically-mediated thrombocytopenias: association with circulating clonal/oligoclonal B cells

Aware that T and B cells in autoimmune thrombocytopenia are abnormal, including the existence of clonal B cell populations, we sought to characterize this clonal phenomenon in various immunological thrombocytopenias using platelet antibody light chain analysis, flow cytometry, Southern blot analysis, and PCR. Using a monoclonal antibody-antigen capture ELISA, we analysed sera from 21 of 26 patients with autoimmune, alloimmune, or drug-induced immunological thrombocytopenia for the light chain phenotypes of their platelet antibodies. Alloantibodies and drug-dependent antibodies from four and 14 patients, respectively, were found that expressed a predominant type of light chain, suggesting that these platelet-reactive antibodies were monoclonal or oligoclonal in nature. 14 of the 26 patients were available for light chain B cell phenotyping studies. Of these 14 patients, thrombocytopenia was due to autoimmunity in two, drug-induced immunity in four, and alloimmunity in eight. We detected clonal populations of B cells in all 14 patients by flow cytometry. Although six of these latter patients possessed platelet antibodies with clonal characteristics, light chain phenotypes of antibodies in five patients were opposite to those of their B cells. Eight of these patients were further examined for immunoglobulin gene rearrangement using Southern and/or polymerase chain reaction analysis. In all eight patients we detected clonal or oligoclonal B cell populations. Only two of these patients had malignancies (chronic lymphocytic leukaemia) that would be expected to have detectable clonal B cells, and thus the mechanism for clonal expansion in the other six patients did not appear to be related to an obvious neoplastic process. Prior to these studies, detection of clonal B cells in thrombocytopenic patients without known malignancies was limited to individuals with autoimmune thrombocytopenia, prompting the speculation that this particular autoimmune disorder arises from B cell dysregulation, rather than from expansion of specific autoantibody producing B cell clones. In contrast, the current studies provide evidence that clonal B cells are common to patients with any form of immunologically-mediated thrombocytopenia. Moreover, the majority of the platelet antibodies (86%) present in these disorders exhibited monoclonal characteristics in that there was an apparent restriction in light chain usage.

Analysis of rearranged immunoglobulin genes indicating a process of clonal evolution in chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is known to be a stable monoclonal neoplasm. In contrast to early studies demonstrating no more than two hybridizing immunoglobulin heavy chain bands corresponding to the two expected alleles, we have demonstrated an unexpected multiband pattern when the HindIII-digested DNA samples from 38 CLL patients were analysed by Southern blot hybridization using JH and C mu gene probes. In order to characterize the genetic basis for the multiband pattern, we molecularly cloned the immunoglobulin heavy chain genes of one of the patients whose leukaemic DNA sample demonstrated three hybridizing JH bands and a loss of the germline band. The cloned rearranged immunoglobulin genes could be divided, based on the restriction mapping and the hybridization with the various probes, into two basic patterns representing two alleles. In one of the cloned rearranged immunoglobulin genes a secondary rearrangement occurred that resulted in the addition of 300 base-pair long sequence into the switch region, and the creation of a HindIII restriction site. The results of the study suggest that clonal evolution occurs in some CLL, and that many of these neoplasms are indeed oligoclonal due to the accumulation of secondary genetic changes.

Rapid method for detecting monoclonality in B cell lymphoma in lymph node aspirates using the polymerase chain reaction

AIMS

To use the polymerase chain reaction to detect monoclonality at the immunoglobulin heavy chain gene locus in cells derived from lymph node aspirates.

METHODS

A nested two-stage polymerase chain reaction (PCR) for the VDJ region of the immunoglobulin heavy chain gene was used to detect monoclonality. The total number of cells available for diagnosis by PCR in lymph node aspirates was between 10(4) and 10(5).

RESULTS

A monoclonal band was detected in 21 of 25 malignant B-lymphomas. The other four specimens gave polyclonal bands. Specimens from reactive lymph nodes produced polyclonal bands in 14 cases, no product in two cases, and one specimen gave two monoclonal bands. Polyclonal bands were obtained for three Hodgkin's lymphoma samples and five metastatic carcinomas. Four metastatic carcinoma samples gave no amplification.

CONCLUSIONS

Detection of monoclonality in a cell population is strongly suggestive of malignant disease. The simple PCR method presented here should complement conventional cytological and immunological methods for diagnosis of malignancy by lymph node aspirates.

Epstein-Barr virus and HIV play no direct role in persistent generalized lymphadenopathy syndrome

Persistent generalized lymphadenopathy (PGL) and polyclonal B cell activation are features of infection with HIV. Epstein-Barr virus (EBV) and HIV are known to activate B cells in vitro, but whether they are important B cell activators in patients infected with HIV is less clear. In this study, lymph node tissue was obtained from 10 patients with PGL and assessed for evidence of EBV and HIV gene sequences. DNA was extracted and specific viral gene sequences identified using the polymerase chain reaction (PCR). EBV sequences were difficult to detect in the PGL tissue, with a signal intensity similar to that of other benign and malignant lymphoid conditions not associated with EBV. HIV sequences were also rare in the PGL tissue, consistent with HIV infection of the small number of peripheral blood cells and nodal T cells likely to be present in such a sample. These findings suggest that the polyclonal B cell activation typical of HIV is not driven by direct EBV or HIV infection of B cells.

A specific T-cell receptor genotype preference in the immune response to a synthetic Plasmodium falciparum malaria vaccine

In recent studies with 63 and 122 volunteers vaccinated with the SPf 66 synthetic malaria vaccine, specific antibody patterns were classified as high or low responders. Using the Polymerase Chain Reaction (PCR), a specific and selective preference was shown for the V beta arrangement of the T-cell receptor in the high responder group involving the V beta-8 gene. The low responder group showed the rearrangement of a different set of genes, and a particular association with V beta-10.

Prognostic value of lymphocyte surface markers in acute myeloid leukemia

We studied the expression of cell surface antigens associated with myeloid and lymphoid leukemias on bone marrow-derived blast cells from 339 patients with newly diagnosed de novo acute myeloid leukemia (AML) enrolled on Cancer and Leukemia Group B (CALGB) chemotherapy protocols. Surprisingly, of 211 cases studied for the expression of CD2 (T-cell marker, sheep erythrocyte binding receptor for T lymphocytes) 45 were positive (21%). In addition, of 298 patients studied for CD19 (B-lymphocyte marker), 41 were positive (14%). Overall, of 170 patients studied for both CD2 and CD19, 56 (33%) were positive. Interestingly, central review of the French-American-British (FAB) morphology of the CD2- and CD19-positive cases showed that FAB M3 was twice as frequent, and M4E eight times as frequent compared with the CD2- and CD19-negative cases. Of 22 lymphocyte antigen-positive cases in which cells were available for studies of Ig or T-cell antigen receptor (TCR) gene rearrangement, 20 were germline, one had a rearranged Ig heavy chain gene, and one had rearranged TCR beta and Ig heavy chain genes. The presence of messenger RNA for CD2 was demonstrated in four CD2 surface antigen-positive cases, thus validating the cell surface data. Lymphocyte antigen-positive cases had karyotypes commonly seen in AML; 71% of cases with an abnormal clone had t(8;21)(q22;q22), inversion 16(p13q22), t(15;17)(q22;q12), or t(9;11)(p22;q23). The patients with lymphocyte markers had a significantly higher incidence of these karyotypic abnormalities compared with patients with lymphocyte antigen-negative AML (34% v 15%, P less than .02). When the outcome to therapy of the lymphocyte antigen-positive cases was compared with that for the CD2, CD19-negative cases, we found that the CD2, CD19-positive cases actually had higher complete remission rates (75% v 59%, P = .04), and significantly longer time to failure (P = .02; 32.4% +/- 6.0% v 18.0% +/- 4.1% at 2 years) and overall survival (P = .02; 43.5% +/- 6.3% v 26.0% +/- 4.5% at 2 years). CD2 antigen-positive cases also had a significantly superior survival (P = .02; 43.8% +/- 7.9% v 29.8% +/- 3.8% at 2 years). There were no significant differences (P less than or equal to .05) between the two groups in age, leukocyte count at diagnosis, incidence of extramedullary disease, or FAB classification.(ABSTRACT TRUNCATED AT 400 WORDS)