Primary murine immunoglobulin M responses to certain pneumococcal capsular polysaccharides consist primarily of anti-pneumococcal cell wall carbohydrate antibodies.

The antibody induced in mice immunized with a vaccine preparation of type 6 (Danish type 6A) pneumococcal capsular polysaccharide (S6) reacted with several chemically disparate pneumococcal capsular polysaccharides. Equivalent numbers of plaque-forming cells were observed when sheep erythrocytes coated with either S6, type 19 pneumococcal capsular polysaccharide (S19), or the pneumococcal cell wall carbohydrate (PnC) were used to detect the response to S6 or to S19. The addition of exogenous PnC to the plaquing mixtures of spleen cells from S6-, S19-, or PnC-immunized mice inhibited the appearance of most (greater than or equal to 85%) of the plaque-forming cells. Furthermore, the addition of monoclonal antibody specific for the dominant (TEPC 15) idiotype of anti-phosphorylcholine (a component of PnC) antibodies also inhibited the appearance of most of the plaque-forming cells. A suppressed S19 response was induced by priming mice with a low dose of S19 or PnC 3 days before immunization with an optimal dose of S19 (low-dose paralysis). These results demonstrated that most, if not all, of the antibody stimulated by these preparations of S6 and S19 was actually induced by and was specific for PnC.     

Antibodies against pneumococcal C-polysaccharide are not protective

The ability of antibodies against C-polysaccharide (C-Ps) to protect against experimental pneumococcal infection was examined in a mouse model. No protection against types 6A and 14 pneumococcal infection could be demonstrated neither with mouse monoclonal antibodies against C-Ps, specific for phosphorylcholine (PC) or for C-Ps backbone, nor for polyclonal rabbit immunsera against C-Ps. The monoclonal antibody with PC-specificity was protective against infection with type 27 pneumococcus, that has PC as part of its capsular polysaccharide. Type-specific mono- and polyclonal antibodies were highly protective against infection with the homologous type. We conclude that no species-specific protection can be achieved against intraperitoneal Streptococcus pneumoniae infection with optimally capsulated bacteria in outbred mice by passive immunization with antibodies to C-Ps.     

Interaction of the C-polysaccharide ofStreptococcus pneumoniaewith the receptor asialo-GM1

C-polysaccharide (PnC) is the major surface component of pneumococci containing phosphoryl choline residues. In order to investigate the possibility that PnC can bind to glycolipid receptors present on epithelial cells we extracted carbohydrate material from a nonencapsulated strain of pneumococci. The components of the extract were separated by gel permeation chromatography. An ELISA was used for detection of fractions binding to the pneumococcal glycolipid receptor asialo-GM1. These fractions were pooled and analysed by nuclear magnetic resonance spectroscopy (NMR). The¹H NMR spectrum showed good agreement with a reference spectrum of pure PnC showing that this substance was the major component. Binding of the purified PnC to asialo-GM1 was unaffected by protease K treatment. Immunoblots of the purified PnC after separation by SDS-PAGE resulted in a characteristic banding pattern. PnC could be released from pneumococci by heat treatment of whole bacteria in buffer as shown by reaction with a monoclonal antibody specific for the phosphoryl choline determinant. After separation by SDS-PAGE of the components of the heat extract, immunoblots showed the presence of bands characteristic for PnC. Eluates from the characteristic bands in the gel were shown to contain material binding to asialo-GM1. This binding was not reduced upon treatment with protease K. Pneumococci deprived of choline by cultivation in a medium containing ethanolamine as the only amino alcohol source did not bind to asialo-GM1, indicating that the phosphoryl choline residue of PnC is essential for the interaction between PnC and the glycolipid receptor. These data provide evidence that PnC containing an intact phosphoryl choline residue is a ligand responsible for binding of pneumococci to the receptor asialo-GM1.     

Type 6 and 19 pneumococcal polysaccharides coupled to erythrocytes elicit pneumococcal cell wall-specific primary IgM responses and capsular polysaccharide-specific secondary IgG responses

Previous results have shown that the primary murine antibody responses to vaccine preparations of type 6 (S6; Danish type 6A) or type 19 (S19; Danish type 19F) pneumococcal capsular polysaccharides consist entirely of IgM antipneumococcal cell wall carbohydrate (PnC)-specific antibodies. No capsular polysaccharide-specific IgM antibodies were detectable by plaque-forming cell or enzyme-linked immunosorbent assay techniques. In this report, antibodies specific for S6 and S19 capsular polysaccharides were induced in secondary responses to chicken erythrocyte (CRBC) conjugates of S6 and S19. Essentially all detectable IgG produced in the secondary response was capsular polysaccharide specific and included all subclasses of IgG. In contrast, all detectable IgM produced in the primary response to S6-CRBC and S19-CRBC, and the IgM produced in the secondary response to S6-CRBC was not capsular polysaccharide specific since it reacted with PnC. Thus, there is a major change in the specificity of the primary IgM response compared to the secondary IgG response of mice immunized with S6-CRBC or S19-CRBC. Injection of PnC or any PnC-containing polysaccharide prior to immunization with S6-CRBC or S19-CRBC resulted in suppression of the primary IgM response. In contrast, only the capsular polysaccharide used in the immunizing polysaccharide-erythrocyte conjugate suppressed induction of the capsular polysaccharide-specific secondary IgG response. These results suggest that S6 and S19 capsular polysaccharide-specific IgG-producing memory B cells derive from capsular polysaccharide-specific precursors which do not produce detectable antibody after primary immunization.     

Humoral responses to oxidized low-density lipoprotein and related bacterial antigens after pneumococcal vaccine

Antibodies to oxidized low-density lipoprotein (oxLDL) may modulate the development of atherosclerosis. Antibodies to oxLDL may also react with cell wall polysaccharides (CWPS) of Streptococcus pneumoniae because both antigens share a common phosphorylcholine moiety. In hypercholesteremic mice, immunization with pneumococcal organisms elicited antibodies to oxLDL and protection against atherosclerosis. In humans, we determined whether the widely used adult pneumococcal polysaccharide vaccine augmented antibodies to oxLDL, CWPS, and phosphorylcholine, providing the potential to retard atherogenesis. Before and 4 weeks after pneumococcal vaccination of 23 healthy adults (11 smokers and 12 matched nonsmokers), we characterized IgG, IgM, and IgA to pneumococcal capsular polysaccharides, CWPS, and phosphorylcholine, IgG and IgM to oxLDL, and fasting serum lipids. The pneumococcal vaccine elicited significant increases in each antibody class to surface capsular polysaccharides. In contrast, only IgG to CWPS increased modestly and only among smokers. Moreover, antibodies to neither phosphorylcholine nor oxLDL increased consistently in either group. The pneumococcal polysaccharide vaccine effectively elicits antibodies to the bacterial capsule. The vaccine had no effect on serum lipids. The vaccine did not augment antibodies to CWPS, to its component phosphorylcholine, or to oxLDL, which are antibodies that have been proposed to modify the uptake of oxLDL by macrophages and the pathogenesis of atherosclerosis.     

Enzyme immunoassay for detection of immunoglobulin G (IgG), IgM, and IgA antibodies against type 6B pneumococcal capsular polysaccharide and cell wall C polysaccharide in chinchilla serum.

Conjugation of the capsular polysaccharides of Streptococcus pneumoniae to protein carriers has introduced a new generation of pneumococcal vaccines which may be efficacious in preventing pneumococcal otitis media during infancy. The chinchilla model has been used extensively for studying the pathogenesis of pneumococcal otitis media and for testing the efficacy of early pneumococcal capsular polysaccharide (PCP) vaccines, but immunologic studies in the chinchilla have been limited by the lack of antibodies against specific immunoglobulin isotypes. By using affinity-purified rabbit immunoglobulin G (IgG) anti-chinchilla IgG, IgM, and IgA, we developed a sensitive enzyme immunoassay that is highly specific for IgG, IgM, and IgA antibodies against type 6B PCP (anti-6B) and against C polysaccharide in chinchilla serum. Antibody titers increased in serum from five chinchillas immunized with a type 6B outer membrane protein complex vaccine. Increases of anti-6B IgG and IgM antibody titers were more striking than increases of anti-6B IgA or anti-C polysaccharide IgG, IgM, or IgA titers were.     

Diagnosis of invasive pneumococcal infection by serotype-specific urinary antigen detection

Widespread use of conjugate pneumococcal polysaccharide-protein vaccines may alter the spectrum of pneumococci producing invasive disease. Novel sensitive diagnostic methods would be valuable for monitoring the epidemiology of pneumococcal disease within populations and vaccine recipients. Ideally, these methods should allow determination of the serotype of the infecting clone. Serotype-specific enzyme-linked immunosorbent assays (ELISA) for 13 capsular polysaccharides (types 1, 3, 4, 5, 6A, 6B, 7A, 9 V, 14, 18C, 19 A, 19F, and 23 F) were developed. Experiments with pure capsular polysaccharide demonstrated that the assays were sensitive (0.01 to 1.0 ng/ml) and specific. These assays were used to detect capsular polysaccharide in urine from 263 adult patients with proven (blood culture-positive) invasive pneumococcal disease and pneumonia of unknown etiology and from patients with positive blood cultures yielding bacteria other than pneumococci (control group). Among 76 patients with invasive pneumococcal disease from whom blood culture isolates had been serotyped, 62 (82%) had infections with pneumococci of serotypes represented in the ELISA panel. Capsular antigen matching the serotype of the blood culture isolate was detected in the urine of 52 of these patients, giving a sensitivity of 83.9% for the target serotypes. The tests were significantly more sensitive for urine from patients with pneumococcal pneumonia (89.8%) than for urine from patients with non-pneumonic invasive infection (61.5%; P<0.05). Data from the control group indicated a specificity of 98.8%. These assays should prove valuable in epidemiological investigation of invasive pneumococcal infection in adults, particularly if combined with a sensitive C-polysaccharide detection assay to screen for positive samples.     

A peptide mimotope of type 8 pneumococcal capsular polysaccharide induces a protective immune response in mice

Increasing antibiotic resistance and a rising patient population at risk for infection due to impaired immunity underscore the importance of vaccination against pneumococci. However, available capsular polysaccharide vaccines are often poorly immunogenic in patients at risk for pneumococcal disease. The goal of this study was to explore the potential of peptide mimotopes to function as alternative vaccine antigens to elicit a type-specific antibody response to pneumococci. We used a human monoclonal immunoglobulin A (IgA) antibody (NAD) to type 8 Streptococcus pneumoniae capsular polysaccharide (type 8 PS) to screen a phage display library, and the phage PUB1 displaying the peptide FHLPYNHNWFAL was selected after three rounds of biopanning. Inhibition studies with phage-displayed peptide or the peptide PUB1 and type 8 PS showed that PUB1 is a mimetic of type 8 PS. PUB1 conjugated to tetanus toxoid (PUB1-TT) induced a type 8 PS-specific antibody response in BALB/c mice, further defining it as a mimotope of type 8 PS. The administration of immune sera obtained from PUB1-TT-immunized mice earlier (days 14 and 21) and later (days 87 and 100) after primary and reimmunization resulted in a highly significant prolongation of the survival of naive mice after pneumococcal challenge compared to controls. The survival of PUB1-TT-immunized mice was also prolonged after pneumococcal challenge nearly 4 months after primary immunization. The efficacy of PUB1-TT-induced immune sera provides proof of principle that a mimotope-induced antibody response can protect against pneumococci and suggests that peptide mimotopes selected by type-specific human antibodies could hold promise as immunogens for pneumococci.     

Intranasal Immunization with Heat-Inactivated Streptococcus pneumoniae Protects Mice against Systemic Pneumococcal Infection

In order to study the mucosal and serum antibody response to polysaccharide-encapsulated bacteria in mice, a preparation of heat-inactivated Streptococcus pneumoniae type 4 was administered, with and without cholera toxin, at various mucosal sites. It appeared that intranasal immunization of nonanesthesized animals was superior to either oral, gastric, or colonic-rectal antigen delivery with regard to the induction of serum immunoglobulin G (IgG) and IgA, as well as saliva IgA antibodies specific for pneumococci. The marked IgA antibody response in feces after intranasal, but not after oral or gastric, immunization is suggestive of a cellular link between the nasal induction site and the distant mucosal effector sites. Intranasal immunization also induced antibodies in serum and in mucosal secretions against type-specific capsular polysaccharide. IgA and IgG antibody levels in pulmonary lavage fluids correlated well with saliva IgA and serum IgG antibodies, respectively. Antibody determinations in pulmonary secretions may therefore be redundant in some cases, and the number of experimental animals may be reduced accordingly. After intraperitoneal challenge with type 4 pneumococci, mice immunized intranasally were protected against both systemic infection and death, even without the use of cholera toxin as a mucosal adjuvant. Thus, an efficient intranasal vaccine against invasive pneumococcal disease may be based on a very simple formulation with whole killed pneumococci.     

Covalent linkage between the capsular polysaccharide and the cell wall peptidoglycan of Streptococcus pneumoniae revealed by immunochemical methods

The attachment of capsular polysaccharide to Streptococcus pneumoniae was examined using monoclonal and polyclonal antibodies. Among the strains examined, the capsular polysaccharide of types 2, 4, 6A, 6B, 7F, 8, 14, 19F and 23F was bound to the pneumococci whereas that of a type 3 strain was not. Sequential treatment with 2% SDS at 100 degrees C, pronase, and EDTA did not dissociate the capsular polysaccharide from the pneumococci. Treatment of the cells with mutanolysin, a muramidase that degrades the cell wall peptidoglycan of pneumococci and other streptococci, released both the capsular and the cell wall C-polysaccharide (C-Ps). Type 6A capsular polysaccharide released from cell walls by mutanolysin treatment, was fractionated by high performance liquid chromatography and examined by immunoelectrophoresis. It was found to be bound to both the C-Ps and the peptidoglycan. The bond between the capsular polysaccharide and the peptidoglycan has not yet been identified but is probably covalent, as the two components could not be dissociated after boiling in SDS. Based on our studies with type 6A, we propose that capsular polysaccharide and C-Ps of the pneumococcus are linked to the peptidoglycan at different sites and, thereby, indirectly to each other. Studies in mice showed that the peptidoglycan enhanced the serum antibody response to C-Ps but not to type 6A polysaccharide.     

Peptide mimics of two pneumococcal capsular polysaccharide serotypes (6B and 9V) protect mice from a lethal challenge with Streptococcus pneumoniae

Anti‐polysaccharide immunity is a key facet of protection against several bacterial pathogens. Problems exist with current polysaccharide vaccines and alternative strategies that deliver a protective response are needed. We have identified immunological peptide mimics of type 6B and 9V pneumococcal capsular polysaccharides that could be used as vaccine antigens. Peptides mimicking antigenic properties of serotype 6B capsular polysaccharide were obtained from a phage‐displayed peptide library expressing dodecameric peptides, using a human monoclonal antibody (Db3G9). A murine monoclonal antibody (206, F‐5) against the serotype 9V capsular polysaccharide identified three peptide mimotopes from the dodecameric peptide library and one from a random pentadecameric peptide library. In ELISA, binding of 206, F‐5 and Db3G9 to phage displaying the selected mimotopes was significantly inhibited by type‐specific pneumococcal polysaccharide. Peptides were conjugated to keyhole limpet haemocyanin and were used to immunise mice. Two peptides, MP13 and MP7, induced specific anti‐6B and 9V polysaccharide antibodies, respectively. Mice immunised with MP7‐keyhole limpet hemocyanin or MP13‐keyhole limpet hemocyanin conjugate were significantly and specifically protected against a lethal challenge with pneumococci of the appropriate serotype. This study provides strong in vivo evidence that peptide mimics are alternatives to polysaccharide vaccines.     

Monoclonal phosphorylcholine antibody binds to beta-lipoprotein from different animal species.

Previously published observations have demonstrated that murine antibody with specificity for phosphorylcholine (PC) binds to a variety of PC-containing polysaccharides and to human beta-lipoprotein. In this investigation it was found that monoclonal anti-PC antibody binds not only to human beta-lipoprotein, but also to beta-lipoprotein from the serum of all vertebrate species examined. beta-Lipoprotein from mouse reacted with autologous antibody; therefore, this antibody must be an autoantibody. This raises the question whether PC antibodies may exert unwanted effects after having been passively transferred or induced by PC-containing antigens, e.g., C-polysaccharide from pneumococci.     

The influence of genetic factors on the immune response as judged by pneumococcal vaccination of mono- and dizygotic Caucasian twins.

Eighty-four mono- and dizygotic Caucasian twins randomly chosen, except for age and sex distribution, were vaccinated with a 23-valent pneumococcal vaccine. Blood samples were drawn before and after vaccination and the concentration of IgG, IgG1 and IgG2 pneumococcal antibodies was measured using an ELISA technique which only detects type-specific capsular antibodies, since C-polysaccharide antibodies in serum were removed. A significantly closer correlation was found regarding mean IgG and IgG2 antibody concentrations after vaccination in mono- compared with dizygotic twins, and this correlation was seemingly type-specific. Since environmental factors in our study population should not contribute more to the immune response in one type of twins compared with the other, we conclude that genetic factors influence the IgG and IgG2 antibody response to pneumococcal vaccination, and that this influence seems to be type-dependent.     

Pneumococcal antibodies in families with recurrent otitis media

In a recent study it was found that children with recurrent acute otitis media (rAOM), in contrast to healthy children, frequently lack detectable antipneumococcal IgG antibodies against capsular types 6A and 19F. In children with rAOM, the concentrations of antibodies against type 6A polysaccharide remained low even after the period of rAOM had ceased. Antibody levels against various pneumococcal capsular polysaccharides were determined in otitis-prone and healthy members of 19 families. 25 children with a history of rAOM (mean age 7.2 years) and their parents, one of whom in each family had had rAOM during childhood, were investigated. Compared to the parents, the rAOM children had lower concentrations of IgG antibodies against the pneumococcal types 6A, 14, 19F and 23F and of IgA antibodies against type 23F. Compared to their parents, the rAOM children had higher concentrations of IgM antibodies against types 3 and 23F. 'Healthy parents' did not differ from 'rAOM parents' in IgG antibody levels against any of the pneumococcal capsular polysaccharides investigated. The findings indicate that rAOM occurs in individuals with a delayed rather than with a persisting inability to mount an adequate antibody response against the offending pneumococci.     

Specific IgG Subclass Antibody Levels and Phagocytosis of Serotype 14 Pneumococcus Following Immunization

Complement and specific antibody directed against capsular polysaccharide are necessary for efficient phagocytosis of pneumococci. In normal adults, specific antibody to pneumococci is predominantly of the IgG2 subclass. However, the role of IgG2 in bacterial clearance is debatable. We therefore decided to investigate the relationship between specific IgG subclass antibody levels and phagocytosis of serotype 14 pneumococcus, before and after immunization with a pneumococcal capsular polysaccharide vaccine. Specific IgG subclass antibody was measured by an ELISA technique and the effect of serum on phagocytosis of radiolabelled pneumococci by normal polymorphs was determined. We found that in the presence of complement, phagocytosis correlated significantly with both specific IgGl and IgG2 antibody titres( r = 0.547, P = 0.002 and r = 0.464. P = 0.009, respectively). However, in decomplemented sera, the correlation with IgGl antibody was lost, whereas that with IgG2 antibody was strengthened ( r = 0.641. P = < 0.001). The possibility that IgG2 binds to receptors on polymorphs should be considered.     

Production and characterization of monoclonal antibodies specific for types 6 and 19 pneumococcal capsular polysaccharides

The primary IgM and the secondary IgG antibody responses to pneumococcal capsular polysaccharides type 19 (S19) and type 6 (S6) coupled to sheep erythrocytes (S19-SRBC or S6-SRBC) differ in specificity. Although the primary IgM response appears to be totally specific for the pneumococcal cell wall carbohydrate (PnC) which is present in these polysaccharide preparations, the secondary IgG response appears to be completely specific for the immunizing capsular polysaccharide. A library of B cell hybridomas from fusions of splenocytes undergoing a primary response to an S19 preparation consisted entirely of PnC-specific hybrids. Thus, no evidence was obtained for the presence of capsular polysaccharide-specific IgM secreting B cells. IgM and IgG antibody secreting hybridomas were obtained, from fusions of splenocytes undergoing secondary S6- or S19-SRBC responses, to examine the antigen specificity of secondary antibody response of B cells at the clonal level. Many of the secondary IgM hybridomas secreted PnC-specific antibody; however, several S6-specific IgM secreting hybrids were also obtained, demonstrating a previously undetected population of B cells. All IgG secreting hybridomas obtained from S19- or S6-SRBC secondary response fusions secreted capsular polysaccharide-specific antibody, thus confirming the apparent absence of PnC-specific IgG secreting B cells in these responses. This method of immunization and challenge of mice with capsular polysaccharide coupled to erythrocytes, which results in the production of capsular polysaccharide-specific IgG responses, offers a relatively straightforward means to generate monoclonal antibodies specific for pneumococcal capsular polysaccharides.     

Synthetic 6B di-, tri-, and tetrasaccharide-protein conjugates contain pneumococcal type 6A and 6B common and 6B-specific epitopes that elicit protective antibodies in mice

The immunogenicity and protective capacity of Streptococcus pneumoniae 6B capsular polysaccharide (PS)-derived synthetic phosphate-containing disaccharide (Rha-ribitol-P-), trisaccharide (ribitol-P-Gal-Glc-), and tetrasaccharide (Rha-ribitol-P-Gal-Glc-)-protein conjugates in rabbits and mice were studied. In rabbits, all saccharides conjugated to keyhole limpet hemocyanin (KLH) evoked high levels of pneumococcal (Pn) type 6B antibodies that facilitated type-specific phagocytosis. Unlike the disaccharide rabbit antisera, tri- and tetrasaccharide rabbit antisera also reacted with 6A PS in an enzyme-linked immunosorbent assay (ELISA) and promoted phagocytosis of 6A pneumococci. All these rabbit antisera passively protected mice against a Pn 6B challenge. The disaccharide conjugate-induced antiserum, however, failed to protect mice against a 6A challenge. In mice, phagocytic and protective anti-Pn 6B antibodies were only induced by the tetrasaccharide conjugate and not by PS 6B or PS 6B-protein conjugates. These antibodies did not cross-react with 6A PS in ELISA and were unable to phagocytize 6A pneumococci. In conclusion, the disaccharide and tetrasaccharide conjugates already contain epitopes capable of inducing 6B-specific, fully protective antibodies in rabbits and mice, respectively.     

Pneumococcal surface protein A (PspA) is serologically highly variable and is expressed by all clinically important capsular serotypes of Streptococcus pneumoniae.

Pneumococcal surface protein A (PspA) has been shown previously to elicit antibodies protective against pneumococcal infection and to be necessary for full pneumococcal virulence in mice. The protein was originally defined by the two mouse monoclonal antibodies Xi64 and Xi126, which together recognized PspA on 14% of pneumococcal isolates. Some PspA molecules reacted with both antibodies, but most reacted with only one or the other. In the present study we demonstrated that PspA is produced by all pneumococci, confirming our hypothesis that there are variants of PspA which are not detected by Xi64 and Xi126. We produced a rabbit antiserum and five additional monoclonal antibodies specific for PspA for these studies. The rabbit antiserum reacted with each of 95 pneumococcal isolated tested, comprising 16 capsular serotypes. One or more of the seven monoclonal anti-PspA antibodies reacted with 95% (53 of 57) of pneumococcal isolates tested. The specificity of the monoclonal and polyclonal antibodies to PspA was confirmed in two ways: (i) by detection of molecules on wild-type pneumococci that are identical in molecular weight to those detected in Western blots (immunoblots) with Xi64 and Xi126 and (ii) by the use of mutants of Streptococcus pneumoniae that fail to produce PspA or that produce a truncated form of PspA. By using the seven monoclonal antibodies, we observed 31 PspA types among the 57 isolates. When the 53 strains reactive with the monoclonal antibodies were analyzed by capsular type as well as by serologic type and molecular weight of PspA, we observed 50 different clonotypes of pneumococci.     

Assignment of Immunoglobulin G1 and G2 Concentrations to Pneumococcal Capsular Polysaccharides 3, 6B, 14, 19F, and 23F in Pneumococcal Reference Serum 89-SF

We describe standardization of an enzyme-linked immunosorbent assay (ELISA) for measuring immunoglobulin G1 (IgG1) and IgG2 concentrations of antibodies to pneumococcal capsular polysaccharide (Pnc PS). The ELISA uses a human pneumococcal reference serum pool, lot 89-SF, as a reference. IgG1 and IgG2 concentrations were assigned to antibodies to Pnc PS serotypes 3, 6B, 14, 19F, and 23F in 89-SF by ELISA using affinity-purified monoisotypic IgG1 and IgG2 preparations. The sum of IgG1 and IgG2 concentrations in 89-SF agrees well with the previously assigned IgG concentrations. The IgG1 and IgG2 values in 89-SF were used to measure antibodies to Pnc PS 6B, 14, and 23F in adult pre- and postimmunization sera and the sum of IgG1 and IgG2 concentrations correlated well with the IgG values. Furthermore, the IgG2/IgG1 ratio did not affect the detection of IgG1, the isotype usually represented by a lower concentration.     

T-cell dependent response to immune complexes abrogates B-cell unresponsiveness to pneumococcal cell wall polysaccharide.

Although > 90% of B cells from M167 (mu, kappa) immunoglobulin transgenic (Tg) mice express surface immunoglobulin that binds phosphorylcholine (PC), we found that these mice are unresponsive to immunization with pneumococcal cell wall polysaccharide (PnC), a type II thymus-independent antigen that contains PC. However, when the PnC antigen was presented as a complex with TEPC-15 or McPC-603 antibodies (which are specific for PnC), a vigorous immune response occurred in which the Tg mice produced 10-50-fold more anti-PnC antibody than when immunized with antigen alone. Interestingly, MOPC-167, which expresses the VH and VL regions used to encode the transgene antibody, was found to be a relatively poor 'carrier' for PnC, eliciting a weak anti-PnC antibody response in M167 (mu, kappa) Tg mice. In vivo administration of anti-CD4 antibody dramatically reduced the response to TEPC-15/PnC complexes, suggesting that the response is mediated by immunoglobulin (idiotype)-dependent helper T cells. The results indicate that unresponsiveness to PnC is due not to tolerance of the transgenic B cells but rather to the lack of T-cell help resulting from T-cell tolerance to the transgene-encoded idiotype.