Precursor B-cell lymphoblastic leukemia with surface immunoglobulin light chain expression in 2 chinese patients

BACKGROUND

Precursor B-cell acute lymphocytic leukemia (ALL) with surface immunoglobulin light chain expression is a rare disease entity. The differential diagnosis is difficult but critical for disease management.

AIMS

We report 2 cases (1 adult and 1 infant) of precursor B-cell ALL who presented at diagnosis with surface immunoglobulin light chain expression revealed by flow cytometric immunophenotyping and discuss its clinical significance.

CASE REPORT

The 2 patients presented with nonspecific symptoms such as fever, pallor, fatigue or lymphadenopathy. Flow cytometric immunophenotyping showed that both patients expressed CD34/CD19/CD10/CD22/CD9/HLA-DR/CD38/CD123/CD13 (partial) and had unexpected single λ light chain expression. Cytogenetic analysis revealed t(9;22)(q34;q11) in the adult patient and normal karyotype in the infant. Both cases were diagnosed and managed as precursor B-ALL, and the patients showed good response to treatment regimens.

CONCLUSION

We describe 2 cases of precursor B-ALL with unexpected surface light chain expression. The exceedingly rare immunophenotypes have diagnostic implication for immunophenotyping of this malignancy. Treatment regimens for precursor B-cell ALL are suitable for such cases.

[Improved prognosis in light chain nephropathy due to multiple myeloma]

A 64 year-old woman with acute renal failure and cast nephropathy due to excessive production of lambda free light chains received chemotherapy (using bortezomib and dexamethason) and haemodialysis with a high cut off-filter. The concentration of free light chains was markedly reduced after a fortnight. Nine months after admission, the patient's kidney function had improved and dialysis was stopped. Three months later, she got an autologous stem cell transplantation. One year later, estimated glomerular filtration rate was 25 ml/min, and the production of free light chains was under control.

Receptor editing in self-reactive bone marrow B cells. The Journal of Experimental Medicine. 1993. 177: 1009-1020

A central paradigm of immunology is clonal selection: lymphocytes displaying clonally distributed antigen receptors are generated and subsequently selected by antigen for growth or elimination. Here we show that in mice transgenic for anti-H-2Kk,b antibody genes, in which a homogeneous clone of developing B cells can be analyzed for the outcome of autoantigen encounter, surface immunoglobulin M+/idiotype+ immature B cells binding to self-antigens in the bone marrow are induced to alter the specificity of their antigen receptors. Transgenic bone marrow B cells encountering membrane-bound Kb or Kk proteins modify their receptors by expressing the V(D)J recombinase activator genes and assembling endogenously encoded immunoglobulin light chain variable genes. This (auto)antigen-directed change in the specificity of newly generated lymphocytes is termed receptor editing.

Analysis of expressed and non-expressed IGK locus rearrangements in chronic lymphocytic leukemia

Immunoglobulin kappa (IGK) locus rearrangements were analyzed in parallel on cDNA/genomic DNA in 188 kappa- and 103 lambda-chronic lymphocytic leukemia (CLL) cases. IGKV-KDE and IGKJ-C-intron-KDE rearrangements were also analyzed on genomic DNA. In kappa-CLL, only 3 of 188 cases carried double in-frame IGKV-J transcripts: in such cases, the possibility that leukemic cells expressed more than one kappa chain cannot be excluded. Twenty-eight kappa-CLL cases also carried nonexpressed (nontranscribed and/or out-of-frame) IGKV-J rearrangements. Taking IGKV-J, IGKV-KDE, and IGKJ-C-intron-KDE rearrangements together, 38% of kappa-CLL cases carried biallelic IGK locus rearrangements. In lambda-CLL, 69 IGKV-J rearrangements were detected in 64 of 103 cases (62%); 24 rearrangements (38.2%) were in-frame. Four cases carried in-frame IGKV-J transcripts but retained monotypic light-chain expression, suggesting posttranscriptional regulation of allelic exclusion. In all, taking IGKV-J, IGKV-KDE, and IGKJ-C-intron-KDE rearrangements together, 97% of lambda-CLL cases had at least 1 rearranged IGK allele, in keeping with normal cells. IG repertoire comparisons in kappa- versus lambda-CLL revealed that CLL precursor cells tried many rearrangements on the same IGK allele before they became lambda producers. Thirteen of 28 and 26 of 69 non-expressed sequences in, respectively, kappa- or lambda-CLL had < 100% homology to germline. This finding might be considered as evidence for secondary rearrangements occurring after the onset of somatic hypermutation, at least in some cases. The inactivation of potentially functional IGKV-J joints by secondary rearrangements indicates active receptor editing in CLL and provides further evidence for the role of antigen in CLL immunopathogenesis.

Four primordial immunoglobulin light chain isotypes, including lambda and kappa, identified in the most primitive living jawed vertebrates

The discovery of a fourth immunoglobulin (Ig) light (L) chain isotype in sharks has revealed the origins and natural history of all vertebrate L chains. Phylogenetic comparisons have established orthology between this new shark L chain and the unique Xenopus L chain isotype sigma. More importantly, inclusion of this new L chain family in phylogenetic analyses showed that all vertebrate L chains can be categorized into four ancestral clans originating prior to the emergence of cartilaginous fish: one restricted to elasmobranchs (sigma-cart/type I), one found in all cold-blooded vertebrates (sigma/teleost type 2/elasmobranch type IV), one in all groups except bony fish (lambda/elasmobranch type II), and one in all groups except birds (kappa/elasmobranch type III/teleost type 1 and 3). All four of these primordial L chain isotypes (sigma, sigma-cart, lambda and kappa) have maintained separate V region identities since their emergence at least 450 million years ago, suggestive of an ancient physiological distinction of the L chains. We suggest that, based upon unique, discrete sizes of complementarity determining regions 1 and 2 and other features of the V region sequences, the different L chain isotypes arose to provide different functional conformations in the Ig binding site when they pair with heavy chains.

Preliminary investigation of 2-methoxyestradiol inducing differentiation of myeloma cell line CZ-1

This study was aimed to investigate whether 2-methoxyestradiol (2ME2) could exert effect of inducing differentiation on myeloma cells. A myeloma cell line CZ-1 secreting lambda light chain protein was used as an object of study. The CZ-1 cell morphology was observed by Wright's staining, the CD49e expression on cell surface after treatment with 2ME2 was detected by flow cytometry, the concentration of lambda light chain protein in the supernatant was assayed by immuno-scattering turbidity method. The results showed that treatments with 0.1-0.5 micromol/L 2ME2 for 72 hours resulted in some mature morphological changes of CZ-1 cells, such as the ratio of karyoplasms going down, nucleolus reducing or disappearing, chromatin getting rougher and more compacted; the CD49e positive CZ-1 cells increased by 2ME2 with concentrations of 0.1 micromol/L to 0.5 micromol/L in a concentration-dependent manner. The statistical difference from the control group was significant; the concentration of lambda light chain protein increased from control group 29.3 +/- 2.77 microg/ml to 35.97 +/- 2.6 microg/ml (P < 0.05) after exposure to 0.1 micromol/L 2ME2 for 72 hours, and the treatment of 0.5 micromol/L 2ME2 up-regulated lambda light chain protein to 79.67 +/- 1.88 microg/ml (P < 0.01) continuously. It is concluded that 2ME2 at low-concentration can induce differentiation of the CZ-1 cells to mature, which provides a new, and safe strategy for myeloma therapy.

Fatal HHV-8-Associated Hemophagocytic Syndrome in an HIV-Negative Immunocompetent Patient With Plasmablastic Variant of Multicentric Castleman Disease (Plasmablastic Microlymphoma)

Virus-associated hemophagocytic syndrome (VAHS) triggered by HHV-8 is extremely rare and has been reported only in 9 immunocompromised patients. We report the first case of HHV-8-associated VAHS in an HIV-negative, immunocompetent patient with plasmablastic variant (plasmablastic microlymphoma) of multicentric Castleman disease (MCD). This 61-year-old man presented with fever, cough, and bilateral inguinal lymphadenopathy. Biopsy of the right inguinal lymph node revealed plasmablastic MCD with nodular aggregates of plasmablasts expressing IgM, MUM1, HHV-8 latency-associated nuclear antigen, and viral interleukin-6. These plasmablasts were monotypic for Iglambda light chain expression but not Igkappa. All the B-cell clonality assays, including IgH-FR2, IgH-FR3, DH-JH, Igkappa, and Iglambda PCR, showed a polyclonal pattern. His serum human interleukin-6 level was markedly elevated and was negative for EBV acute infection/reactivation. The marrow aspirate showed florid hemophagocytosis. His disease progressed rapidly to multisystemic illness, and he died of acute respiratory failure in 1 month. Our case showed that HHV-8 might trigger VAHS in an immunocompetent patient with plasmablastic MCD. We speculated that our patient developed VAHS under the cytokine storm associated with the proliferating HHV-8-infected plasmablasts, similar to the EBV-triggered VAHS in patients with EBV-associated T-cell lymphoma.

Unusually similar patterns of antibody V segment diversity in distantly related marsupials

A pattern of coevolution between the V gene segments of Ig H and L chains has been noted previously by several investigators. Species with restricted germline V(H) diversity tend to have limited germline V(L) diversity, whereas species with high levels of germline V(H) diversity have more diverse V(L) gene segments. Evidence for a limited pool of V(H) but diverse V(L) gene segments in a South American opossum, Monodelphis domestica, is consistent with this marsupial being an exception to the pattern. To determine whether M. domestica is unique or the norm for marsupials, the V(H) and V(L) of an Australian possum, Trichosurus vulpecula, were characterized. The Ig repertoire in T. vulpecula is also derived from a restricted V(H) pool but a diverse V(L) pool. The V(L) gene segments of T. vulpecula are highly complex and contain lineages that predate the separation of marsupials and placental mammals. Thus, neither marsupial follows a pattern of coevolution of V(H) and V(L) gene segments observed in other mammals. Rather, marsupial V(H) and V(L) complexity appears to be evolving divergently, retaining diversity in V(L) perhaps to compensate for limited V(H) diversity. There is a high degree of similarity between the V(H) and V(L) in M. domestica and T. vulpecula, with the majority of V(L) families being shared between both species. All marsupial V(H) sequences isolated so far form a common clade of closely related sequences, and in contrast to the V(L) genes, the V(H) likely underwent a major loss of diversity early in marsupial evolution.

Analysis of marginal zone B cell development in the mouse with limited B cell diversity: role of the antigen receptor signals in the recruitment of B cells to the marginal zone

The quasimonoclonal (QM) mouse provides an intelligible model to analyze the B cell selection as the competition between two major 4-hydroxy-3-nitrophenylacetyl-specific B cell populations whose BCR are comprised of the knockin V(H)17.2.25 (V(H)T)-encoded H chain and the lambda1 or lambda2 L chain. In this study, we show the QM system is useful to examine how BCR signals guide a subset of B cells to the marginal zone (MZ). Compared with the control C57BL/6 mice, the QM mice had approximately 2.7-fold increased number of B cells exhibiting the MZ B cell phenotype and a larger MZ area in the spleen. Interestingly, V(H)T/lambda2 B cells significantly predominated over V(H)T/lambda1 B cells in MZ-(V(H)T/lambda1:V(H)T/lambda2 approximately 3:7) and transitional 2-B cell subsets, while these two populations were comparable in immature, transitional 1, and mature counterparts. Thus, the biased use of lambda2 in the MZ B cells may be the result of selection in the periphery. The enlargement of MZ B cell compartment and the preferred recruitment of the V(H)T/lambda2 B cells were further augmented by doubling the V(H)T gene, but dampened by the dysfunction of Bruton's tyrosine kinase, suggesting a positive role of BCR signaling in this selection. Comparison of Ag specificity between V(H)T/lambda1 and V(H)T/lambda2 IgM mAbs revealed a polyreactive nature of the V(H)T/lambda2 BCR, including the reactivity with ssDNA. Taken together, it is suggested that polyreactivity (including self-reactivity) of BCR is crucial in driving B cells to differentiate into the MZ phenotype.

BASH-deficient mice: limited primary repertoire and antibody formation, but sufficient affinity maturation and memory B cell generation, in anti-NP response

Signaling through the B cell antigen receptor (BCR) induces activation and proliferation of B cells, a response that requires the adaptor protein BASH (also known as BLNK/SLP-65). Although BASH and other molecules, such as Btk, PLCgamma2 and PKCbeta, are known to be essential for T cell-independent immune responses in vivo, their requirement during T cell-dependent immune responses, especially their role in antibody affinity-maturation and memory B cell generation remains unclear. In this study, we examined primary and memory immune responses to the T cell-dependent hapten antigen, (4-hydroxy-3-nitrophenyl)acetyl (NP) conjugated to chicken gammaglobulin (CGG), in BASH-deficient mice on a C57BL/6 background. In the primary response, NP-specific IgM was barely produced and the typical anti-NP IgG1/lambda production was markedly attenuated, but kappa chain was unexpectedly over-represented in the anti-NP antibodies. In contrast, CGG-specific IgG1 was normally produced. In the memory response, IgG1/lambda antibody with high affinity to NP was produced at normal level in the mutant mice. The frequency and distribution of somatic mutations in the V(H)186.2 genes of the anti-NP IgG1/lambda antibody were also normal. These results indicate that BASH-mediated BCR signaling is dispensable for somatic hypermutation and affinity selection, as well as generation and response of memory B cells. Interestingly, mutated V(H) genes with the same clonal origin were prominent in the anti-NP antibodies of BASH-deficient mice, indicating that a limited number of original clones had been recruited into the memory compartment. Thus, the scarcity of specific clones in the primary repertoire and an impaired primary response is not detrimental to the quality and quantity of a memory response.

Cellular maturation defects in Bruton's tyrosine kinase-deficient immature B cells are amplified by premature B cell receptor expression and reduced by receptor editing

In the mouse, Bruton's tyrosine kinase (Btk) is essential for efficient developmental progression of CD43(+)CD2(-) large cycling into CD43(-)CD2(+) small resting pre-B cells in the bone marrow and of IgM(high) transitional type 2 B cells into IgM(low) mature B cells in the spleen. In this study, we show that the impaired induction of cell surface changes in Btk-deficient pre-B cells was still noticeable in kappa(+) immature B cells, but was largely corrected in lambda(+) immature B cells. As lambda gene rearrangements are programmed to follow kappa rearrangements and lambda expression is associated with receptor editing, we hypothesized that the transit time through the pre-B cell compartment or receptor editing may affect the extent of the cellular maturation defects in Btk-deficient B cells. To address this issue, we used 3-83 mu delta transgenic mice, which prematurely express a complete B cell receptor and therefore manifest accelerated B cell development. In Btk-deficient 3-83 mu delta mice, the IgM(+) B cells in the bone marrow exhibited a very immature phenotype (pre-BCR(+)CD43(+)CD2(-)) and were arrested at the transitional type 1 B cell stage upon arrival in the spleen. However, these cellular maturation defects were largely restored when Btk-deficient 3-83 mu delta B cells were on a centrally deleting background and therefore targeted for receptor editing. Providing an extended time window for developing B cells by enforced expression of the antiapoptotic gene Bcl-2 did not alter the Btk dependence of their cellular maturation. We conclude that premature B cell receptor expression amplifies the cellular maturation defects in Btk-deficient B cells, while extensive receptor editing reduces these defects.

Function of Bruton's tyrosine kinase during B cell development is partially independent of its catalytic activity

The Tec family member Bruton's tyrosine kinase (Btk) is a cytoplasmic protein tyrosine kinase that transduces signals from the pre-B and B cell receptor (BCR). Btk is involved in pre-B cell maturation by regulating IL-7 responsiveness, cell surface phenotype changes, and the activation of lambda L chain gene rearrangements. In mature B cells, Btk is essential for BCR-mediated proliferation and survival. Upon BCR stimulation, Btk is transphosphorylated at position Y551, which promotes its catalytic activity and subsequently results in autophosphorylation at position Y223 in the Src homology 3 domain. To address the significance of Y223 autophosphorylation and the requirement of enzymatic activity for Btk function in vivo, we generated transgenic mice that express the autophosphorylation site mutant Y223F and the kinase-inactive mutant K430R, respectively. We found that Y223 autophosphorylation was not required for the regulation of IL-7 responsiveness and cell surface phenotype changes in differentiating pre-B cells, or for peripheral B cell differentiation. However, expression of the Y223F-Btk transgene could not fully rescue the reduction of lambda L chain usage in Btk-deficient mice. In contrast, transgenic expression of kinase-inactive K430R-Btk completely reconstituted lambda usage in Btk-deficient mice, but the defective modulation of pre-B cell surface markers, peripheral B cell survival, and BCR-mediated NF-kappaB induction were partially corrected. From these findings, we conclude that: 1) autophosphorylation at position Y223 is not essential for Btk function in vivo, except for regulation of lambda L chain usage, and 2) during B cell development, Btk partially acts as an adapter molecule, independent of its catalytic activity.

Cutting edge: signaling and cell surface expression of a mu H chain in the absence of lambda 5: a paradigm revisited

Pre-B cell receptor (pre-BCR) signals are essential for pro-B cells to mature efficiently into pre-B cells. The pre-BCR is an Ig-like transmembrane complex that is assembled from two mu H chains (mu HC) and two surrogate L chains consisting of the non-covalently associated polypeptides VpreB and lambda5. In lambda5(-/-) mice, pro-B cell maturation is impaired, but not completely blocked, implying that a mu HC induces differentiation signals in the absence of lambda5. Using a mouse model, in which transgenic mu HC expression can be controlled by tetracycline, we show that in the absence of lambda5, the transgenic mu HC promotes in vivo differentiation of pro-B cells, induces IL-7-dependent cell growth, and is expressed on the surface of pre-B cells. Our findings not only show that an incomplete pre-BCR can initiate signals, but also challenge the paradigm that an IgHC must associate with an IgLC or a SLC to gain transport and signaling competency.

B Lymphocyte Development in Rabbit: Progenitor B Cells and Waning of B Lymphopoiesis

In mammals that use gut-associated lymphoid tissues for expansion and somatic diversification of the B cell repertoire, B lymphopoiesis occurs early in ontogeny and does not appear to continue throughout life. In these species, including sheep, rabbit, and cattle, little is known about the pathway of B cell development and the time at which B lymphopoiesis wanes. We examined rabbit bone marrow by immunofluorescence with anti-CD79a and anti-mu and identified both proB and preB cells. The proB cells represent the vast majority of B-lineage cells in the bone marrow at birth and by incorporation of 5-bromo-2'-deoxyuridine, they appear to be a dynamic population. PreB cells reach maximum levels in the bone marrow at 3 wk of age, and B cells begin to accumulate at 7 wk of age. We cloned two VpreB and one lambda5 gene and demonstrated that they are expressed within B-lineage cells in bone marrow. VpreB and lambda5 coimmunoprecipitated with the mu-chain in lysates of 293T cells transfected with VpreB, lambda5, and mu, indicating that VpreB, lambda5, and mu-chains associate in a preB cell receptor-like complex. By 16 wk of age, essentially no proB or preB cells are found in bone marrow and by PCR amplification, B cell recombination excision circles were reduced 200-fold. By 18 mo of age, B cell recombination excision circles were reduced 500- to 1000-fold. We suggest that B cell development in the rabbit occurs primarily through the classical, or ordered, pathway and show that B lymphopoiesis is reduced over 99% by 16 wk of age.

Antibody repertoire development in fetal and neonatal piglets. VI. B cell lymphogenesis occurs at multiple sites with differences in the frequency of in-frame rearrangements

B cell lymphogenesis in mammals occurs in various tissues during development but it is generally accepted that it operates by the same mechanism in all tissues. We show that in swine, the frequency of in-frame (IF) VDJ rearrangements differs among yolk sac, fetal liver, spleen, early thymus, bone marrow, and late thymus. All VDJ rearrangements recovered and analyzed on the 20th day of gestation (DG20) from the yolk sac were 100% IF. Those recovered at DG30 in the fetal liver were >90% IF, and this predominance of cells with apparently a single IF rearrangement continued in all organs until approximately DG45, which corresponds to the time when lymphopoiesis begins in the bone marrow. Thereafter, the proportion of IF rearrangements drops to approximately 71%, i.e., the value predicted whether VDJ rearrangement is random and both chromosomes were involved. Unlike other tissues, VDJs recovered from thymus after DG50 display a pattern suggesting no selection for IF rearrangements. Regardless of differences in the proportion of IF rearrangements, we observed no significant age- or tissue-dependent changes in CDR3 diversity, N region additions, or other characteristics of fetal VDJs during ontogeny. These findings indicate there are multiple sites of B cell lymphogenesis in fetal piglets and differences in the frequency of productive VDJ rearrangements at various sites. We propose the latter to result from differential selection or a developmentally dependent change in the intrinsic mechanism of VDJ rearrangement.

Comparative analysis of light chain expression in germinal center cells and mantle cells of reactive lymphoid tissues. A four-color flow cytometric study

We studied skewing of light chain ratios (LCRs) in germinal center cells (GCCs) relative to mantle cells (MCs) by flow cytometry (FC) in 98 reactive lymphoid tissues. LCRs were assessed using a 4-color lambda/kappa/CD20/CD38 tube. GCCs and MCs were discriminated by CD20 and CD38 density. Of 98 cases, 65 contained distinct GCCs and MCs. Light chain expression usually was dimmer on GCCs than on MCs; in 22 cases, the kappa and lambda clusters converged and accurate LCRs could not be determined. Of the remaining 43 cases, the mean GCC LCR was 1.78 (range, 1.10-3.07) vs 1.56 (range, 1.00-2.24) in the MCs (P = .001). The overall kappa/lambda ratio in cases containing GCCs and MCs was 1.65 (range, 1.18-2.69) compared with 1.46 (range, 1.00-1.98) in cases containing MCs only. Of 43 cases, 19 (44%) showed differences of 20% or more between the LCRs of GCCs and MCs. LCRs of GCCs and MCs may differ substantially in reactive lymphoid tissues. These subsets may form distinct clusters and skews in their LCRs and should not be misinterpreted as evidence of occult lymphoma.

B cell selection and affinity maturation during an antibody response in the mouse with limited B cell diversity

The quasi-monoclonal mouse has limited B cell diversity, whose major (approximately 80%) B cell Ag receptors are comprised of the knockin V(H) 17.2.25 (V(H)T)-encoded H chain and the lambda1 or lambda2 L chain, thereby being specific for 4-hydroxy-3-nitrophenylacetyl. The p-nitrophenylacetyl (pNP) was found to be a low affinity analog of nitrophenylacetyl. We examined affinity maturation of anti-pNP IgG by analyzing mAbs obtained from quasi-monoclonal mice that were immunized with this low affinity Ag. The results are: 1) Although V(H)T/lambda1 and V(H)T/lambda2 IgM were equally produced, V(H)T/lambda2 IgG almost exclusively underwent affinity maturation toward pNP. 2) A common mutation in complementarity-determining region 3 of V(H)T (T313A) mainly contributed to generating the specificity for pNP. 3) Because mutated V(H)T-encoded gamma-chains could form lambda1-bearing IgG in Chinese hamster ovary cells, apparent absence of V(H)T/lambda1 anti-pNP IgG may not be due to the incompatibility between the gamma-chains and the lambda1-chain, but may be explained by the fact that V(H)T/lambda1 B cells showed 50- to 100-fold lower affinity for pNP than V(H)T/lambda2 B cells. 4) Interestingly, a pNP-specific IgM mAb that shared common mutations including T313A with high affinity anti-pNP IgG was isolated, suggesting that a part of hypermutation coupled with positive selection can occur before isotype switching. Thus, even weak B cell receptor engagement can elicit an IgM response, whereas only B cells that received signals stronger than a threshold may be committed to an affinity maturation process.

The antisense approach in amyloid light chain amyloidosis: identification of monoclonal Ig and inhibition of its production by antisense oligonucleotides in in vitro and in vivo models

Primary amyloid L chain (AL) amyloidosis is a plasma cell disorder in which depositions of AL cause progressive organ failure. The lack of effective therapies for this fatal disease prompts exploration of newer treatment avenues. We have investigated the application of antisense oligonucleotides (AS) for the inhibition of monoclonal Ig production. The monoclonal L chain was identified by using primers designed for amplifying the human lambda Ig V (Vlambda) region. We demonstrated that AS against L chain complementarity-determining regions inhibited the production of L chain in vitro. RPMI 8226 myeloma cells injected in SCID mice developed s.c. tumors. RT-PCR analysis showed Vlambda mRNA expression in the tumors. In addition, the presence of human Ig in the sera of mice given injection of RPMI 8226 cells was confirmed by ELISA. Administration of AS inhibited the expression of Vlambda mRNA in the s.c. tumors and decreased the concentration of L chain in serum. Therefore, we have shown that it is possible to determine the sequence of Vlambda mRNA and design specific complementary oligonucleotides, suggesting that treatment with Vlambda antisense could represent a rational novel approach to improve treatment outcome in AL amyloidosis.

Detection of kappa- and lambda-expressing cells in the endometrium by in situ hybridization

The detection of kappa- and lambda-expressing cells in endometrial biopsies using in situ hybridization was correlated with the histologic findings. Forty endometrial biopsies were examined in conjunction with kappa and lambda expression in serial sections, recorded as the number of positive cells per 10 x100 fields. Cells expressing kappa or lambda were found in 39/40 (98%) biopsies with the average total number per 10 x100 fields as follows: proliferative (n = 13) 13; secretory (n = 6) 16; endometritis (n = 6) 623; polyp (n = 4) 72; adenocarcinoma (n = 6) 677; oral contraceptive effect (n = 5) 8. Many of the B lymphocytes expressing kappa and lambda did not have the cytologic features of plasma cells. The diagnosis of chronic endometritis can be made when the histologic findings of out-of-phase endometrial glands and focal fibrosis are seen with increased plasma cells; in cases where the latter is equivocal, in situ hybridization testing for light chain expression can be useful. Cells expressing kappa and lambda mRNA are relatively common in normally cycling endometrium, implying that mild chronic antigenic stimulation is present in most endometrial tissues. In situ hybridization for light chain expression can be helpful in endometria where only very rare plasma cells are seen; a baseline result would rule out chronic endometritis.

[Co-expression of immunoglobulin light chain kappa and lambda in gastric carcinoma cell]

OBJECTIVE

To study the expression of immunoglobulin light chain kappa and lambda (Igkappa and Iglambda) in gastric carcinoma cell and their co-expression.

METHODS

Igkappa and Iglambda of 22 human gastric carcinoma specimens embedded in paraffin were monitored through immunohistochemical method-LSAB method.

RESULTS

Among 22 gastric carcinoma specimens, both Igkappa and Iglambda were positive in 17 (77.3%), only Igkappa was positive in 2 (9.1%), only Iglambda was positive in 1 (4.5%), both Igkappa and Iglambda negative in 2 (9.1%). The expression of Igkappa and Iglambda in human gastric carcinoma cell showed significant close correlation (chi(2) = 5.49, P < 0.05).

CONCLUSION

Co-expression of immunoglobulin light chain kappa and lambda in gastric carcinoma cell is common, which suggests that the activation mechanism of immunoglobulin gene in gastric carcinoma cell may be different from that in B-lymphocytes. Study on co-expression of immunoglobulin light chain kappa and lambda in gastric carcinoma is promising.

Generation and characterization of human monoclonal scFv antibodies against Helicobacter pylori antigens

Infection with Helicobacter pylori is chronic despite a vigorous cellular and humoral immune response and causes severe pathology in some patients. In this study, phage display was used as a new approach in order to investigate the role of the host's humoral immune response in the pathogenesis of H. pylori gastritis. Human monoclonal single-chain Fv (scFv) antibody fragments against H. pylori cell lysate and the H. pylori urease were isolated from an immune phage display library, constructed from peripheral blood lymphocytes of an H. pylori-infected patient. After affinity selection, 23% of the clones tested showed binding activity against a lysate of the H. pylori Sydney strain in enzyme-linked immunosorbent assay (ELISA) and 9% bound the H. pylori urease. Further characterization by PCR-fingerprint analysis and sequencing revealed that two closely related H. pylori binders and one antiurease scFv could be isolated. The selected scFvs were highly specific as analyzed by ELISA and immunoblots using various bacterial lysates and recombinant proteins. Analysis of the humoral immune response following H. pylori infection using human monoclonal antibodies might contribute to a better understanding of the pathogenesis of the disease. Moreover, using immune phage display libraries, it might be possible for relevant epitopes of H. pylori antigens to be determined, which might be of use for vaccine development.

Biased Iglambda expression in hypermutated IgD multiple myelomas does not result from receptor revision

Normal IgM(-)IgD(+) CD38(+) B cells and IgM(-)IgD(+) multiple myelomas (MM) are characterized by Cmu deletion, biased Iglambda expression and hypermutated IgV regions. The predominant Iglambda usage has been proposed as resulting from secondary Ig gene rearrangements during extensive clonal expansion in the germinal center environment. Here, four cases of IgDlambda MM were studied to address the question of light chain receptor revision in a 'single cell' model. Detailed analyses of both IGK and IGL alleles of each case were performed by Southern blotting, (RT-) PCR, and sequencing. The expressed IgV genes were extensively mutated and Cmu deletion was confirmed in two cases. In addition, in the four MM a total of six non-functional deletional IGK rearrangements were identified, which proved to be unmutated. We conclude that IgD myelomas indeed originate from (post) germinal center B cells in which, in spite of the fact that they are hypermutated, there is no evidence of receptor revision.

Chronic graft-versus-host in Ig knockin transgenic mice abrogates B cell tolerance in anti-double-stranded DNA B cells

Anti-dsDNA Abs are specific diagnostic markers of systemic lupus erythematosus, and are also implicated in kidney pathology. Anti-dsDNA B cells have been shown to be tolerized in nonautoimmune mice. The immunodysregulation that causes these cells to break tolerance is presumably part of the fundamental defects in systemic lupus erythematosus. To explore these mechanisms, we used the chronic graft-versus-host model mediated by MHC class II differences. Induction of chronic graft-vs-host in anti-DNA H chain knockin (3H9.KI) transgenic mice on a nonautoimmune background resulted in specific activation of anti-dsDNA B cells, as evidenced by high titers of soluble Ab in sera and a high frequency (70%) of anti-dsDNA B cell clones recovered as hybridomas. In addition, the lambda(+)-anti-dsDNA B cells developed increased expression of cell surface activation markers, and concentrated in the T cell area of the follicle with an Ab-forming cell-compatible phenotype. Genetic analysis of the hybridoma clones showed strong evidence of secondary rearrangements of the L chain associated with anti-dsDNA reactivity. Thus, our study indicates that alloreactive T cell help can break tolerance in a complex manner, involving several events.

Regulation of human Ig lambda light chain gene expression by NF-kappa B

The human Iglambda enhancer consists of three separated sequence elements that we identified previously by mapping DNase I-hypersensitive regions (HSS) downstream of the C region of the Iglambda L chain genes (HSS-1, HSS-2, and HSS-3). It has been shown by several laboratories that expression of the H chain genes as well as the kappa genes, but not the lambda genes, is dependent on constitutive NF-kappaB proteins present in the nucleus. In this study we show by band-shift experiments, in vivo footprinting, and transient transfection assays that all three hypersensitive sites of the human Iglambda enhancer contain functional NF-kappaB sites that act synergistically on expression. We further show that the chicken lambda enhancer also contains a functional NF-kappaB site but the mouse lambda enhancer contains a mutated, nonfunctional NF-kappaB site that is responsible for its low enhancer activity. It is possible that the inactivating mutation in the mouse Iglambda enhancer was compensated for by an expansion of the Igkappa L chain locus, followed by a contraction of the Iglambda locus in this species.

Signaling through TNF receptor p55 in TNF-alpha-deficient mice alters the CXCL13/CCL19/CCL21 ratio in the spleen and induces maturation and migration of anergic B cells into the B cell follicle

The organization of secondary lymphoid tissues into distinct T and B cell compartments supports proper regulation of an immune response to foreign Ags. In the splenic white pulp, this compartmentalization is also thought to be important in the maintenance of B cell tolerance. Using lymphotoxin-alpha-(LT-alpha)-, TNF-alpha-, or TNFRp55-deficient mice, all with disrupted splenic architecture, we tested whether normal T/B segregation and/or intact follicular structure are necessary for the maintenance of anti-dsDNA B cell anergy. This study demonstrates that anti-dsDNA B cells remain tolerant in LT-alpha(-/-), TNF-alpha(-/-), and TNFRp55(-/-) mice; however, TNF-alpha or a TNF-alpha-dependent factor is required for their characteristic positioning to the T/B interface. Providing a TNF-alpha signal in TNF-alpha(-/-) mice by systemic administration of an agonist anti-TNFRp55 mAb induces the maturation of the anti-dsDNA B cells and their movement away from the T cell area toward the B cell area. Additionally, the agonist Ab induces changes in the follicular environment, including FDC clustering, up-regulation of the CXC chemokine ligand CXCL13, and down-regulation of the CC chemokine ligands CCL19 and CCL21. Therefore, this study suggests that a balance between B and T cell tropic chemokine signals may be an important mechanism for positioning anergic B cells at the T/B interface of the splenic white pulp.

Circulating human B cells that express surrogate light chains display a unique antibody repertoire

Circulating human B cells that coexpress V-preB and conventional L chains (V-preB+L+ B cells) are a recently described subset of B cells that express Abs with features of self-reactivity. Initial analysis of V-preB+L+ B cells was limited to Ig-kappa and to the small, underused VH5 family. To determine whether Abs commonly expressed by V-preB+L+ B cells show similar features, we analyzed Ig H chains from three highly expressed VH families, VH1, VH3, and VH4, and Ig-lambda. We find that VH1 and VH3 Abs expressed by V-preB+L+ B cells resemble VH5 in that they display increased JH6 use, long CDR3s, and an increased frequency of D-D fusions. Abs in all three of these VH families also show skewed D reading frame use resulting in predominance of hydrophobic amino acids, which are counterselected in conventional B cells. Like Ig-kappa genes, the Ig-lambda genes in V-preB+L+ B cells show long CDR3s, but they differ from Ig-kappa genes in that they display no evidence of receptor editing. We conclude that a large number of H and L chain Abs expressed by V-preB+L+ B cells display features associated with self-reactive Abs.

Decreased frequency of somatic hypermutation and impaired affinity maturation but intact germinal center formation in mice expressing antisense RNA to DNA polymerase zeta

To examine a role of DNA polymerase zeta in somatic hypermutation, we generated transgenic mice that express antisense RNA to a portion of mouse REV3, the gene encoding this polymerase. These mice express high levels of antisense RNA, significantly reducing the levels of endogenous mouse REV3 transcript. Following immunization to a hapten-protein complex, transgenic mice mounted vigorous Ab responses, accomplished the switch to IgG, and formed numerous germinal centers. However, in most transgenic animals, the generation of high affinity Abs was delayed. In addition, accumulation of somatic mutations in the V(H) genes of memory B cells from transgenic mice was decreased, particularly among those that generate amino acid replacements that enhance affinity of the B cell receptor to the hapten. These data implicate DNA polymerase zeta, a nonreplicative polymerase, in the process of affinity maturation, possibly through a role in somatic hypermutation, clonal selection, or both.

RAG1 and RAG2 expression by B cell subsets from human tonsil and peripheral blood

It has been suggested that B cells acquire the capacity for secondary V(D)J recombination during germinal center (GC) reactions. The nature of these B cells remains controversial. Subsets of tonsil and blood B cells and also individual B cells were examined for the expression of recombination-activating gene (RAG) mRNA. Semiquantitative analysis indicated that RAG1 mRNA was present in all tonsil B cell subsets, with the largest amount found in naive B cells. RAG2 mRNA was only found in tonsil naive B cells, centrocytes, and to a lesser extent in centroblasts. Neither RAG1 nor RAG2 mRNA was routinely found in normal peripheral blood B cells. In individual tonsil B cells, RAG1 and RAG2 mRNAs were found in 18% of naive B cells, 22% of GC founder cells, 0% of centroblasts, 13% of centrocytes, and 9% of memory B cells. Individual naive tonsil B cells containing both RAG1 and RAG2 mRNA were activated (CD69(+)). In normal peripheral blood approximately 5% of B cells expressed both RAG1 and RAG2. These cells were uniformly postswitch memory B cells as documented by the coexpression of IgG mRNA. These results indicate that coordinate RAG expression is not found in normal peripheral naive B cells but is up-regulated in naive B cells which are activated in the tonsil. With the exception of centroblasts, RAG1 and RAG2 expression can be found in all components of the GC, including postswitch memory B cells, some of which may circulate in the blood of normal subjects.

Baculovirus expression cassette vectors for rapid production of complete human IgG from phage display selected antibody fragments

For the expression of human intact IgG antibodies, we have constructed a set of baculovirus expression vectors designed to facilitate rapid insertion of heavy and light chain genes of Fab or scFv antibodies derived from phage display antibody libraries. By linking them to human constant or Fc regions, expression of complete human immunoglobulin molecules was achieved in insect cells by infection with recombinant baculovirus. The IgG expression cassette vectors are based on the backbone vector which contains two back to back polyhedron and p10 promoters. The IgG expression cassette elements, including the authentic IgG lambda or kappa and heavy chain signal sequences, as well as light chain (lambda or kappa) and heavy chain constant region genes are combined in a single vector and are controlled by the p10 and polyhedron promoter respectively. Either of VL or Fab-L and VH or Fab-Fd genes from common phage display systems can be directly inserted into one of the cassette vectors through in-frame cloning sites. This design of a single cassette vector combining heavy and light chain expression elements allowed rapid production and secretion of correctly processed and assembled intact immunoglobulins from recombinant baculovirus infected insect cells. The recombinant antibodies showed the expected molecular size of the H2L2 heterodimer in non reducing SDS-PAGE. No apparent differences were found between the expression level of heavy and light chains, and antigen binding function was preserved. For various antibodies, yields between 6 and 18 mg/l IgG were obtained.

The V lambda J lambda repertoire in human fetal spleen: evidence for positive selection and extensive receptor editing

VlambdaJlambda rearrangements obtained from genomic DNA of individual IgM(+) B cells from human fetal spleen were analyzed. A nonrandom pattern of lambda gene rearrangements that differed from the adult Vlambda repertoire was found. The Vlambda distal genes 8A and 4B were absent from the nonproductive fetal repertoire, whereas 2E and 3L were overrepresented and 1B was underrepresented in the productive fetal repertoire. Positive selection of the Vlambda gene, 2E, along with Vlambda rearrangements employing homologous VlambdaJlambda joins were observed in the fetal, but not in the adult Vlambda repertoire. Overrepresentation of Jlambda distal cluster C genes rearranging to the Vlambda distal J segment, Jlambda7, in both productive and nonproductive fetal repertoires suggested that receptor editing/replacement was more active in the fetus than in adults. Numerous identical VlambdaJlambda junctions were observed in both the productive and nonproductive repertoire of the fetus and adult, but were significantly more frequent in the productive repertoire of the fetus, suggesting expansion of B cells expressing particular lambda-light chains in both stages of development, with more profound expansion in the fetal repertoire. Notably, B cells expressing identical lambda-light chains expressed diverse heavy chains. These data demonstrate that three mechanisms strongly influence the shaping of the human fetal lambda-chain repertoire that are less evident in the adult: positive selection, receptor editing, and expansion of B cells expressing specific lambda-light chains. These events imply that the expressed fetal repertoire is shaped by exposure to self Ags.

A novel variant of B-lymphoid leukemia expressing kappa/lambda light chains

We studied a patient with an indolent leukemia which behaved similarly to chronic lymphocytic leukemia (CLL). Leukemic cells, however, showed larger cell diameters and lower nuclear/cytoplasmic ratios than typical CLL cells, and contained numerous cytoplasmic vacuoles. The cells also demonstrated some morphologic characteristics of hairy cell leukemia. Furthermore, flow-cytometric analysis demonstrated a distinct population of kappa/lambda double-positive tumor cells, as well as kappa single and lambda single populations. Southern blot analysis confirmed rearranged bands for both light chains with a monoclonal heavy chain rearrangement. Despite a decision not to treat this asymptomatic patient, disease progression was not observed. This case may represent a unique variant of B lymphoid leukemia. Possible mechanisms of abnormal light chain expression are discussed.

Double producers of kappa and lambda define a subset of B cells in mouse plasmacytomas

Rearrangement of the light chain locus is believed to be an ordered process in which Iglambda rearrangements only occur if Igkappa rearrangements are found to be non-productive or self-reactive. Secondary rearrangements of the B-cell receptor (BCR) have shown, however, that rescue of abortive Igkappa rearrangements or autoreactive B cells can be achieved through receptor editing using upstream V-regions as the template sequences. Since secondary rearrangement can occur in the periphery, possibly in a subset of B cells maintaining constitutive Rag activity, it is conceivable that two light chains (kappa:kappa or kappa:lambda) could be expressed in these cells, apparently in violation of allelic exclusion. Previously, we have reported that silicone-induced plasmacytomas (SIPCs) exhibit dual expression and ongoing rearrangements of Igkappa and Iglambda. In this paper, we show by ELISA that both Igkappa and Iglambda are found at the protein level, but are secreted in different amounts. Furthermore, we demonstrate by micro-manipulation and RT-PCR amplification that Igkappa and Iglambda are simultaneously expressed in a single SIPC cell. We propose that these dual-expressing cells, found intermittently in cases of plasmacytomas (PCs), may have originally been immature B cells when transformed but now are maintained as a long-lived mature B cell found infrequently in the tumor population.

Transgenic human lambda 5 rescues the murine lambda 5 nullizygous phenotype

The human lambda 5 (hu lambda 5) gene is the structural homologue of the murine lambda 5 (m lambda 5) gene and is transcriptionally active in pro-B and pre-B lymphocytes. The lambda 5 and VpreB polypeptides together with the Ig mu H chain and the signal-transducing subunits, Ig alpha and Ig beta, comprise the pre-B cell receptor. To further investigate the pro-B/pre-B-specific transcription regulation of hu lambda 5 in an in vivo model, we generated mouse lines that contain a 28-kb genomic fragment encompassing the entire hu lambda 5 gene. High levels of expression of the transgenic hu lambda 5 gene were detected in bone marrow pro-B and pre-B cells at the mRNA and protein levels, suggesting that the 28-kb transgene fragment contains all the transcriptional elements necessary for the stage-specific B progenitor expression of hu lambda 5. Flow cytometric and immunoprecipitation analyses of bone marrow cells and Abelson murine leukemia virus-transformed pre-B cell lines revealed the hu lambda 5 polypeptide on the cell surface and in association with mouse Ig mu and mouse VpreB. Finally, we found that the hu lambda 5 transgene is able to rescue the pre-B lymphocyte block when bred onto the m lambda 5-/- background. Therefore, we conclude that the hu lambda 5 polypeptide can biochemically and functionally substitute for m lambda 5 in vivo in pre-B lymphocyte differentiation and proliferation. These studies on the mouse and human pre-B cell receptor provide a model system to investigate some of the molecular requirements necessary for B cell development.

Affiliation to mature B cell repertoire and positive selection can be separated in two distinct processes

Using an 'oligoclonal' model, we have previously shown that mice transgenic for a mu chain (H3) and deficient for kappa chain expression display a mature B cell repertoire largely dominated by the H3/lambda1 pair, while the four H3/lambda available combinations can be observed in the immature B cell compartment. This led us to propose the existence of a positive selection process. To test this hypothesis, we have introduced the SJL lambda locus coding for a defective lambda1 chain (lambda1(s)) that creates a dysfunctional Ig receptor complex during B cell differentiation. Our results show that the lambda1(s) defect impairs the development of mature B cells when the H3-mu transgene insert is present in the hemizygous state. This suggests that the Gly --> Val substitution present in the C(lambda)1(s) chain at position 155 is sufficient to abrogate the selection of the H3/lambda1 pair. Unexpectedly, when the H3-mu transgene array is present in a homozygous state in lambda1(s) mice but not in 'wild-type' lambda1 mice (lambda1(+)), a significant number of mature B cells expressing all H3/lambda combinations can be developed. These results indicate that the overriding H3/lambda1 dominance observed in lambda1(+) mice is due to a positive selection process and not to a negative selection of other H3/lambda combinations. They also show that the export of B cells to the periphery can be controlled by the expression of the mu chain.

Murine pro-B cells require IL-7 and its receptor complex to up-regulate IL-7R alpha, terminal deoxynucleotidyltransferase, and c mu expression

Phenotypic analysis of bone marrow cells from IL-7 knockout (KO) mice revealed that B cell development is blocked precisely at the transition between pro-B cells and pre-B cells. In contrast, the generation of pre-pro-B cells and pro-B cells appeared to be normal, as judged by total cell numbers, proliferative indexes, D-JH and V-DJH gene rearrangements, and mRNA for recombinase-activating gene-1 (RAG-1), RAG-2, TdT, Ig mu, lambda 5, and VpreB. However, upon closer inspection, several abnormalities in pro-B cell development were identified that could be corrected by injection of rIL-7 in vivo. These included the absence of the subset of late pro-B cells that initiates cmu expression for pre-B cell Ag receptor (BCR) formation, and the failure of pro-B cells to up-regulate TdT and the IL-7R alpha (but not the common gamma-chain) chain. Similar defects were present in common gamma-chain and Jak3 KO mice, but not in lambda 5 or (excluding cytoplasmic Ig mu heavy chain (c mu)) RAG-1 KO mice, all of which also arrest at the late pro-B cell stage. Consequently, up-regulation of TdT and IL-7R alpha expression requires signaling through the high affinity IL-7R, but does not require cmu expression or a functional pre-BCR. Taken together, these results suggest that IL-7 and its receptor complex are essential for 1) up-regulating the expression of TdT and IL-7R alpha, 2) initiating the production of cmu and 3) promoting the formation of a functional pre-BCR in/on pro-B cells. These key events, in turn, appear to be prerequisite both for differentiation of pro-B cells to pre-B cells and for proliferation of these cell subsets upon continued stimulation with IL-7.

Roles of PLC-beta2 and -beta3 and PI3Kgamma in chemoattractant-mediated signal transduction

The roles of phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC) in chemoattractant-elicited responses were studied in mice lacking these key enzymes. PI3Kgamma was required for chemoattractant-induced production of phosphatidylinositol 3,4,5-trisphosphate [PtdIns (3,4,5)P3] and has an important role in chemoattractant-induced superoxide production and chemotaxis in mouse neutrophils and in production of T cell-independent antigen-specific antibodies composed of the immunoglobulin lambda light chain (TI-IglambdaL). The study of the mice lacking PLC-beta2 and -beta3 revealed that the PLC pathways have an important role in chemoattractant-mediated production of superoxide and regulation of protein kinases, but not chemotaxis. The PLC pathways also appear to inhibit the chemotactic activity induced by certain chemoattractants and to suppress TI-IglambdaL production.

Functional consequences of the developmental arrest and follicular exclusion of anti-double-stranded DNA B cells

Anti-dsDNA B cells are actively tolerized in nonautoimmune BALB/c mice, as manifested by their developmental arrest, follicular exclusion, and rapid turnover rate. Previously, we have documented changes in the maturation status and follicular localization of anti-dsDNA B cells in autoimmune-prone MRL (+/+ and lpr/lpr) mice. To determine whether these differences in developmental status and follicular localization affect the functional capacity of anti-dsDNA B cells, we have now compared their in vivo life spans and their responses to in vitro stimuli. Our study shows that although anti-dsDNA B cells from both BALB/c and MRL-+/+ mice are localized to the T/B interface, only those in BALB/c mice have a rapid turnover rate. Therefore, the immature status and not the exclusion from the B cell follicle correlates with a shortened life span. Interestingly, apoptotic anti-dsDNA B cells were not detected at the T/B interface in BALB/c mice, suggesting that they are not dying there. This study also demonstrates that anti-dsDNA B cells, regardless of maturation status or follicular localization, are able to proliferate and up-regulate the costimulatory molecule B7-2 in response to CD40 ligand and IL-4. Therefore, one of the critical in vivo differences between anti-dsDNA B cells in BALB/c and MRL-+/+ mice compared with MRL-lpr/lpr mice may be the availability of T cell help.

Antibody repertoires of four- and five-feature translocus mice carrying human immunoglobulin heavy chain and kappa and lambda light chain yeast artificial chromosomes

We have produced mice that carry the human Ig heavy (IgH) and both kappa and lambda light chain transloci in a background in which the endogenous IgH and kappa loci have been inactivated. The B lymphocyte population in these translocus mice is restored to about one-third of normal levels, with preferential (3:1) expression of human lambda over human kappa. Human IgM is found in the serum at levels between 50 and 400 microg/ml and is elevated following immunization. This primary human Ab repertoire is sufficient to yield diverse Ag-specific responses as judged by analysis of mAbs. The use of DH and J segments is similar to that seen in human B cells, with an analogous pattern of N nucleotide insertion. Maturation of the response is accompanied by somatic hypermutation, which is particularly effective in the light chain transloci. These mice therefore allow the production of Ag-specific repertoires of both IgM,kappa and IgM,lambda Abs and should prove useful for the production of human mAbs for clinical use.

Cloning the antibody response in humans with inflammatory central nervous system disease: analysis of the expressed IgG repertoire in subacute sclerosing panencephalitis brain reveals disease-relevant antibodies that recognize specific measles virus antigens

The presence of increased IgG in the brains of humans with infectious and inflammatory CNS diseases of unknown etiology such as multiple sclerosis may be a clue to the cause of disease. For example, the intrathecally synthesized oligoclonal bands (OGBs) in diseases such as subacute sclerosing panencephalitis (SSPE) or cryptococcal meningitis have been shown to represent Ab directed against the causative agents, measles virus (MV) or Cryptococcus neoformans, respectively. Using SSPE as a model system, we have developed a PCR-based strategy to analyze the repertoire of IgG V region sequences expressed in SSPE brain. We observed abnormal expression of germline V segments, overrepresentation of particular sequences that correspond to the oligoclonal bands, and substantial somatic mutation of most clones from the germline, which, taken together, constitute features of Ag-driven selection in the IgG response. Using the most abundant or most highly mutated gamma H chain and kappa or lambda L chain sequences in various combinations, we constructed functional Abs in IgG mammalian expression vectors. Three Abs specifically stained MV-infected cells. One Ab also stained cells transfected with the MV nucleoprotein, and a second Ab stained cells transfected with the MV-fusion protein. This technique demonstrates that functional Abs produced from putative disease-relevant IgG sequences can be used to recognize their corresponding Ags.

The importance of the light chain for the epitope specificity of human anti-U1 small nuclear RNA autoantibodies present in systemic lupus erythematosus patients

Abs to U1 RNA are frequently found in patients suffering from systemic lupus erythematosus overlap syndromes and Ab titers correlate with disease activity. We describe the isolation of the first human anti-U1 RNA autoantibodies from a combinatorial IgG library made from the bone marrow of a systemic lupus erythematosus patient. With the use of phage display technology, two anti-U1 RNA single-chain variable fragment (scFv) Abs were selected. Both high affinity anti-U1 RNA Ab fragments (Kd approximately 1 nM) recognize stem II of U1 RNA and were derived from the same heavy chain gene (VH3-11) and the same lambda (3r) light chain gene although somatic mutations, predominantly present in the complementarity-determining regions, are different. Experiments, in which the heavy chain genes of both anti-U1 RNA scFvs were reshuffled with the original light chain repertoire of the patient resulted, after selection on stem loop II, in a large number of RNA-binding Ab fragments. All these stem loop II-specific RNA binding clones used a similar, but not identical, 3r lambda light chain. When scFvs were selected from the reshuffled libraries by stem loop IV, representing the other autoantigenic site of U1 RNA, most selected Ab clones did react with stem loop IV, but no longer with stem loop II. The stem loop IV-reactive Ab clones contained different, not 3r-related, light chains. These results point to a major role for the light chain in determining the sequence specificity of these disease-related anti-U1 RNA Abs. The possibility that secondary light chain rearrangements are involved in this autoimmune response is discussed.

Aberrant antigen expression detected by multiparameter three color flow cytometry in intermediate and high grade B-cell lymphomas

The aberrant expression of antigens (Ag) in lymphoproliferative disorders may cause a diagnostic problem when single parameter immunohistochemical assays are performed on frozen or paraffin sections because coexpression by relevant cells is not determined. This aberrant expression also raises the question as to whether mixed lineage (biphenotypic) lymphoid proliferations exist. Marrow (6) and extramedullary (20) tissues from 26 patients with diffuse, intermediate and high grade, B-cell lymphomas (IWF E=1, F=1, G=19, H=1 and J=4) were analyzed with 19 markers using 3-color flow cytometry. The percentages (%) of patients with double Ag coexpression in at least 20% of the CD19+ or CD20+ lymphoma cells were: stem cell (SC) Ag: CD10 = 58 and CD34 = 15; T-cell Ag: CD2 = 38, CD5 = 19 and CD7 = 19; myeloid (My) Ag: CD13 = 19 and CD33 = 8. The corresponding % with unusual triple Ag coexpression in at least 10% of the CD19+ B-cells were SC+T+ Ag: CD10CD2 = 50, CD10CD5 = 27, CD10CD7 = 38, CD34CD2 = 31, CD34CD5 = 19 and CD34CD7 = 27; T+T+ Ag: CD2CD5 = 35, CD2CD7 = 42 and CD5CD7 = 31; T+My+ Ag: CD2CD13 = 35 and CD2CD33 = 12; and My+My+ Ag: CD13CD33 = 12. Ten of 12 lymphomas tested showed clonal immunoglobulin (Ig) heavy chain gene rearrangements in the absence of clonal T-cell receptor (TCR) gene rearrangements. None (0%) of the My Ag positive cases showed immunoreactivity for myeloperoxidase. We conclude that the anomalous T and My Ag expression seen in the above B-cell lymphomas is not indicative of mixed lineage proliferation but represents the aberrant expression of these antigens by the malignant cells.

Monoclonal autoantibodies from patients with autoimmune diseases: synovial fluid B lymphocytes of a patient with rheumatoid arthritis produced an IgG lambda antibody recognizing J-sequences of Ig kappa chains in a conformation-dependent way

Synovial fluid B cells from a patient with seronegative rheumatoid arthritis were immortalized by electrofusion. The specificity of clone FKN-E12 (IgG1 lambda) was analysed by screening a phage display random peptide library. One heptamer sequence was identified (RASFp1 = HLTFGPG). Three human IgG kappa antibodies contained a highly homologous sequence (xLTFGPG) at the junction of V- and J-regions. Homologies were also found in distinct humans (J kappa 3, J kappa 4) and murine (J kappa 5) J kappa-sequences (TFGPG, LTFGxG), and to a lower degree in all remaining J kappa-sequences (TFGxG). Binding and binding inhibition assays showed that FKN-E12 bound to kappa light chains tested in a conformation-dependent way: it reacted only with IgG kappa or IgA kappa chains adhered to a plastic surface, but not in soluble form. In conclusion, FKN-E12 detects a conformational epitope on probably all kappa light chains, which could be definded by screening a phage library displaying linear epitopes.

Organ-specific (localized) synthesis of Ig light chain amyloid

Ig amyloidosis is usually a systemic disease with multisystem involvement. However, in a significant number of cases amyloid deposition is limited to one specific organ. It has not been determined if the Ig light chain (LC) amyloid precursor protein in localized amyloidosis is synthesized by circulating plasma cells with targeting of the amyloid fibril-forming process to one specific organ, or whether the synthesis of Ig LC and fibril formation occurs entirely as a localized process. In the present study local synthesis of an amyloid fibril precursor LC was investigated. Amyloid fibrils were isolated from a ureter that was obstructed by extensive infiltration of the wall with amyloid. Amino acid sequence analysis of the isolated fibril subunit protein proved it to be derived from a lambdaII Ig LC. Plasma cells within the lesion stained positively with labeled anti-lambda Ab and by in situ hybridization using an oligonucleotide probe specific for lambda-LC mRNA. RT-PCR of mRNA extracted from the tumor and direct DNA sequencing gave the nucleotide sequence coding specifically for the lambdaII amyloid subunit protein, thus confirming local synthesis of the LC protein.

Molecular mechanisms and selection influence the generation of the human V lambda J lambda repertoire

To define the lambda light chain repertoire in humans, a single-cell PCR technique using genomic DNA obtained from individual peripheral B cells was employed. Of the 30 known functional V lambda genes, 23 were detected in either the nonproductive or productive repertoires. Specific V lambda genes, including 2A2, 2B2, 1G, and 4B, were overexpressed in the nonproductive repertoire, whereas some V lambda genes, such as 3R, 2A2, 2B2, 1C, 1G, and 1B, were overexpressed in the productive repertoire. Comparison of the nonproductive and productive repertoires indicated that no V lambda genes were positively selected, whereas a number of V lambda genes, including 4C, 1G, 5B, and 4B, were negatively regulated. All four of the functional J lambda segments were found in both repertoires, with J lambda 7 observed most often. Evidence of terminal deoxynucleotidyltransferase activity was noted in nearly 80% of nonproductive V lambda J lambda rearrangements, and exonuclease activity was apparent in the majority. Despite this, the mean CDR3 length was 30 base pairs in both productive and nonproductive repertoires, suggesting that it was tightly regulated at the molecular level. These results have provided new insights into the dimensions of the human V lambda repertoire and the influences that shape it.

The in vivo association of BiP with newly synthesized proteins is dependent on the rate and stability of folding and not simply on the presence of sequences that can bind to BiP

Immunoglobulin heavy chain-binding protein (BiP) is a member of the hsp70 family of chaperones and one of the most abundant proteins in the ER lumen. It is known to interact transiently with many nascent proteins as they enter the ER and more stably with protein subunits produced in stoichiometric excess or with mutant proteins. However, there also exists a large number of secretory pathway proteins that do not apparently interact with BiP. To begin to understand what controls the likelihood that a nascent protein entering the ER will associate with BiP, we have examined the in vivo folding of a murine lambdaI immunoglobulin (Ig) light chain (LC). This LC is composed of two Ig domains that can fold independent of the other and that each possess multiple potential BiP-binding sequences. To detect BiP binding to the LC during folding, we used BiP ATPase mutants, which bind irreversibly to proteins, as "kinetic traps." Although both the wild-type and mutant BiP clearly associated with the unoxidized variable region domain, we were unable to detect binding of either BiP protein to the constant region domain. A combination of in vivo and in vitro folding studies revealed that the constant domain folds rapidly and stably even in the absence of an intradomain disulfide bond. Thus, the simple presence of a BiP-binding site on a nascent chain does not ensure that BiP will bind and play a role in its folding. Instead, it appears that the rate and stability of protein folding determines whether or not a particular site is recognized, with BiP preferentially binding to proteins that fold slowly or somewhat unstably.

Light chain shifting: identification of a human plasma cell line actively undergoing light chain replacement

We identified an antibody-secreting human B-cell line (HTD8), which actively replaces the production of the original lambda light chain with a new lambda chain (light chain shifting) at a high rate. Loss of the original rearranged lambda light chain occurs by significantly reducing the amount of transcript expressed. Expression of the new lambda chain, which replaces the original lambda chain, occurs by rearranging new VJ segments on a previously excluded allele. V lambda gene usage of these new rearrangements are biased toward Vlambda4, Vlambda6, and Vlambda10 families, which are known to be the least frequently used. In striking contrast to the plasma cell phenotype, recombination activating genes, RAG-1 and RAG-2, were expressed in the HTD8 cells and were shown to be necessary, but insufficient for inducing expression of the new lambda chain. These results suggest that human plasma cells have the potential to actively undergo light chain replacement.

Comparison of the cytotoxic effects of corticoids on the neoplastic B cells

Many clinical trials have been engaged to prove the benefits of new drugs in the treatment of hematological tumours. However, no real progress have occurred in diseases such as multiple myeloma, the association of melphalan and prednisone is still the mainstay of the treatment. During all these years, the family of glucocorticoids have not been totally studied. Their efficiency in the cure of lymphoid malignancies has been early recognised, but still to be based on their anti-inflammatory potency for the dosages. Only few works reported the comparison between members of this family. We demonstrate in this work, in vitro, with a cell line of medium sensibility and a B cell of tumoral origin grew up in our laboratory, that exists some differences in the anti-neoplastic potency of the more commonly used corticoids. If the order in which we can class these drugs is not surprising and empirically known, the importance of the differences observed need a special attention. We also found that these drugs might have stimulatory effects, at various degree in function of their concentrations, on the proliferation of the B cell lines. Theses side effects coupled to the efficiency variations of each corticoid present the need of paying more attention to the choice of the molecule implied in the chemotherapy.

Plural immunoglobulin synthesis in a single cell: an ultrastructural study of two cases with three M-proteins

Electrophoresis revealed two cases of malignant lymphoma that each contained three M-proteins (IgM lambda.lgG kappa.lgG lambda and IgM lambda.IgM kappa.lgG kappa) in the sera. To determine cellular origin of each M-protein, atypical lymphoid and plasmacytoid cells of both cases were examined by electron microscopy. Atypical lymphoid and plasmacytoid cells possessed rough endoplasmic reticula (RERs) in varying degrees, as seen by conventional electron microscopy, and showed double-stainability for plural antibodies against immunoglobulins following double stainings of immunoelectron microscopy using immunogold staining. Rabbit antibodies against human IgM, lgG, free kappa-light chain and free lambda-light chain were used for the immunoelectron microscopic staining. By the double staining method, plural immunoglobulins, IgM/IgG, IgM/free kappa, IgM/free lambda, IgG/free kappa, IgG/free lambda and free kappa/free lambda, were simultaneously detected in varying degrees in the Golgi area, RERs, and dense bodies of lymphoid and plasmacytoid cells. In conclusion, this study directly exhibited, through electron microscopy, that plural immunoglobulins were synthesized at the same time in a single cell, and that the process of immunoglobulin synthesis in the lymphoid and plasmacytoid cells was different from that in a normal B-cell.

Senescent BALB/c mice exhibit decreased expression of lambda5 surrogate light chains and reduced development within the pre-B cell compartment

Although senescent BALB/c mice (approximately 2 years old) have reduced numbers of small pre-B cells, early pre-B cells (CD43+CD25+B220+) are present in comparable numbers within the bone marrow of both young (3-6-month-old) and senescent BALB/c mice. The transition of CD43+ pre-B cells to the CD43- pre-B cell compartments is dependent on proliferation and clonal maturation dictated by the pre-B cell receptor (mu/lambda5/VpreB). In vivo, senescent CD43+B220+ pro-B/early pre-B cells demonstrated reduction of lambda5 mRNA, by RT-PCR analysis, and of both surface and cytoplasmic lambda5 protein. Decreased lambda5 protein expression was also seen among pro-B/pre-B cells derived from senescent bone marrow after stimulation in vitro with IL-7. We propose that diminished expression of the lambda5 surrogate light chain results in decreased pre-B cell receptor formation and contributes to reduced recruitment of nascent CD43+ pre-B cells into the CD43- large and small pre-B cell compartments.