Endogenous serum antibodies that interfere with a common thyroid hormone uptake assay: characterization and prevalence

We identified individuals whose serum contained a substance that produced falsely decreased thyroid hormone (T)-uptake values determined by the Emit (Syva) procedure. Investigation of this interference was prompted by identification of a patient with T-uptake values inconsistent with clinical assessment. IgG depletion and supplementation studies with this patient's serum suggested that the interference was due to endogenous antibodies with specificity for the thyroxine-glucose-6-phosphate dehydrogenase conjugate in the Emit T-uptake assay. The prevalence of the interference was examined by prospectively comparing routine Emit T-uptake values of 1710 patients' samples to T-uptake values obtained by another method. Discrepant samples were also assayed by a radioactive binding triiodothyronine-uptake assay. We identified eight samples that had falsely decreased T-uptake values by Emit, for an overall prevalence of 0.46%. Among 45 consecutive patients with a T-uptake value < 20%, five patients, or 11%, were falsely decreased by Emit and three of these were clearly due to an interfering IgG. We suggest that samples with abnormally low T-uptake values determined by the Emit method be confirmed by an alternative method.

Endogenous serum antibodies that interfere with a common thyroid hormone uptake assay: characterization and prevalence

We identified individuals whose serum contained a substance that produced falsely decreased thyroid hormone (T)-uptake values determined by the Emit (Syva) procedure. Investigation of this interference was prompted by identification of a patient with T-uptake values inconsistent with clinical assessment. IgG depletion and supplementation studies with this patient's serum suggested that the interference was due to endogenous antibodies with specificity for the thyroxine-glucose-6-phosphate dehydrogenase conjugate in the Emit T-uptake assay. The prevalence of the interference was examined by prospectively comparing routine Emit T-uptake values of 1710 patients' samples to T-uptake values obtained by another method. Discrepant samples were also assayed by a radioactive binding triiodothyronine-uptake assay. We identified eight samples that had falsely decreased T-uptake values by Emit, for an overall prevalence of 0.46%. Among 45 consecutive patients with a T-uptake value < 20%, five patients, or 11%, were falsely decreased by Emit and three of these were clearly due to an interfering IgG. We suggest that samples with abnormally low T-uptake values determined by the Emit method be confirmed by an alternative method.

Comparison of nonhuman primate antibodies against Haemophilus influenzae type b polysaccharide with human antibodies in oligoclonality and in vivo protective potency

Nonhuman primates are often used as a model for studying vaccines for humans. However, it is not always clear how closely the antibody responses in these species mimic human responses. Recent studies have characterized the human antibody response to Haemophilus influenzae type b (Hib) in great detail. In this study, we have compared the antibody response to Hib of humans with those of other primates. Studies of isoelectric points and V kappa subgroup usage show that, like humans, nonhuman primates produce oligoclonal antibodies. Also, monkey antibodies to the Hib polysaccharide are as protective as human antibodies in an in vivo model of Hib infection. Thus, we conclude that nonhuman primates produce antibodies to Hib polysaccharide that are structurally and functionally similar to human antibodies and are a good model for testing human vaccines.

Properties of human follicular dendritic cells purified with HJ2, a new monoclonal antibody

Follicular dendritic cells (FDC) are found in germinal centers and may play an important role in germinal center (GC) B cell development. However, very little is known about FDC because it is very difficult to obtain a pure preparation of FDC. To aid in the purification of human FDC, we produced a mouse monoclonal antibody named HJ2 that immunohistochemically stains FDC in various lymphoid tissues. Isolated HJ2+ cells obtained by flow cytometric cell sorting exhibit morphological features associated with FDC and display numerous FDC-associated surface markers, but do not express T cell and B cell markers. Taken together, these findings indicate that HJ2 binds FDC and can be used to purify human FDC. Phenotypic studies of purified FDC revealed that FDC express large amounts of the complement (C)-regulatory proteins CD46, CD55, and CD59. By deactivating C, these proteins may safeguard FDC from membranolysis by surface-bound C containing immune complexes. To begin studies of FDC function, we cultured purified FDC and found they survive for at least 2 weeks in vitro. Furthermore, FDC were potent stimulators of allogeneic peripheral blood mononuclear cells and a T cell line in mixed lymphocyte cultures, and on a cell basis, FDC were more active than B cells. The purification of functionally active human FDC should facilitate studying the role of FDC in B cell development within GC.

Comparison of naturally acquired and vaccine-induced antibodies to Haemophilus influenzae type b capsular polysaccharide

The objective of this study was to assess qualitative differences in the types of Haemophilus influenzae type B (Hib) capsular polysaccharide (polyribosylribitol phosphate [PRP]) antibodies induced in children 15 to 27 months of age by (i) natural exposure, (ii) PRP vaccine, and by (iii) PRP-diphtheria toxoid conjugate vaccine, (iv) PRP-group B Neisseria meningitidis outer membrane vesicle conjugate vaccine, and (v) Haemophilus type B oligosaccharide conjugate vaccine (HbOC). The highest levels of total Hib-PRP antibody measured by radioimmunoassay and immunoglobulin G (IgG) measured by enzyme-linked immunosorbent assay were seen after HbOC immunization. IgG1 Hib-PRP antibodies predominated in all groups, and there were no differences between the groups in the proportion of IgG and IgA Hib-PRP antibodies. However, the proportions of IgM differed significantly by group. The highest proportions of IgM occurred in naturally acquired antibody and after PRP vaccine, and the lowest proportion occurred after HbOC vaccine. IgG light-chain V kappa type alpha PRP antibody was present in all groups, and the level correlated with the total IgG Hib-PRP antibody level. Therefore, HbOC induced the highest concentrations of V kappa II type alpha PRP antibody, and the naturally acquired antibody group had the lowest levels. IgG light-chain V kappa III antibody levels were also highest in the HbOC group, but there was no correlation between V kappa III antibody levels and total amount of IgG Hib-PRP antibody. These data demonstrate qualitative differences in the antibody repertoires induced by natural exposure, the Hib-PRP vaccine, and each of the different Hib conjugate vaccines. We doubt that there are major differences in the protection afforded by these different antibody repertoires, because these differences do not appear to correlate with differences in protective efficacy in older children.

T cells within germinal centers are specific for the immunizing antigen

A normal antibody response to T cell-dependent Ag requires physical contact between Ag-specific B and T cells. Because such Ag-specific cells are rare in vivo, we sought to identify an in vivo site where they physically contact each other. We examined the Ag specificity of T cells in germinal centers (GC) in lymph nodes, where it is known that Ag-specific B cells proliferate and mature. We investigated the Ag specificity of GC T cells in situ by examining two characteristics: 1) expression of certain V alpha and V beta TCR families; and 2) incorporation of bromodeoxyuridine into T cell DNA after exposure to Ag as an index of Ag-induced proliferation. When GC were induced in mice with cytochrome c and myelin basic protein, the GC T cells were found to preferentially express V alpha 11 and V beta 8 TCR families, which are, respectively, the dominant TCR families in these two responses. Furthermore, GC T cells have proliferated upon exposure to the Ag that induced GC formation. Taken together, these results demonstrate that GC must recruit and retain Ag-specific T cells, thus implicating the GC as an in vivo site where Ag-specific T and B cells interact.

T cells within germinal centers are specific for the immunizing antigen

A normal antibody response to T cell-dependent Ag requires physical contact between Ag-specific B and T cells. Because such Ag-specific cells are rare in vivo, we sought to identify an in vivo site where they physically contact each other. We examined the Ag specificity of T cells in germinal centers (GC) in lymph nodes, where it is known that Ag-specific B cells proliferate and mature. We investigated the Ag specificity of GC T cells in situ by examining two characteristics: 1) expression of certain V alpha and V beta TCR families; and 2) incorporation of bromodeoxyuridine into T cell DNA after exposure to Ag as an index of Ag-induced proliferation. When GC were induced in mice with cytochrome c and myelin basic protein, the GC T cells were found to preferentially express V alpha 11 and V beta 8 TCR families, which are, respectively, the dominant TCR families in these two responses. Furthermore, GC T cells have proliferated upon exposure to the Ag that induced GC formation. Taken together, these results demonstrate that GC must recruit and retain Ag-specific T cells, thus implicating the GC as an in vivo site where Ag-specific T and B cells interact.

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. V. In vivo expression of individual antibody clones is dependent on Ig CH haplotypes and the categories of antigen

Antibodies (Ab) to the polysaccharide capsule of Haemophilus influenzae type b (Hib-PS) provide protection against Haemophilus influenzae type b disease in children, and Hib-PS vaccines with different immunologic properties are widely used clinically. The repertoire of human anti-Hib-PS Ab induced by these vaccines is relatively restricted and can be divided into two types by the structure of the light chain V region. Ab using A2-V kappa II gene product, which account for the majority of anti-Hib-PS Ab response in most patients, show little somatic mutations. In contrast, non-Ab using A2-V kappa II gene product use VL genes from the V kappa I, V kappa II, V kappa III, V kappa IV, and V lambda subgroups, are variably expressed among patients, and contain somatic mutations. To further study the expression of these two types of anti-Hib-PS Ab, we have produced KB13, a mAb specific for V kappa II subgroup, and used mAb specific for various other VL subgroups to develop immunoassays specific for anti-Hib-PS Ab of each VL subgroup. When Ig allotypes were studied for the effect on the Ab repertoire, A2-V kappa II (A2) Ab were found to be expressed less in patients expressing fb or zag CH haplotypes (p < 0.05). When the T cell-independent Hib-PS carbohydrate vaccine was compared to two T cell-dependent Hib-PS protein conjugate vaccines for their effect on Ab repertoire, Ab using V kappa III VL were found to be more often elicited with the conjugate vaccines than with the Hib-PS carbohydrate vaccine (p < 0.01). Thus, individual members of the anti-Hib-PS Ab repertoire differ not only in their V region structure but also in the control of their expression.

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. V. In vivo expression of individual antibody clones is dependent on Ig CH haplotypes and the categories of antigen

Antibodies (Ab) to the polysaccharide capsule of Haemophilus influenzae type b (Hib-PS) provide protection against Haemophilus influenzae type b disease in children, and Hib-PS vaccines with different immunologic properties are widely used clinically. The repertoire of human anti-Hib-PS Ab induced by these vaccines is relatively restricted and can be divided into two types by the structure of the light chain V region. Ab using A2-V kappa II gene product, which account for the majority of anti-Hib-PS Ab response in most patients, show little somatic mutations. In contrast, non-Ab using A2-V kappa II gene product use VL genes from the V kappa I, V kappa II, V kappa III, V kappa IV, and V lambda subgroups, are variably expressed among patients, and contain somatic mutations. To further study the expression of these two types of anti-Hib-PS Ab, we have produced KB13, a mAb specific for V kappa II subgroup, and used mAb specific for various other VL subgroups to develop immunoassays specific for anti-Hib-PS Ab of each VL subgroup. When Ig allotypes were studied for the effect on the Ab repertoire, A2-V kappa II (A2) Ab were found to be expressed less in patients expressing fb or zag CH haplotypes (p &lt; 0.05). When the T cell-independent Hib-PS carbohydrate vaccine was compared to two T cell-dependent Hib-PS protein conjugate vaccines for their effect on Ab repertoire, Ab using V kappa III VL were found to be more often elicited with the conjugate vaccines than with the Hib-PS carbohydrate vaccine (p &lt; 0.01). Thus, individual members of the anti-Hib-PS Ab repertoire differ not only in their V region structure but also in the control of their expression.

Endogenous antibodies that interfere with thyroxine fluorescence polarization assay but not with radioimmunoassay or EMIT

We have identified an individual whose thyroxine (T4) concentration was undetectable with Abbott's fluorescence polarization immunoassay (FPIA) but within the reference range by radioimmunoassay or EMIT (Syva). The patient's thyrotropin, triiodothyronine, and T-uptake values were within the normal range. The T4 concentration measured by FPIA increased to normal when the immunoglobulin fraction was selectively removed from the serum. When the patient's immunoglobulin fraction was added to normal serum, the T4 content of the normal serum measured by FPIA became falsely low. The patient's antibody interfered with the T4 FPIA by binding to the fluorescein-T4 conjugate. The T-uptake was less affected by the patient's serum because of the low affinity of the patient's antibody to fluorescein-T4 (K = 3.5 x 10(8) L/mol). The patient's immunoglobulin bound preferentially to fluorescein-T4, in comparison with binding to fluorescein or T4 alone. We conclude that the patient's immunoglobulin bound to an epitope unique to the fluorescein-conjugated T4.

Endogenous antibodies that interfere with thyroxine fluorescence polarization assay but not with radioimmunoassay or EMIT

We have identified an individual whose thyroxine (T4) concentration was undetectable with Abbott's fluorescence polarization immunoassay (FPIA) but within the reference range by radioimmunoassay or EMIT (Syva). The patient's thyrotropin, triiodothyronine, and T-uptake values were within the normal range. The T4 concentration measured by FPIA increased to normal when the immunoglobulin fraction was selectively removed from the serum. When the patient's immunoglobulin fraction was added to normal serum, the T4 content of the normal serum measured by FPIA became falsely low. The patient's antibody interfered with the T4 FPIA by binding to the fluorescein-T4 conjugate. The T-uptake was less affected by the patient's serum because of the low affinity of the patient's antibody to fluorescein-T4 (K = 3.5 x 10(8) L/mol). The patient's immunoglobulin bound preferentially to fluorescein-T4, in comparison with binding to fluorescein or T4 alone. We conclude that the patient's immunoglobulin bound to an epitope unique to the fluorescein-conjugated T4.

Cytokine expression by germinal center cells

Germinal centers (GC) primarily consist of B cells along with a small number of T cells (5 to 10%) and follicular dendritic cells (FDC) (< or = 1%). Although extensive Ag-driven B cell proliferation and maturation occurs in GC, very little is known about the role of cytokines in the development of GC B cells. Therefore, to identify cytokines present in the GC microenvironment that may influence B cell development, we systematically examined cytokine gene expression by GC cells. GC T cells (CD57+/CD4+), GC B cells (CD77+), and FDC (HJ2+) were isolated from human tonsils by cell sorting using a flow cytometer. Freshly isolated GC cells were examined for mRNA expression for IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, TNF-alpha, and IFN-gamma using reverse transcription polymerase chain reaction. Freshly isolated GC T cells consistently expressed IL-4 mRNA (11 of 12 tonsils), whereas CD57- Th cells (mostly non-GC Th cells) were often negative for IL-4 mRNA. When the other nine cytokine mRNA were studied, freshly isolated CD57+ Th cells occasionally expressed mRNA for IL-10, TNF-alpha, and IFN-gamma. CD57- Th cells were occasionally positive for IL-1 beta, IL-10, IFN-gamma, and TNF-alpha, and negative for IL-2 and IL-6. Freshly isolated GC B cells as well as FDC failed to express detectable quantities of mRNA for all 10 cytokines that were studied. Thus, IL-4 is the only cytokine out of 10 that is consistently expressed in GC and may be important for the development of B cells in GC. After stimulation of CD57+ Th cells with PWM, production of IL-4 mRNA was dramatically reduced, whereas CD57- Th cell production of IL-4 was greatly augmented. This finding indicates that GC T cells may differ from other Th cells in cytokine gene expression and that results of cytokine production obtained after in vitro stimulation do not always reflect in vivo results.

Cytokine expression by germinal center cells

Germinal centers (GC) primarily consist of B cells along with a small number of T cells (5 to 10%) and follicular dendritic cells (FDC) (&lt; or = 1%). Although extensive Ag-driven B cell proliferation and maturation occurs in GC, very little is known about the role of cytokines in the development of GC B cells. Therefore, to identify cytokines present in the GC microenvironment that may influence B cell development, we systematically examined cytokine gene expression by GC cells. GC T cells (CD57+/CD4+), GC B cells (CD77+), and FDC (HJ2+) were isolated from human tonsils by cell sorting using a flow cytometer. Freshly isolated GC cells were examined for mRNA expression for IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, TNF-alpha, and IFN-gamma using reverse transcription polymerase chain reaction. Freshly isolated GC T cells consistently expressed IL-4 mRNA (11 of 12 tonsils), whereas CD57- Th cells (mostly non-GC Th cells) were often negative for IL-4 mRNA. When the other nine cytokine mRNA were studied, freshly isolated CD57+ Th cells occasionally expressed mRNA for IL-10, TNF-alpha, and IFN-gamma. CD57- Th cells were occasionally positive for IL-1 beta, IL-10, IFN-gamma, and TNF-alpha, and negative for IL-2 and IL-6. Freshly isolated GC B cells as well as FDC failed to express detectable quantities of mRNA for all 10 cytokines that were studied. Thus, IL-4 is the only cytokine out of 10 that is consistently expressed in GC and may be important for the development of B cells in GC. After stimulation of CD57+ Th cells with PWM, production of IL-4 mRNA was dramatically reduced, whereas CD57- Th cell production of IL-4 was greatly augmented. This finding indicates that GC T cells may differ from other Th cells in cytokine gene expression and that results of cytokine production obtained after in vitro stimulation do not always reflect in vivo results.

Standardization of glycohemoglobin determinations in the clinical laboratory: three years of experience

Measurement of glycohemoglobin has been recommended for the long-term assessment of glycemic control in diabetic patients. Because different analytical methods measure different glycohemoglobin species, it has been difficult to compare results between laboratories. Here we report 3 years of experience with calibration of an affinity chromatography method for measuring total glycohemoglobin (GHb). Calibration was achieved by including in each assay three hemolysate calibrators for which values for HbA1c and GHb had been determined by repeated analyses by high-performance liquid chromatography (HPLC) and affinity chromatography, respectively. Calibration improved interassay precision (CV = 3.20-7.90% and < 5.0% before and after the introduction of calibration, respectively) and eliminated lot-to-lot variability. In 91 samples, HbA1c was estimated by the calibrated affinity chromatography assay and measured by an ion-exchange HPLC method. Estimated and HPLC-measured HbA1c showed no clinically significant differences during 36 months. The high degree of long-term precision, the disappearance of lot-to-lot variability, and the excellent comparability between analytical methods measuring different species of glycated hemoglobins demonstrate the advantages of calibration.

Standardization of Glycohemoglobin Determinations in the Clinical Laboratory: Three Years of Experience

Measurement of glycohemoglobin has been recommended for the long-term assessment of glycemic control in diabetic patients. Because different analytical methods measure different glycohemoglobin species, it has been difficult to compare results between laboratories. Here we report 3 years of experience with calibration of an affinity chromatography method for measuring total glycohemoglobin (GHb). Calibration was achieved by including in each assay three hemolysate calibrators for which values for HbA1c and GHb had been determined by repeated analyses by high-performance liquid chromatography (HPLC) and affinity chromatography, respectively. Calibration improved interassay precision (CV = 3.20-7.90% and &lt; 5.0% before and after the introduction of calibration, respectively) and eliminated lot-to-lot variability. In 91 samples, HbA1c was estimated by the calibrated affinity chromatography assay and measured by an ion-exchange HPLC method. Estimated and HPLC-measured HbA1c showed no clinically significant differences during 36 months. The high degree of long-term precision, the disappearance of lot-to-lot variability, and the excellent comparability between analytical methods measuring different species of glycated hemoglobins demonstrate the advantages of calibration.

The evolution of immune memory and germinal centers

Antibody responses in homoiothermic and poikilothermic vertebrates are significantly different in their heterogeneity and affinity range, and in the speed of the secondary response following repeated antigenic stimulation. This article presents the hypothesis that the evolutionary development of unique lymphoid structures, the germinal centers, in combination with the development of a distinct B-cell lineage, is a determining feature of these differences.

Characterization of the human IgG antibody VL repertoire to Haemophilus influenzae type b polysaccharide

The human antibody response to the capsular polysaccharide of Haemophilus influenzae type b (Hib) is a good model for examining human V region repertoires. While the VL repertoire of human antibodies to Hib polysaccharide is relatively simple and dominated by the product of a germline V kappa II gene named A2, at least five other VL genes can be expressed by some individuals. These include at least two V kappa I products and at least one V kappa III, one V kappa IV, and one V lambda product. The epitope recognized by a monoclonal anti-idiotype antibody is on the A2 V kappa II product.

Functional properties of human germinal center B cells

Germinal centers (GCs) are histologically defined areas where B cells undergo extensive proliferation and maturation, or die of apoptosis. GC B cells isolated from human tonsils can be phenotypically identified by expression of peanut agglutinin (PNA)-binding sites and can be further divided into subpopulations based on their expression of CD77. To assess the functional potential of GC B cells, we studied CD77+ PNA+ B cells isolated from tonsils by examining their differentiation status and their ability to proliferate in vitro to various cytokines and costimulants. We found that CD77+ GC B cells are less differentiated than CD77- GC B cells; GC B cells less frequently express cytoplasmic IgG and IgM, and spontaneously secrete less Ig compared to CD77- GC B cells. To identify conditions capable of inducing GC B cell proliferation, we examined IL-4, IL-2, IFN-gamma, low molecular weight BCGF (LMW-BCGF), and an MLR supernatant along with costimulants such as anti-IgM antibody, Staphylococcus aureus Cowan I (SAC), PMA, and pokeweed mitogen (PWM). While non-GC B cells proliferate strongly in response to these stimuli, GC B cells did not proliferate. However, CD77+ as well as CD77- GC B cells mounted a rapid and strong proliferative response upon stimulation with IL-4, but only in the presence of anti-CD40 antibody. Moreover, although nine additional cytokines were examined, only IL-4 was capable of supporting CD77+ GC B cell proliferation in the presence of anti-CD40 antibody. When cells were stimulated with IL-4 and anti-CD40 antibody, we also found that IFN-gamma consistently decreased the proliferative response of CD77+ GC B cells without affecting the response of non-GC B cells. Taken together, these data indicate that GC B cells have characteristic growth requirements and that IL-4 may be important for GC B cell growth in vivo.

The human antibody V region repertoire to the type B capsular polysaccharide of Haemophilus influenzae

The V region repertoire of the human antibody response to the type b capsular polysaccharide of Haemophilus influenzae (Hib-PS) is being defined at the molecular level using antibodies purified from serum of immunized adults. The VH of this response is restricted to the VHIII subgroup while the VL can be divided into two categories. The most common VL, expressed in > 90% of adults and usually constituting the majority of a subjects anti-Hib-PS antibody response, is restricted to the product of a single V kappa II gene known as A2 that probably lacks somatic mutations. The product of the A2 gene is invariably joined to one of several J kappa products by an inserted arginine at the V kappa-J kappa junction. In contrast to the restricted nature of the dominant VL clonotype, the second category of VL constitutes a heterogeneous group of at least seven different VL gene products that often contain somatic mutations and generally exhibit crossreactivity with a related polysaccharide from E. coli. Elucidation of anti-Hib-PS V regions at the molecular level will permit examination of structure-function relationships among these clinically important antibodies and should make the V region repertoire to Hib-PS a useful model for studying human V gene responses.

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. IV. The less frequently expressed VL are heterogeneous

We previously demonstrated that the human anti-Haemophilus influenzae type b polysaccharide (Hib-PS) VL repertoire is dominated by a product of the V kappa II gene, A2, and that V kappa II-A2 anti-Hib-PS antibodies have little or no somatic mutation in VL. To further study this VL repertoire, we studied non-A2 anti-Hib-PS antibodies that were identified either serologically or by amino-terminal amino acid sequence analysis. Of 15 non-A2 anti-Hib-PS antibodies from 12 vaccinated adults, we found four V lambda, five V kappa I, one non-A2 V kappa II, four V kappa III, and one V kappa IV antibodies. As expected, all but two of these subjects also produced V kappa II-A2 antibodies. Interestingly, one of these subjects lacks the A2 gene in the germ line. However, both subjects who did not produce detectable V kappa II antibody did produce normal amounts of total anti-Hib-PS antibody after vaccination. Candidate V kappa genes for the non-A2 antibodies were identified by comparison of up to 60 VL amino acid residues, including CDR1 and CDR2, with all sequenced V kappa genes. V kappa I antibodies appear to be products of three newly sequenced V kappa I genes, O8, O18, and L11, that are reported here. The O8 and O18 genes encode identical amino acid sequences. The non-A2 V kappa II antibody is a likely product of the A1 or A17 genes, the V kappa III antibodies are likely products of the A27 gene, and the V kappa IV antibody is a product of the single V kappa IV gene, B3. Unlike V kappa II-A2 antibodies, the V kappa I, V kappa III, and V kappa IV antibodies differed by one to five CDR residues from the germ line product of the candidate genes, suggesting the presence of somatic mutations. Thus, anti-Hib-PS antibodies can be divided into two types, the most frequently observed A2 antibodies with little or no somatic mutation and non-A2 antibodies that likely contain somatic mutations.

An idiotypic marker associated with a germ-line encoded kappa light chain variable region that predominates the vaccine-induced human antibody response to the Haemophilus influenzae b polysaccharide

Human antibodies specific for the Haemophilus influenzae b polysaccharide (Hib PS) frequently express a cross-reactive idiotype (CRI), and commonly utilize a VL region that is the product of the V kappa II gene A2. To examine further anti-Hib PS V region expression and to determine whether CRI expression is correlated with the V kappa IIA2 chain, we isolated a monoclonal antibody (MAb) reactive with an idiotypic determinant of anti-Hib PS antibodies. This MAb inhibited Hib PS binding but did not react with Ig isotypic determinants. The CRI recognized by this MAb, designated HibId-1, was associated with the Hib PS-combining site since the reactivity of the MAb with anti-Hib PS antibodies could be inhibited by Hib PS. HibId-1 was expressed by 17 of 17 clonally purified and sequence-defined anti-Hib PS antibodies having V kappa IIA2 L chains. In contrast, 0 of 10 anti-Hib PS antibodies having either V lambda, V kappa I, or V kappa III chains expressed HibId-1. Western blot analysis showed that the MAb anti-CRI reacted with isolated anti-Hib PS V kappa IIA2 L chains but not with H chains or other L chains, indicating that the HibId-1 determinant is localized to the V kappa IIA2 chain, and does not require pairing with H chain for expression. Anti-Hib PS antibodies bearing HibId-1 were present in at least 85% of subjects immunized with either free Hib PS or Hib PS coupled to diphtheria toxoid (Hib PS-DT), and comprised on the average 60% of the total vaccine-induced serum anti-Hib PS. HibId-1 expression was not related to age at vaccination inasmuch as infants, children, and adults had similar distributions of HibId-1-positive anti-Hib PS after vaccination with Hib PS-DT. HibId-1 was expressed at a lower frequency and comprised a smaller fraction of the total anti-Hib PS antibody in adult preimmunization sera as compared to post-Hib PS immunization sera, suggesting that immunization preferentially stimulates HibId-1-positive B cells. These data demonstrate that antibodies bearing HibId-1/V kappa IIA2 comprise a predominant component of the anti-Hib PS response induced by immunization, and that this pattern of VL expression is established early in ontogeny.

Clonal characterization of the human IgG antibody repertoire to Haemophilus influenzae type b polysaccharide. IV. The less frequently expressed VL are heterogeneous

We previously demonstrated that the human anti-Haemophilus influenzae type b polysaccharide (Hib-PS) VL repertoire is dominated by a product of the V kappa II gene, A2, and that V kappa II-A2 anti-Hib-PS antibodies have little or no somatic mutation in VL. To further study this VL repertoire, we studied non-A2 anti-Hib-PS antibodies that were identified either serologically or by amino-terminal amino acid sequence analysis. Of 15 non-A2 anti-Hib-PS antibodies from 12 vaccinated adults, we found four V lambda, five V kappa I, one non-A2 V kappa II, four V kappa III, and one V kappa IV antibodies. As expected, all but two of these subjects also produced V kappa II-A2 antibodies. Interestingly, one of these subjects lacks the A2 gene in the germ line. However, both subjects who did not produce detectable V kappa II antibody did produce normal amounts of total anti-Hib-PS antibody after vaccination. Candidate V kappa genes for the non-A2 antibodies were identified by comparison of up to 60 VL amino acid residues, including CDR1 and CDR2, with all sequenced V kappa genes. V kappa I antibodies appear to be products of three newly sequenced V kappa I genes, O8, O18, and L11, that are reported here. The O8 and O18 genes encode identical amino acid sequences. The non-A2 V kappa II antibody is a likely product of the A1 or A17 genes, the V kappa III antibodies are likely products of the A27 gene, and the V kappa IV antibody is a product of the single V kappa IV gene, B3. Unlike V kappa II-A2 antibodies, the V kappa I, V kappa III, and V kappa IV antibodies differed by one to five CDR residues from the germ line product of the candidate genes, suggesting the presence of somatic mutations. Thus, anti-Hib-PS antibodies can be divided into two types, the most frequently observed A2 antibodies with little or no somatic mutation and non-A2 antibodies that likely contain somatic mutations.

Subpopulations of B cells in germinal centers. III. HJ6, a monoclonal antibody, binds globoside and a subpopulation of germinal center B cells

To identify surface Ag uniquely expressed on human germinal center B cells, we produced a mouse mAb, HJ6. When tonsillar lymphocytes were examined, HJ6 did not label T cells and labeled only about half of PNA+ B cells that were HK23-. HJ6 did not label mononuclear cells from peripheral blood, splenocytes, and any of 29 cell lines including 23 B cell lines. This binding pattern of HJ6 was very similar to that of a mAb named 5B5. It was shown previously that 5B5 bound a glycolipid named CTH (CD77) and its Ag was expressed on HK23- PNA+ tonsillar lymphocytes and Burkitt's lymphoma cell lines. Despite the similarity, HJ6 differed from 5B5: HJ6 did not stain Burkitt's lymphoma cell lines and stained PNA+ tonsillar lymphocytes in the presence of a large concentration of galactose. When its binding to isolated glycolipids was studied, HJ6 was found to bind globoside and Forssman Ag and not to other glycolipids including CTH. When its binding to neutral glycolipids extracted from tonsillar lymphocytes was studied, HJ6 bound only globoside; Forssman Ag was not detected in tonsillar lymphocytes. Taken together, we conclude that globoside is a B cell Ag expressed on a subpopulation of germinal center B cells.