Association of placental transfer of anti-Haemophilus influenzae type b polysaccharide antibodies with their V regions

Immunization of mothers during pregnancy may be an effective means of providing protection to infants during the first months of life against many pathogens. Previous studies have identified factors that influence the transfer of immunoglobulin across the placenta, including the time of vaccination during pregnancy and isotypes of specific immunoglobulins. By studying antibodies to Haemophilus influenzae type b polysaccharide (Hib-PS) in 26 pairs of maternal-cord sera obtained from unimmunized healthy women and 22 pairs of maternal-cord sera from women immunized with one of three different Hib vaccines, we have found that the immunoglobulin transfer is also dependent on the V region of antibodies. Anti-Hib-PS derived from the V kappa II gene "A2" was transferred about ten times more efficiently to the fetus than other anti-Hib-PS antibodies (20% vs 1-2%). It was found that antibodies derived from the A2 V kappa gene are primarily IgG whereas other antibodies are preferentially associated with the IgM isotype. The potential association between the antibody V region with preferential placental transfer should be considered for future studies involving maternal immunization.

Neoaloesin A: a new C-glucofuranosyl chromone from Aloe barbadensis

The first C-glucofuranosyl compound, named as neoaloesin A, was isolated from the leaves of Aloe barbadensis. Its structure was determined to be 8-alpha-D-glucofuranosyl-7-hydroxy-5-methyl-2-(2-oxopropyl)-4 H-1-benzopyran-4-one on the basis of chemical and spectral evidence.

The repertoire of human antibodies to the carbohydrate capsule of Streptococcus pneumoniae 6B

Antibodies to Streptococcus pneumoniae 6B capsular polysaccharide (PS) induced with a 23-valent PS vaccine among 25 adults were examined. The magnitude of antibody responses among different subjects was highly correlated with the amount of anti-6B antibodies expressing IgG (r = 0.98) and lambda (r = 0.93) isotypes. Most individuals produced one or two dominant IgG antibody clones as identified by their isoelectric points. Two antibody clones with unique amino acid sequences could be readily purified, and the sequences of their light chains match those of A1/A17 V kappa and hslv2046 V lambda genes. Anti-6B antibodies isolated from different subjects used various VL genes and differed in their cross-reactivity with 6A PS. An isoelectric focusing study suggests that some IgG antibodies induced with 6B PS bind 6A PS with lower avidity.

High frequency plant regeneration via somatic embryogenesis in cell suspension cultures of coriander (Coriandrum sativum L.)

Hypocotyl segments and zygotic embryos of coriander formed embryogenic calli at frequencies of up to 75% when cultured on MS medium supplemented with 1 mgl(-1) 2,4-D. Calli were transferred to MS liquid medium with 1 mgl(-1) 2,4-D to initiate cell suspension cultures. Embryogenic cells became finely dispersible in the medium as the subculture proceeded. Cultures were transferred to a nitrogen compound enriched liquid MS medium containing 2% sucrose and 0.1 mgl(-1) 2,4-D, and cultured two weeks before plating on MS basal medium. Approximately 75% of cell aggregates (1 to two mm in diameter) underwent development into globular to cotyledonary somatic embryos after two weeks of plating. Most of the embryos were subsequently regenerated into plantlets. Regenerants were successfully transplanted to potting soil and grown to maturity in a phytotron.

Molecular characteristics of the N-terminal region of the quail follitropin receptor

We determined the primary structure of follitropin receptor (FSH-R) at its N-terminal extracellular domain, which is the key region of specific hormone binding in avian (quail) species. In this region, quail FSH-R showed about 70% homology with mammalian FSH-Rs at the level of predicted amino acid sequences. The leucine-rich repetitive motif which is conserved in all mammalian FSH-Rs was also detected in the quail FSH-R. However, some unique amino acid replacements were found at the positions of cystein residues and potential N-linked glycosylation sites. The sequence of the quail lutropin receptor (LH-R) previously defined by us showed a homology between FSH-R and LH-R of 47.4%. This value is close to those between mammalian FSH-Rs and LH-Rs, which in the corresponding region are human, 50.3%; rat, 50.9%.

Effects of unilateral cryptorchidism on the expression of gonadotropin receptor mRNA

Expression patterns of mRNAs of FSH and LH receptors were examined by Northern blot in adult rat testes after induction of unilateral cryptorchidism. At 4 weeks after the operation, signals of Northern blot were markedly increased in both receptor mRNAs in the abdominal testes as compared to those in the scrotal testes. In addition, there was a remarkable change in size pattern of LH receptor transcripts; the scrotal testes of cryptorchid rats and the intact testes of control rats expressed the transcripts of 7.0, 4.3, 2.5, and 1.8 kb, while the abdominal testes hardly expressed the transcript of 1.8 kb. This finding suggests that the expression of LH receptor mRNA is regulated locally within testis.

Chronic effect of hyperprolactinemia on blood glucose and lipid levels in mice

We studied the chronic effects of hyperprolactinemia, induced by ectopic pituitary grafting, on blood glucose and lipid levels in adult male mice. For one year after pituitary grafting, we measured the blood levels of prolactin, growth hormone (GH), insulin, glucose and free fatty acid (FFA) at various intervals. The graft caused consistent hyperprolactinemia without changes in the serum GH levels. Hypoglycemia developed at 1 and 3 months after grafting but was not accompanied by any changes of the serum insulin levels. Thereafter, the blood glucose and serum insulin levels began to increase in the pituitary-grafted (PG) mice, and at 12 months after the operation, both levels became significantly higher in PG mice than controls. The serum FFA levels and the weight of epididymal fat bodies were significantly lower in PG mice than controls from 3-12 months after the grafting. Thus, hyperprolactinemia leads to persistent hypolipidemia and biphasic changes in the blood glucose level.

Changes in citrate concentration in the mouse uterus with experimentally-induced adenomyosis

Components of the uterine fluid in mice with experimentally-induced adenomyosis and in controls were examined by proton nuclear magnetic resonance spectroscopy. One of the components was markedly different in mice with adenomyosis. As this component was estimated to be citrate by comparison with authentic samples (standard spectrum), its levels in uterine fluid, uterine tissue and blood were determined by enzymatic analysis. The fluid obtained from the uterus with adenomyosis showed significantly lower concentration of citrate than that from normal uterus. However, the uterine tissue concentration was significantly higher in the experimental mice with adenomyosis. There was no difference in the blood citrate level between the experimental and the control groups. Since adenomyosis was induced by chronic hyperprolactinemia, the change of citrate level in the uterus with this lesion might imply some effects of prolactin (PRL) on metabolism and/or secretion of citrate. However, in normal mice, no significant change was demonstrated in uterine citrate concentration after short-term experimental modulation of the circulating PRL level. Thus, it is unlikely that PRL can regulate directly citrate metabolism in the uterus, indicating some other cause for changes in citrate level accompanying the development of adenomyosis.

Redox agents as a link between hypoxia and the responses of ionic channels in rabbit pulmonary vascular smooth muscle

Ca(2+)-activated K+ currents (IK(Ca)) and voltage-dependent Ca(2+)-insensitive K+ currents (IK(V)) were recorded using the patch clamp technique to study the pulmonary (PASMC) and ear arterial smooth muscle cells (EASMC) of the rabbit and the possible regulatory mechanisms related to hypoxia. When a hypoxic solution (1 mM Na2S2O4, gassed with 100% N2) was superfused, the activity of Ca(2+)-activated K+ channels (KCa channels) recorded at a pipette potential of -70 mV in cell-attached mode was decreased to 49 +/- 7% in PASMC, whereas EASMC KCa channels did not respond to hypoxia. In inside-out patches (bathed symmetrically in 150 mM KCl), reducing agents such as dithiothreitol (DTT; 5 mM), reduced glutathione (GSH; 5 mM) and NADH (2 mM) decreased KCa channel activity in PASMC, but they did not affect the EASMC KCa channel. However, oxidizing agents such as 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB; 1 mM), oxidized GSH (GSSG; 5 mM) and NAD (2 mM) increased KCa channel activity in both PASMC and EASMC. In the whole-cell configuration, using a pipette solution containing a high concentration of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA; 10 mM), PASMC IK(V) were activated by depolarizing step pulses to voltages more positive than -30 mV (holding potential, -80 mV). IK(V) was increased by application of a membrane-permeable oxidizing agent, 2,2'-dithio-bis(5-nitropyridine) (DTBNP; 200 microM), whereas it was decreased by application of DTT (5 mM). From these results, it could be suggested that hypoxic pulmonary vasoconstriction is attributable, at least in part, to a change of cellular redox state, which decreases outward K+ currents. This hypothesis is further supported by the observation that the basal redox state of EASMC KCa channels is more reduced than that of PASMC KCa channels. The distinct responses to hypoxia of pulmonary and systemic arterial smooth muscle could be explained by this difference.

Modification of pancreatic digestive function by pituitary grafting in mice

The effect of prolactin on the digestive potency of the acinar pancreas was examined in pituitary-grafted hyperprolactinemic mice, because our previous experiment showed that a marked proliferation of pancreatic acinar cells was induced by pituitary grafting in mice. To know whether the digestive function is modified, the tissue contents of pancreatic digestive enzymes, such as chymotrypsin, lipase alpha-amylase and ribonuclease, were measured in the hyperprolactinemic mice. Pituitary grafting significantly increased the contents of chymotrypsin and lipase in the pancreas on day 12 after the operation without affecting intake of food, when compared to those in the sham-operated controls. On day 30, however, the differences between pituitary-grafted and control mice were no more discernible. Thus, the digestive enzyme activities are easily modified soon after the increase of circulating prolactin level. This effect of prolactin on the function of the pancreas may be responsible for "homeorhetic" control of nutrients during lactation. In another set of experiments in adrenalectomized-castrated or castrated mice, pituitary grafting induced an increase in the weight of the pancreas. In addition, adrenalectomy in combination with castration did not alter the pancreatic contents of chymotrypsin and lipase but decreased the amylase content. These results taken together seem to indicate that the effect of prolactin on the exocrine pancreas is not mediated by gonadal and adrenal steroid hormones.

Functional capacities of clonal antibodies to Haemophilus influenzae type b polysaccharide

Haemophilus influenzae type b (Hib) is an important pathogen for young children, and children can be protected with antibodies (Abs) to Hib polysaccharide (PS) capsule, a linear polymer of ribosyl ribitol phosphate. The structure of anti-Hib-PS Abs has been well characterized at the molecular level; about two-thirds of anti-Hib-PS Abs use a V kappa gene named A2, and the remaining anti-Hib-PS Abs use one of many other VL genes. In order to understand the structural basis for the variability in the function of these Abs, we prepared 18 clonally pure Abs from adults and studied their affinity, avidity, bactericidal potency in vitro, and ability to reduce bacteremia in newborn rats. Affinities and avidities were determined as the inverse of the concentrations of short (3 repeating units) and long (20 repeating units) ligands which could bind 50% of anti-Hib-PS Ab in solution, respectively. No significant correlations between the protection of newborn rats and affinity (r = 0.02) or avidity (r = 0.16) were observed. The amount of Ab required to kill 50% of bacteria in vitro decreased with avidity (r = -0.32), as expected. However, Abs with high affinity were unexpectedly found to have less bactericidal activity (r = 0.38). This suggests that avidity may be a better predictor of Ab function than affinity. Affinity and avidity results were negatively correlated (r = 0.76, P = 0.0022), and Abs that had A2 V kappa gene products had higher avidity (P < 0.05) and lower affinity (P = 0.06) than Abs that had other VL genes. A possible explanation of these observations is that the epitope for Abs with the A2 gene is within the Hib-PS chain itself, whereas the epitope for Abs with a non-A2 gene is the terminus of Hib-PS.

Different modulation of Ca-activated K channels by the intracellular redox potential in pulmonary and ear arterial smooth muscle cells of the rabbit

We investigated the electrical responses of Ca-activated K (KCa) currents induced by hypoxia and reduction or oxidation of the channel protein in pulmonary (PASMC) and ear (EASMC) arterial smooth muscle cells using the patch-clamp technique. In cell-attached patches, in the presence of a high K solution (containing 0.316 microM Ca2+), the activity of KCa channels from PASMC was decreased (by 49 +/- 7% compared to control, pipette potential = -70 mV) by changing to a hypoxic solution (1 mM Na2S2O4, aeration with 100% N2 gas). EASMC channels did not respond to hypoxia. In order to investigate the possible mechanisms involved, using inside-out patches bathed symmetrically in 150 mM KCl, we applied redox couples to the intracellular side. Reducing agents, such as dithiothreitol (DDT, 5 mM), reduced glutathione, (GSH, 5 mM), and nicotinamide adenine dinucleotide reduced (NADH, 2 mM) decreased PASMC, but not EASMC, KCa channel activity. However, oxidizing agents such as 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB, 1 mM), oxidized glutathione (GSSG, 5 mM) and NAD (2 mM) increased KCa channel activity in both PASMC and EASMC. The increased activity due to oxidizing agents was restored by applying reducing agents. From these results, we could suggest that the basal redox state of the EASMC KCa channel is more reduced than that of the PASMC channel, since the response of KCa channels of the EASMC to intracellular reducing agents differs from that of the PASMC. This difference may be related to the different responses of PASMC and EASMC KCa channels to hypoxia.

Characterization of gonadotropin-releasing hormone (GnRH)-immunoreactive protein in the rat pineal gland

The aim of the present study was to characterize GnRH-like substance(s) in the rat pineal gland using a monoclonal antibody, LRH13, as a probe. The epitope of LRH13 is between 2nd and 5th amino acid residues of the mammalian GnRH, and its immunological characters were previously defined by us. LRH13 could show strong immunological signal on the rat pineal gland. Immunoblot after SDS-PAGE of the pineal gland preparations showed a LRH13 immunoreactive band with apparent mol wt 52 kilo-Dalton (kD), which is much bigger than that of hypothalamic GnRH precursor (10 kD). The 52 kD protein, however, was detected from insoluble fraction of the pineal homogenate and liberated from the fraction by Triton X-100 (2%) treatment. On the other hand, NaCl (140 mM and 500 mM) or EDTA (10 mM) treatment failed to liberate. Two-dimensional gel electrophoresis showed that the 52 kD protein is a mixture of two proteins with different isoelectric points (pI approximately 6.8 and 7.0). Both proteins showed identical patterns of peptide mapping by V8 protease digestion, and they might be originated from the same peptide. These results suggest that the rat pineal GnRH-immunoreactive substance has a unique property as a membrane associate protein.

The difference in autofluorescence features of lipofuscin between brain and adrenal

Lipofuscin is the autofluorescent material, which accumulates with aging in the cells of various tissues. However, its autofluorescence characteristics are different among tissues. In the present study, the autofluorescence features of lipofuscin in the brain and adrenal were compared. In 18-21-month-old rats, the brain lipofuscin was granular and its autofluorescence was bright whitish-yellow to bright orange. On the contrary, the adrenal lipofuscin was not demarkated as granules, and its autofluorescence was subdued orange. The emission maximum of the bright whitish-yellow brain lipofuscin was 540 nm to 570 nm and that of the adrenal lipofuscin was 640 nm to 660 nm, when excited at 330 nm to 380 nm. When the spectra were drawn after correcting the wavelength-dependent bias of microspectrofluorometer, the autofluorescence spectra were consistent with microscopically observable tint. To conclude, the present results showed that the autofluorescence features of the bright whitish-yellow brain lipofuscin and the adrenal lipofuscin were quite different.

In situ detection of gonadotropin-releasing hormone (GnRH) receptor mRNA expression in the rat ovarian follicles

To clarify the target cells of GnRH in the ovary, in vivo expression of ovarian GnRH receptor mRNA was examined histologically by in situ hybridization in immature rats treated with PMSG only or in combination with hCG. Strong hybridization signals were observed in the granulosa cells of atretic follicles. However, no significant signals were found in the granulosa cells of healthy small, preantral, or early antral follicles. Healthy Graafian and preovulatory follicles also showed intense signals in their mural granulosa cells, but no signals were detected in the cumulus oophorus cells. Corpora lutea showed only weak signals, but luteinizing follicles probably after atresia exhibited signals of moderate intensity in their luteinized and remaining granulosa cells. No signals were detected in the theca cells and oocytes in all the follicles. Interstitial cells sometimes exhibited hybridization signals of moderate intensity, when the cells were eosinophilic. Pretreatment with different combinations of gonadotropins yielded different ovarian histology, but this had no influence on the localization of hybridization signals. These results, showing that the authentic GnRH receptor mRNA was expressed in a certain cell population in the rat ovary, suggest that the receptor is involved in the control of various ovarian functions including follicular development, atresia, ovulation, and luteinization after ovulation and follicular atresia.

Blood pressure measurement in children: a brief review

Blood pressure measurement in children is difficult and many inaccuracies are seen because of the method of measurement of the blood pressure cuff and the choice of apparatus with which to measure the blood pressure. This article will briefly review the ways in which blood pressures are measured in children and the accuracy of these different measures. Perioperative nurses should be acutely aware of the confusion in literature concerning blood pressure measurement in children. It is hoped that this discussion will help the perioperative nurse to choose the appropriate size cuff and the most accurate method of measurement.

Antibacterial phenylpropanoid glycosides from Paulownia tomentosa Steud

The butanol extract of Paulownia tomentosa stem showed antibacterial activity against Staphylococcus aureus (SG511, 285 and 503), Streptococcus pyogenes (A308 and A77) and Streptococcus faecium MD8b etc. The most active compound of the extract was identified to be campneoside I, which had a minimal inhibitory concentration (MIC) of 150 micrograms/ml against Streptococcus and Staphylococcus species. From such antibacterial activity, the methoxy group of campneoside I was postulated to be the essential element for the antibacterial activity.

Immunohistochemical double-labeling study of gonadotropin-releasing hormone (GnRH)-immunoreactive cells and oxytocin-immunoreactive cells in the preoptic area of the dwarf gourami, Colisa lalia

The distribution of gonadotropin-releasing hormone (GnRH)-immunoreactive (ir) cells in the preoptic area (POA) of the dwarf gourami, Colisa lalia, was immunohistochemically studied. These neurons form cell columns on both sides of the common ventricle, and their axons project to the pituitary gland by forming distinct bundles. Also examined was the distribution of isotocin (IST) cells in the POA by using an anti-oxytocin (OXT) serum which has been proven to crossreact with IST. These two kinds of immunoreactive cells were distributed quite similarly in the POA. However, by using an immunofluorescence double-labeling method on thinner sections we found that a population of small IST cells in the ventral POA were also immunoreactive to GnRH, but that large IST cells in the dorsal POA were not immunoreactive to GnRH, and small GnRH-ir cells in the most ventral POA were not immunoreactive to the OXT antiserum. In the pituitary gland, GnRH-ir fibers were found in both the neurohypophysis and proximal pars distalis, but IST fibers were found only in the neurohypophysis.

Characterization of cDNA-encoding N-terminal region of the quail lutropin receptor

For understanding the evolutionary relationships between gonadotropins [GTHs: lutropin (LH) and follitropin (FSH)] and their receptors, we attempted to characterize the extracellular domain of the receptors, which is thought to be a key region of hormone binding, in nonmammalian species, and to compare the information to that of the known mammalian data. For this purpose, we designed two sets of sense and antisense oligonucleotides as polymerase chain reaction (PCR) primers, referring to the known mammalian GTH receptors, such as LH receptors of human, pig, and rat, and FSH receptors of human and rat. All possible combinations of the primers showed the successful amplification of cDNA of LH receptor without contamination of FSH receptor cDNA from rat testicular RNA samples. With these primers, reverse transcription (RT)-PCR was applied to the gonads of nonmammalian species (quail, snake, tortoise, newt, and bullfrog). Only the quail, however, showed the specific amplification when only one set of primers was used. Thus, the PCR product of the quail was used as a probe for Northern blot and in situ hybridization. By Northern blot analysis, a single size of mRNA (3 kb) was identified from quail testicular poly A+ RNA. The distribution of mRNA visualized by in situ hybridization was limited only on Leydig cells of quail testis. These results suggest that a part of the quail LH receptor cDNA was amplified by RT-PCR. The nucleotide and predicted peptide sequences of this amplified cDNA were compared with those of mammalian receptors. The size of characterized cDNA sequence was 519 bp, which is completely identical with those of mammalian LH receptors. The homology of both cDNA and predicted peptide was about 70% of those of mammalian LH receptors (intramammalian, about 80%). In spite of the relatively low homology, the positions of cystein residues and potential N-linked glycosylation sites in the peptide were completely conserved in all species compared (human, pig, rat, and quail). The conserved portions indicate their importance for the molecular conformation and specific ligand binding activity of LH receptors.

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.

Effects of gonadotropin-releasing hormone (GnRH) on the cytodifferentiation of gonadotropes in rat adenohypophysial primordia in organ culture

The effects of gonadotropin-releasing hormone (GnRH) on the development of gonadotropes were investigated by the use of organ culture and by means of immunocytochemistry and radioimmunoassay. Pituitary primordia from rat fetuses were cultured in a medium with or without 10(-9) M GnRH during the first 24 h of culture. The ratio of the number of immunoreactive LH cells to the total number of cells in the explants derived from 13.5-day fetuses was increased by the GnRH treatment after 6 or 8 days of culture, while the total number of cells was not altered. LH released into the medium and LH content of explants were not affected by the GnRH treatment. Subsequent treatment with 10(-9) M GnRH for 4 h after 7 days of culture resulted in a marked release of LH, accompanying a significant decline in LH content, in both explants exposed or unexposed to the first GnRH treatment. However, the former explants contained a lower amount of LH than the latter explants. The present results indicate that pituitary primordia at 13.5 days of gestation are capable to respond to GnRH, and that GnRH is effective in stimulating the responsiveness of gonadotropes to GnRH during early pituitary cytodifferentiation.

Enhanced cell proliferation by hyperprolactinemia in both exocrine and endocrine pancreas in mice

Effects of hyperprolactinemia induced by ectopic anterior pituitary grafting on the pancreas were studied in male SHN mice. After pituitary grafting, the weight of pancreas rapidly increased. A similar increase in pancreatic weight was observed during lactation, a condition associated with elevated prolactin levels. Results of DNA and protein assays revealed that the increase in pancreatic weight in both pituitary-grafted and lactating mice was mainly due to the increase in the cell number, because the total DNA content per pancreas was greater in these mice than the controls. An increase in fluid volume or hypertrophy of cells also contributes to the weight increase; in contrast, the DNA and protein contents per unit tissue weight decrease. The rate of DNA synthesis determined by 5-bromo-2'-deoxyuridine labeling was higher both in acinar cells and islet B cells in pituitary-grafted mice than in the controls. Thus, hyperprolactinemia stimulates cell proliferation in exocrine pancreas as well as endocrine islets. The effect of prolactin seems to be indirect on acinar cells, because only B cells showed prolactin immunoreactivity in the mouse pancreas. In addition, insulin might not be a mediator of the prolactin effect on acinar cells, because the serum insulin level in pituitary-grafted mice failed to show any change.

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.