Genetic influences on the immune repertoire following tuberculous infection in mice

Differences in the antibody repertoire between B10 and BALB background strains have been found following intraperitoneal infection of mice with Mycobacterium tuberculosis. Western blot analysis showed that B10 sera reacted with only a few antigenic bands, whereas BALB sera reacted with multiple bands, irrespective of the H-2 (b or k) haplotype. The oligo-banded pattern was a feature of live infection, since immunization with the mycobacterial extract in incomplete Freunds' adjuvant (IFA) produced a multi-banded response in both intact and in previously infected B10 mice. The multibanded BALB phenotype was dominantly expressed in (BALB x B10) F1 hybrids. The extent to which antibody levels to individual antigens varied was influenced by the combined effects of background (non-H-2) and H-2 genes: anti-65,000 molecular weight (MW) and anti-71,000 MW IgG levels were high in BALB but absent or low in B10 mice, irrespective of H-2 haplotypes, anti-19,000 MW levels in B10 mice were strongly H-2 controlled, whilst anti-38,000 MW levels were high in all tested strains. Immunoglobulin G1 (IgG1) subclass antibody and splenic interleukin-4 (IL-4) mRNA levels were distinctly lower in B10 than in BALB mice, but in vitro T-cell proliferative responses to mycobacterial antigens did not differ between the tested strains. It is proposed that the limited extracellular release of mycobacterial antigens required to stimulate B cells and/or differential activation of T-cell subsets may explain the narrow antibody repertoire in B10 strains of mice. This may have relevance to the outcome of infection, as bacterial counts were higher in the BALB strains at 10 weeks post-infection.

Elevated antibody levels to mycobacterial 65-kDa stress protein in patients with superficial candidiasis

Antibody levels to the mycobacterial 65-kDa stress protein (mSP65) were determined by ELISA in sera from patients with chronic atrophic oral candidiasis, vulvovaginal candidiasis, Candida albicans-infected or noninfected oral lichen planus, or recurrent aphthous ulceration and from subjects with clinically healthy oral mucosa. The results showed significantly elevated anti-mSP65 antibody levels in patients with oral or vulvovaginal candidiasis and in patients with Candida-infected lesions of lichen planus when compared with patients with noninfected lichen planus or recurrent oral ulceration and with matched healthy controls (P less than .001). Immunoblot analysis showed that the rabbit antiserum that strongly bound to mSP65 cross-reacted only weakly with a homologous band of a soluble C. albicans extract. Moreover, the binding of antibodies from patients with candidiasis to the mSP65 antigen was not inhibited in the presence of Candida extract. In view of the poor serologic cross-reactivity, it seems plausible that the recall stimulation of anti-mSP65-producing B cells could be induced by helper T cells that cross-react with the structurally homologous protein of C. albicans.

Presence of human 65 kD heat shock protein (hsp) in inflamed joints and subcutaneous nodules of RA patients

Monoclonal antibodies to the human homologue of the bacterial 65 kD heat shock protein (hsp) were used to investigate the tissue distribution of endogenous hsp 65 in normal versus rheumatoid synovial tissue, in subcutaneous nodules of patients with rheumatoid arthritis (RA) and in several instances of non-rheumatoid inflammation. A strong reactivity of the anti-hsp antibody was found in the cartilage-pannus junction in rheumatoid joints and in rheumatoid nodules, but not in normal joints or in normal or inflamed kidney or liver (irreversible graft rejection, chronic glomerulonephritis or primary biliary cirrhosis). The findings provide a new hypothetical explanation for a role of T cells reactive with the 65 kD hsp in the generation of both articular and extra-articular lesions in chronic rheumatoid arthritis.

Distribution in tissue sections of the human groEL stress-protein homologue

A monoclonal antibody (ML30) raised against the 65 kDa heat-shock protein of mycobacteria showed widespread staining of sections from standard paraffin-embedded human tissues. The staining had a granular pattern and was particularly marked in cells with abundant mitochondria. Increased staining was observed in the synovial lining, histocytes and in the endothelium of reactive and rheumatoid synovium; it was also increased in the reactive lung alveolar lining. It is suggested that the antibody identifies an epitope in mitochondria of a protein homologous with the groEL heat-shock protein of bacteria.

Differential pattern of T cell recognition of the 65-kDa mycobacterial antigen following immunization with the whole protein or peptides

The 65-kDa stress protein from Mycobacterium bovis (Bacillus Calmette Guérin) elicited T cell proliferation and antibody responses in seven B10 congenic mouse strains with different H-2 haplotypes. To analyze T cell determinants on this antigen, seven peptides corresponding to six predicted T cell epitopes, and one defined B cell epitope were synthesized. Mice were either immunized with the whole antigen and the specificity of the response was ascertained in respect of the six peptides, or mice were immunized with seven of the peptides and tested for proliferative responses to the whole molecule. The results showed that three peptides carried epitopes to which mice responded following injection of the whole molecule and that immunization with two additional peptides could prime for in vitro stimulation with the native antigen. The latter result indicates the feasibility of generating T cell responses to "cryptic" epitopes on proteins by immunizing with peptides. The peptide-specific T cell responses were distinctly influenced by the H-2 haplotype of mouse strains. However, two peptides were recognized by several H-2-disparate mouse strains, and one peptide could be presented by both I-A and I-E molecules. Immunization with several peptides induced a cross-reactive T cell proliferative response to the homologous GroEL protein isolated from E. coli. The amount of cross-reactivity was influenced by the extent of sequence homology between mycobacterial and E. coli proteins and the major histocompatibility complex class II molecule used to present the peptide.

Mechanisms of recrudescence of Mycobacterium bovis BCG infection in mice

The capacity of various immunosuppressive agents to cause a recrudescence of the replication of Mycobacterium bovis BCG in the spleens of chronically infected mice was investigated. The actions of three corticosteroid preparations, cyclosporin A, and anti-T-cell subset monoclonal antibodies were compared. Treatment of mice with hydrocortisone acetate, which depressed the number of splenic lymphocytes and suppressed T-cell responses, most effectively exacerbated the stationary BCG counts, at 4 to 6 months after infection. The magnitude of reactivation was more pronounced in innately resistant CBA/Ca mice than in the susceptible C57BL/6 strain of mice. Splenic bacterial counts were also amplified by anti-L3T4 antibody when the antibody was injected at the chronic phase, whereas cyclosporin A had an effect only during the initial 6 weeks after BCG infection. Cultures of spleen cells from chronically infected mice showed a significant increase in the numbers of viable BCG recovered after 7 days of incubation in the presence of dexamethasone but not with cyclosporin A. The observed differences between the tested immunosuppressive agents indicate that the stationary bacterial counts during chronic BCG infection are maintained by discrete T-cell actions on the infected macrophages.

Molecular study of the T cell repertoire in family contacts and patients with leprosy

The specificity of lymphocyte proliferative responses of 22 family contacts and 7 patients with leprosy were analyzed using Ag fractions from soluble extracts of Mycobacterium leprae and Mycobacterium tuberculosis. Fractions 10-100 kDa m.w. from each extract were separated by SDS-polyacrylamide gel electrophoresis, electroblotted to nitrocellulose membrane and solubilized for use in lymphocyte culture. The main immunogenic fractions for both contacts and patients had m.w. of 12,000 to 22,000, 35,000 to 40,000, and 65,000. Determinants which were either distinct or shared by the two extracts were active in each of the immunogenic fractions. Lymphocyte proliferation following stimulation with separated Ag was found also in five subjects who failed to respond to the whole soluble extracts. Stimulatory synthetic peptides were identified for the 65 kDa protein Ag. This technique has permitted the screening of the T cell immune repertoire for the identification of the immunodominant Ag which merit further purification and molecular characterization.

Molecular study of the T cell repertoire in family contacts and patients with leprosy

The specificity of lymphocyte proliferative responses of 22 family contacts and 7 patients with leprosy were analyzed using Ag fractions from soluble extracts of Mycobacterium leprae and Mycobacterium tuberculosis. Fractions 10-100 kDa m.w. from each extract were separated by SDS-polyacrylamide gel electrophoresis, electroblotted to nitrocellulose membrane and solubilized for use in lymphocyte culture. The main immunogenic fractions for both contacts and patients had m.w. of 12,000 to 22,000, 35,000 to 40,000, and 65,000. Determinants which were either distinct or shared by the two extracts were active in each of the immunogenic fractions. Lymphocyte proliferation following stimulation with separated Ag was found also in five subjects who failed to respond to the whole soluble extracts. Stimulatory synthetic peptides were identified for the 65 kDa protein Ag. This technique has permitted the screening of the T cell immune repertoire for the identification of the immunodominant Ag which merit further purification and molecular characterization.

Levels of antibody to defined antigens of Mycobacterium tuberculosis in tuberculous meningitis

The aim of the study was to develop an antibody immunoassay for tuberculous meningitis with a sensitivity greater than that of the initial bacterial smear while maintaining a 100% specificity. Antibody titers to five purified antigens of Mycobacterium tuberculosis were measured in cerebrospinal fluid by using an enzyme-linked immunosorbent assay technique. Seventy-four patients with tuberculous meningitis (26 culture positive) were compared with 26 patients with purulent meningitis, 69 patients with suspected but excluded tuberculous meningitis, and 29 patients with other neurological diseases. Antibody responses to both the 14-kilodalton (kDa) antigen and lipoarabinomannan were immunodominant, accounting for 74% of those with any antibody titer to a soluble extract of M. tuberculosis. A sensitivity of 61% was achieved (77% for the culture-positive samples) by using immunoglobulin G titers to lipoarabinomannan and the 14-, 19-, and 38-kDa antigens. Thus, estimation of levels of antibody in cerebrospinal fluid to selected mycobacterial antigens would be valuable in the diagnosis of tuberculous meningitis. The possible reasons for the immunodominance of the 14-kDa antigen and lipoarabinomannan in the pathogenesis of tuberculous meningitis are discussed.

Identification of mycobacterial antigens recognized by T lymphocytes

The development of vaccines capable of inducing protective immunity against mycobacterial infection depends in part on the identification of antigenic determinants that activate T cells with antimycobacterial effector function. Various approaches designed to analyze the recognition of mycobacterial antigens by T cells are reviewed. In addition to the established approach of using serologically defined antigens, alternative methods independent of antibody preselection, such as polyacrylamide gel electrophoresis-fractionated immunoblots of mycobacteria, can be used to probe the specificity of the T cell repertoire. Furthermore, the application of recombinant DNA expression combined with that of synthetic peptides whose sequences are predicted to constitute T cell determinants allow the localization of T cell epitopes within a protein. The use of these techniques in defining potentially "pathogenic and protective" T cell epitopes in mycobacteria is discussed.

Association of tuberculosis and M. tuberculosis-specific antibody levels with HLA

In the search for HLA-linked immune response genes that control susceptibility to tuberculosis, we performed HLA typing and measured antibody titers to well-defined Mycobacterium tuberculosis antigenic determinants in 101 patients with sputum smear-positive pulmonary tuberculosis and 64 healthy controls from Surabaya, Indonesia. HLA-DR2 and DQw1 were associated with sputum smear-positive pulmonary tuberculosis (attributable risk = 36% and 39%, respectively), while DQw3 was associated even more strongly with the control group (preventive fraction = 57%). Antibody titers to the TB71 and TB72 epitopes of the 38-kDa protein, present only on tubercle bacilli, were strongly associated with DR2 (Pcorr = .001 and .024, respectively). The association of both the disease and the antibody response to the 38-kDa antigen of M. tuberculosis with Class II HLA genes HLA-DR2 indicates that Ir-gene-mediated regulation of the immune response to this antigen may be of pathogenic significance for the development of sputum smear-positive tuberculosis.

The phenotypic and molecular characterization of Nb2 lymphoma cells activated with IL-2 and human growth hormone

The Nb2 rat lymphoma cell line has the unique property that its growth is dependent on lactogenic pituitary hormones. Cell surface staining with monoclonal antibodies showed expression of class I MHC alloantigens of the RT1u haplotype, but no expression of class II MHC antigens. Staining for differentiation markers was strongly positive with antibodies OX52, W3/13 and OX44. Partial and weaker staining was obtained with CD2, P4/16 and the transferrin receptor. Nb2 cells were negative with CD5, OX40 and CD4, whilst CD8 stained only a minor fraction (1%) and certain variant clones of the cell line. This general pattern of staining is consistent with the phenotype of a small subpopulation of immature T cells. Nb2 cells proliferated in response to recombinant human IL-2, although they did not stain with antibodies against the IL-2 receptor. Enhancement of the stimulation by IL-2 in the presence of a submitogenic concentration of hGH indicated a synergism between these two hormones, and responses were suppressed by a similar dose of cyclosporin A (ID50=2 microg/ml). Although IL-2 could not be identified in culture supernatants, the presence of mRNA for IL-2, IL-2R and IL-4 was demonstrated by dot blot analysis. Finally, evidence that the Nb2 lymphoma is of T-cell lineage was given by Northern blot detection of mRNA for the alpha and beta chains of the T-cell receptor.

Specificity of proliferative response of human CD8 clones to mycobacterial antigens

Human CD8 T lymphocyte clones (TLC) were generated from the pleural effusion of patients with tuberculosis using a protocol that required, in addition to antigen, coculture of purified CD8+ T cells, accessory cells, interleukin 2 (IL2) and anti-CD3-Sepharose. The TLC obtained were stimulated by mycobacterial soluble extracts in an IL2-dependent and MHC class I-restricted manner. When antigen-responsive TLC were screened with extracts from the recombinant mycobacterial library they were found to respond to either the Y3125 (100-kDa) or the Y3111 (71-kDa) lambda gt11 clones. Polyacrylamide gel immunoblot analysis demonstrated that the CD8 TLC responded to fractions with the molecular mass range 27-45 kDa in the Y3125 lysogen and 60-90 kDa in the mycobacterial soluble extract. The specificity of TLC reactive with the Y3111 clone was confirmed using the 71-kDa antigen purified from the same lysogen. These TLC recognized sequences common to the 71-kDa protein derived from mycobacteria, E. coli or a human cell line. Studies of three TLC using antigen-presenting cells of known genetic haplotype indicated that stimulation with both the Y3125 and the 71-kDa antigens were restricted by determinants encoded by HLA-B8.

Orientation of epitopes influences the immunogenicity of synthetic peptide dimers

The immunogenicity of synthetic peptide dimers based on epitope sequences derived from the mycobacterial 65-kDa antigen and the foot and mouth disease virus (FMDV) VP1 protein was examined in inbred mice. The analysis was directed towards the potential helper role of a T cell stimulatory mycobacterial epitope (65-85) with respect to poorly immunogenic sites either from the same molecule (422-436) or from VP1 (141-160). The 65-85 repeat homodimer induced an antibody response in CBA/ca but not in C57BL/6 mice, both nonresponders to the 65-85 monomer, and amplified the antibody response in BALB/c, monomer-responder mice. Analysis of the immunogenicity of hybrid dimers in BALB/c mice showed that the orientation of peptides within the dimer is critical for the extent of the produced antibody response. Only the 422-436/65-85 but not the 65-85/422-436 induced antibodies binding to the 422-436 sequence which was nonimmunogenic when injected either as a monomer or dimer. Despite the striking difference in immunogenicity, both tested hybrid dimers reacted equally in the solid-phase immunoassay with antisera raised to 65-85-dimer or 422-436/65-85 peptides or with a monoclonal antibody to the 422-436 epitope. The described differences in antibody responsiveness also cannot be attributed merely to the extent of T cell stimulation since the proliferative responses were uniformly expressed for all relevant combinations of peptides. Antisera to 65-85 dimer and 422-436/65-85 hybrid also reacted with the native 65-kDa protein. Furthermore, the production of FMDV-neutralizing antibodies in response to the 141-160 (VP1-derived)/65-85 hybrid peptide in 141-160 nonresponder B10.D2 mice also confirmed the helper activity of the 65-85 epitope. Thus, combining heterologous peptides with the N-terminal of the mycobacterial 65-85 sequence may be generally applicable for the potentiation of peptide vaccines.

Specificity of antibodies to immunodominant mycobacterial antigens in pulmonary tuberculosis

A serological survey was performed in groups of patients with active sputum smear-positive or smear-negative pulmonary tuberculosis, healthy household contacts, and controls. Sera were tested for titers of antibodies which bound to each of five purified mycobacterial antigens by enzyme immunoassay and for competition of binding to single epitopes, using six radiolabeled monoclonal antibodies directed toward corresponding molecules. The evaluation of diagnostic specificity was based on a positive score represented by titers above the cutoff point of 2 standard deviations above the mean titer of a control group. For smear-positive samples, the best sensitivity (83%) was achieved by exclusive use of the 38-kilodalton (kDa) antigen or its corresponding monoclonal antibodies. For smear-negative samples, levels of antibodies binding to the 19-kDa antigen showed a lower sensitivity of 62% compared with the control group or 38% compared with the contact group. Titers of antibody binding to the 14-kDa antigen were raised in Mycobacterium bovis BCG-vaccinated contacts, indicating that the greatest potential of this antigen may be in the detection of infection in a population for which tuberculin testing is unreliable. The results demonstrated the differing antibody responses to each of the tested antigens and distinct associations with the stage of infection or disease.

Humoral response to defined epitopes of tubercle bacilli in adult pulmonary and child tuberculosis

In order to investigate the humoral response to tuberculosis in different categories of patients, serum antibody levels to six epitopes of Mycobacterium tuberculosis in adult pulmonary and child tuberculosis were determined. Serum antibody titres were determined by competitive inhibition with radio-labelled murine monoclonal antibodies in 67 adults and 85 children with tuberculosis and in 79 age-matched controls. BCG vaccination (n = 39) and self-healed tuberculosis (n = 11) in adults gave rise to higher antibody titres to TB68, TB23 and TB72 epitopes (all p less than 0.003) when compared to non-vaccinated controls (n = 18). TB68 titres were higher (p = 0.006) in self-healed than in vaccinated adults. Adult sputum-negative patients (n = 15) had higher titres to TB71 (p = 0.015) and ML34 (p = 0.02) epitopes compared to BCG-vaccinated healthy controls, while sputum-positive patients (n = 41) had higher titres to all epitopes tested (all p less than 10(-4]. The diagnostic sensitivity, with a 95% specificity, was best with the combination of probes TB23, TB68, TB72 for sputum-positive (85%) and TB78, ML34 (53%) for sputum-negative patients. Antibody titres in children with tuberculosis were lower than in adult patients; diagnostic sensitivity in histologically or microbiologically proven cases (n = 18) was only 44%, while that in mediastinal lymph-adenitis (n = 67) was 13.5%. This study suggests that the magnitude and specificity of the humoral response to tubercle bacilli varies with site and severity of infection; the implications for pathogenesis or protective immunity are discussed.

The role of host factors for the chemotherapy of BCG infection in inbred strains of mice

Host factors have previously been considered to play a role in the efficacy of "incomplete" antituberculous chemotherapy. We investigated this aspect using a model of intravenous infection with M. bovis-BCG in three inbred strains of mice. Viable splenic counts of bacilli (CFU) were monitored following a three week regimen of rifampicin (R) and isoniazid (H) given either immediately or from three weeks after infection. At the end of the immediate (0-3 weeks) therapy the spleens of all mice were sterile and only a minority of animals had demonstrable CFU's at 23 weeks after infection. However, following the delayed-onset (3-6 weeks) therapy we found a pronounced relapse of BCG growth which was about 10 times higher in CBA/Ca and BALB/C than in C57B1/6 mice. These results indicated that host immunity which developed during the first three weeks after infection may have aggravated the relapse of bacterial growth following chemotherapy. This interpretation was corroborated by the finding that the immunosuppressive drug cyclosporin given concurrently with R/H reduced the splenic viable counts of BCG.

Stress proteins and the immune response to mycobacteria--antigens as virulence factors?

The immune response to mycobacterial infection includes pathogenic as well as protective activities. It is possible that different types of immune responses are associated with recognition of different antigenic determinants. Amongst the antigens which are prominent in antibody and T cell recognition of mycobacteria, we have identified members of highly conserved stress protein families. Mapping of antigenic determinants on stress proteins shows that both species-specific and conserved regions of these proteins can take part in immune recognition. Induction of an immune response to conserved, "self-like", determinants on stress proteins could play a role in the immunopathology associated with chronic mycobacterial infections.

Stimulation by anti-idiotype antibody of murine T cell responses to the 38 kD antigen of Mycobacterium tuberculosis

Rabbit antisera raised against eight monoclonal antibodies (MoAb) binding to distinct mycobacterial antigens revealed individual anti-idiotype specificities following cross-absorption with normal mouse globulin. Only one of these antibodies (Rb71), directed towards an M. tuberculosis-specific epitope on the 38 kD protein antigen was able to stimulate mouse T cell responses which had 'internal image' characteristics. This was demonstrated by anti-Id induced in vitro proliferation of Lyt 1.2+ T cells and the elicitation of delayed type hypersensitivity (DTH) foot pad reactions in antigen stimulated BALB/c mice. The DTH reaction was equally strong in mice sensitized with either M. tuberculosis or M. bovis soluble extracts, thus showing a greater degree of cross-reactivity than antibody binding of the corresponding TB71 MoAb. The immunizing potency of the anti-Id in vivo was demonstrable in three strains of mice following injection of Rb71 emulsified with incomplete Freund's adjuvant. These mice showed 38 kD antigen induced DTH-reactions as well as in vitro proliferation of spleen cells. The display of T cell stimulatory internal image by anti-Id may be interpreted as a consequence of binding specificity of TB71 MoAb of a T cell epitope present in the 38 kD antigen.

Study of idiotypes expressed by monoclonal antibodies to the 35 kD and 12 kD antigens of Mycobacterium leprae

Rabbit antisera were raised against four monoclonal antibodies (MoAb) binding with the 35 kD protein and four MoAb binding with the 12 kD protein antigen of Mycobacterium leprae. Antisera showed idiotype (Id) specificity following cross-absorption with normal mouse globulin. One Id on a single MoAb and another Id shared between three MoAb were identified for each group. Functional studies were carried out with the Rb04 anti [anti-35 kD] specificity. The expression of this Id and paratope in antigen immunized mice was associated with Igh alleles. Inoculation of mice with anti-Id Rb04 induced an 'Ab3' serum response of corresponding Id specificity only when the anti-Id was given in emulsion with incomplete Freund's adjuvant (IFA). Conversely, prior injection of soluble anti-Id inhibited the subsequent Ab3 response to Rb04/IFA. Moreover, the suppressive effect of soluble anti-Id was abrogated by prior injection of 50 mg/kg cyclophosphamide. These results indicate that regulatory mechanisms similar to those involved in antigenic stimulation may explain the stimulatory or suppressive potency of anti-Id antibodies. Finally, the Ab3 responses to the two tested anti-Ids did not contain any antigen binding activity.

Immunopurification of radiolabelled antigens of Mycobacterium leprae and Mycobacterium bovis (bacillus Calmette-Guerin) with monoclonal antibodies

Radiolabelled sonicate of Mycobacterium leprae when examined by SDS-PAGE and two-dimensional gel electrophoresis (2-DE) contained fewer antigens than the comparable sonicate from M. Bovis (bacillus Calmette-Guerin) (BCG). A solid-phase immunopurification assay with anti-M. leprae monoclonal antibodies (MoAb) was used to characterize four of these antigens. Three of the MoAb were M. leprae-specific and with them antigens with apparent molecular weights (Mr) of 12,000 (12K), 18K, and 35K were isolated. On 2-DE, the heavily labelled 12K antigen was heterogeneous with a range in pI of 4.8-5.2. The 35K antigen, which was identified by a conformational determinant, and the 18K antigen were also acidic proteins with pI of 5.4 and 5.1. The fourth antigen was purified from both M. leprae and BCG sonicates and had an Mr of 70K and a pI of 5.1. MoAb reacting with the cell wall protein of M. leprae resulted in separation of multiple bands ranging in Mr from 12K to 65K, rather than the dominant 65K protein seen in immunoblots. A similar pattern was obtained with MoAb that reacted with two cell wall polysaccharide antigens, and these antibodies may have co-precipitated the radiolabelled cell wall proteins. Immunoprecipitates of the M. leprae sonicate with human lepromatous leprosy sera, when analysed by 2-DE, were also found to contain the dominant 12K band and the 35K band. Furthermore, half the radiolabelled BCG antigens were precipitated by the same sera.

Use of anti-idiotypic antibodies as probes for the interaction of TSH subunits with its receptor

TSH is a heterodimeric glycoprotein hormone, whose dissociated subunits are without biological activity. This has precluded the assessment of the relative contribution of each subunit to hormone action. We have raised anti-idiotypes to monoclonal antibodies specific, respectively, for the alpha and beta hTSH subunits. The anti-beta anti-idiotype inhibited 125I-hTSH binding to the beta subunit-specific monoclonal quantitatively, whereas 125I-hTSH binding to the alpha subunit-specific monoclonal was not inhibited by anti-alpha anti-idiotypes, suggesting that only the former is an "internal image" anti-idiotype. Neither of the two anti-idiotypes nor equimolar mixtures thereof inhibited 125I-bTSH binding to thyroid membranes, even though radiolabelled anti-idiotypes showed saturable binding to thyroid plasma membrane which was inhibited 41-65% by bTSH. Each anti-idiotype alone caused 9% inhibition (compared to 50% by NRIgG) of thyroid plasma membrane adenylate cyclase. Equimolar mixtures (125 micrograms/ml IgG of each anti-idiotype) induced enzyme activity equivalent to 85% of that of 250 mU/ml of TSH. The TSH-like action of the two anti-idiotypes was also reflected in their capacity to increase (450% by 250 micrograms/ml IgG compared to normal rabbit IgG) the uptake of 131I into isolated thyrocytes and to promote the organization of such cells into follicular structures. At 250 micrograms/ml, anti-beta anti-idiotype promoted the organization of small follicles and only at a concentration of 500 micrograms/ml did it enhance 131I uptake.

Mapping of T cell epitopes using recombinant antigens and synthetic peptides

Two complementary approaches were used to determine the epitope specificity of clonal and polyclonal human T lymphocytes reactive with the 65-kd antigen of Mycobacterium leprae. A recombinant DNA sublibrary constructed from portions of the 65-kd gene was used to map T cell determinants within amino acid sequences 101-146 and 409-526. Independently, potential T cell epitopes within the protein were predicted based on an empirical analysis of specific patterns in the amino acid sequence. Of six peptides that were predicted and subsequently synthesised, two (112-132 and 437-459) were shown to contain human T cell epitopes. This corroborated and refined the results obtained using the recombinant DNA sublibrary. Both of these regions are identical in M. leprae and M. tuberculosis and are distinct from the known B cell epitopes of the 65-kd protein. This combination of recombinant DNA technology and peptide chemistry may prove valuable in analysis of the cellular immune response to infectious agents.

Characterization of antibody-reactive epitopes on the 65-kilodalton protein of Mycobacterium leprae

Twenty-three monoclonal antibodies (MAbs) prepared in seven different laboratories were studied, all of which recognized the 65-kilodalton (kDa) protein of Mycobacterium leprae as determined by Western blotting or gel radioimmunoassay or both. Fourteen of the MAbs recognized different epitopes, as evaluated by cross-competition studies using radiolabeled MAb and unlabeled inhibitors; the species specificity of these epitopes was defined by nitrocellulose dot blot immunoassays with bacterial sonic extract antigen preparations from 23 species of mycobacteria. Each of the 14 distinct MAbs recognized a 65-kDa protein produced by a lysogenized Escherichia coli Y1089 host containing cloned rDNA which included the gene for the M. leprae 65-kDa protein. Of the 14 distinct MAbs, 1 recognized an epitope found only on M. leprae, and the others recognized epitopes present on as few as 8 or as many as all 23 of the mycobacterial species studied. Identification of these distinct 65-kDa protein epitopes and use of the MAbs which recognize them should assist future structural studies of this protein and characterization of the T-cell reactive and serodiagnostically useful portions of the molecule.

Suppression of delayed hypersensitivity skin reactions to tuberculin by M. leprae antigens in patients with lepromatous and tuberculoid leprosy

Delayed hypersensitivity skin reactions to tuberculin when injected alone or in mixture with antigens of M. leprae were examined in leprosy patients and in healthy controls. The tuberculin reaction was significantly inhibited in more than one half of both LL and BT patients by the soluble extract of M. leprae (leprosin), the leprosin derived 12 kD protein or leprosin depleted of the 12 kD antigen. However, suppression was not found in healthy controls from a leprosy endemic region. These results suggest that multiple M. leprae-specific antigens have an immunoregulatory function. Since suppression was demonstrable not only in LL (leprosin-anergic), but also in BT (leprosin-responder) patients it is of interest that the 'mixed' skin test can discriminate the immune status of at least certain BT patients from that of the infected but self-healing healthy controls. Corollary lymphocyte cultures failed to show any suppression by leprosing of the lymphoproliferative responses to tuberculin.

T-cell activation by anti-idiotypic antibody: evidence for the internal image

Human lymphoproliferative responses to a rabbit anti-idiotypic antibody (anti-Id TB71) and the corresponding mycobacterial protein antigen [38,000 molecular weight (MW)] have been investigated in a number of donors. It was found that responsiveness to anti-Id TB71 correlated with responder and non-responder (four subjects each) status to the 38,000 MW antigen. Furthermore, the induction of T-cell proliferation by both the 38,000 MW antigen and the anti-Id TB71 was dependent on accessory cells. When taken together with the concordance between the 38,000 MW antigen and anti-Id responsiveness, this implies that the 38,000 MW antigen and anti-Id TB71 stimulate related, or at least partially overlapping, repertoires of T cells. This was confirmed by the finding that cloned T cells reactive with the 38,000 MW antigen also proliferated in response to the anti-Id TB71. These observations are readily explained if the anti-idiotypic antibody contains an internal image of, and can therefore mimic, the antigen.

T cell activation by anti-idiotypic antibody: mechanism of interaction with antigen-reactive T cells

It has been shown that the activation of T cells by an anti-idiotypic antibody (anti-Id) TB71 containing an internal image of the corresponding mycobacterial antigen (38 kDa) was achieved by the interaction of anti-Id TB71 with the T cell receptor complex (CD3/Ti). The accessory cell requirement in this response could not be replaced by anti-Id TB71 coupled to Sepharose beads and was not inhibited by Fc receptor blockade. When taken together with the finding that anti-Id TB71-induced proliferation of a T cell clone was restricted by determinants encoded by the major histocompatibility complex, these findings suggested that anti-Id TB71 was presented to 38-kDa antigen-reactive T cells by the same mechanisms as conventional antigenic determinants. That is, both stimulated T cells through the CD3/Ti complex and had to be presented in the context of class II molecules on accessory cells. The finding that the disruption of the integrity of the anti-Id TB71 combining site did not affect T cell responsiveness although antibody binding was ablated implied that anti-Id TB71 may be partially degraded and re-expressed with MHC class II determinants.

Monoclonal antibodies can enhance the biological activity of thyrotropin

In this work we demonstrate that monoclonal antibodies (MABs) to TSH can enhance the biological actions of TSH in vivo. Hypopituitary Snell dwarf mice were injected with TSH (25, 50, or 100 mU/day) alone or complexed with MAB-GC73 once per day for 5 days; control animals received PBS. Radioactive sulfate (35SO4(2-)) was also injected on the fifth day and animals were killed 20 h later. Thyroids were removed for histology, blood taken for T4 estimations by RIA, and 35SO4(2-) uptake into costal cartilage in vivo was measured. In control mice thyroid histology revealed small follicles comprised of small flattened epithelial cells with a high nuclear-cytoplasmic ratio; colloid was dark with little vacuolation. In animals treated with TSH alone there was moderate evidence of activation in most of these features. However, a marked response was noted in animals treated with TSH plus MAB-GC73; characteristically, there was little interfollicular tissue and the follicles, which were large and comprised of cuboidal cells, contained pale, finely vacuolated cytoplasm. Both TSH alone and TSH complexed with MAB-GC73 promoted a significant dose-dependent increase in serum T4 levels. The two higher doses of TSH plus MAB-GC73 promoted a significantly greater increase in serum levels of T4 than that in groups receiving the same dose of TSH alone. Uptake of 35SO4(2-) into costal cartilage showed a significant correlation with serum T4 levels. In similar experiments significant increases in salivary gland epidermal growth factor content of male dwarf mice were observed. This work demonstrated that MAB enhancement of hormone action is not restricted to human GH, suggesting a more general phenomenon.

Analysis of monoclonal antibodies to Mycobacterium leprae by crossed immunoelectrophoresis

Monoclonal antibodies to Mycobacterium leprae were characterized in crossed immunoelectrophoresis and showed markedly different patterns of reactivity with M. leprae lines 2, 7 and 11 respectively. Line 7 corresponds to a cell wall-associated macromolecular complex containing lipid, polysaccharide, and two distinct 36 K and 65 K proteins.

Enhancement of bovine growth hormone activity in vivo by monoclonal antibodies

Monoclonal antibodies (MAbs) prepared against ovine growth hormone (oGH) and recognizing several distinct or related specificities on bovine growth hormone (bGH), have been shown to strikingly enhance the growth promoting properties of the hormone in vivo as determined by 35SO2-4 incorporation in cartilage. The phenomenon is dependent on both hormone and antibody dose and is saturable in the presence of excess antibody. Competition binding analysis between pairs of antibodies has shown that they define distinct antigenic regions on bGH of which one is represented by four MAbs. The most potent growth enhancement was associated with a group of three MAbs (OA11, OA12 and OA13) binding to topographically closely related sites. Another MAb (OA14) with a specificity similar to OA11 and OA13 as defined by competition assay failed to enhance bGH activity. Two antibodies binding to a further two sites (OA15 and OA16) demonstrated modest growth enhancement activity when in complex with bGH, whereas the binding of another antibody (OA17) did not significantly affect hormonal activity. Univalent antibody fragments (Fab) derived from MAb OA11 were equi-potent to the bivalent form of the antibody in the enhancement of bGH activity. Determination of the effects of the different MAbs on the binding of 125I-bGH to liver microsome receptors revealed substantial increase in specific binding (3.5-fold) and is associated with some growth enhancing MAbs. However, not all growth enhancing MAbs increased receptor binding and in the case of one, OA16, clear cut inhibition of receptor binding was observed. Tentative conclusions have been drawn on the possible underlying mechanisms of the MAb mediated enhancement phenomenon.

The 65kDa antigen of mycobacteria-a common bacterial protein?

The 65 kilodalton antigen of Mycobacterium tuberculosis and M. leprae is a well-characterized, strongly immunogenic protein eliciting antibody and T-cell responses in infected patients. Recent studies have disclosed regions of cross-reactivity between the 65kDa antigen and proteins in many other bacterial species. These include the product of the ams gene in E. coli which is involved in the processing of RNA. Here Douglas Young and his colleagues discuss these observations, the significance of the 65kDa antigen and its possible role in the pathogenesis of mycobacterial and other diseases.

Control by H-2 genes of murine antibody responses to protein antigens of Mycobacterium tuberculosis

The genetic control of antibody responses after immunization with Mycobacterium tuberculosis soluble antigens was examined in inbred and H-2 congenic mouse strains. Antibody levels to five distinct epitopes were determined by a competitive inhibition test using radiolabelled murine monoclonal probes. High or low responder antibody levels were associated with either the H-2b (TB23, TB71 and TB72 specificities) or the H-2k (TB68) allele on both B10 and BALB backgrounds. The high response of TB78 specificity associated with the H-2k on the BALB but with H-2b haplotype on B10 background. The phenotype of (C57BL/6 X CBA)F1 hybrids reflected the high response for four and the low or intermediary response for one (TB68) of the tested paratopes. This is the first demonstration of immune response gene control in respect of defined mycobacterial protein epitopes. The implications towards the analysis of pathogenic or protective mechanisms during mycobacterial infection are briefly outlined.

Immunological activity of a 38-kilodalton protein purified from Mycobacterium tuberculosis

A 38-kilodalton (kDa) protein antigen from Mycobacterium tuberculosis was purified by monoclonal antibody TB71-based affinity chromatography. This molecule carries two nonoverlapping epitopes recognized by monoclonal antibodies TB71 and TB72, which are expressed substantially more strongly by M. tuberculosis than by Mycobacterium bovis. However, cross-reactive determinants between these two species were revealed on the 38-kDa protein by a rabbit anti-BCG serum. An immunoradiometric assay based on the TB71 and TB72 antibody pair specifically determined 38-kDa-antigen concentrations in mycobacterial extracts. Antibodies in sera from tuberculosis patients estimated by binding to 38-kDa-antigen-coated microtiter plates were positively correlated with TB72 competing titers. Unlike antibodies, T-cell proliferative responses to the 38-kDa protein were expressed equally by 60% of tuberculosis patients and healthy BCG-vaccinated subjects. Similarly, delayed-type hypersensitivity skin reactions were elicited in both M. tuberculosis- and M. bovis-sensitized guinea pigs. The results suggest the immunodominance of the species-specific B-cell and cross-reactive T-cell stimulatory epitopes.

Potentiation of the somatogenic and lactogenic activity of human growth hormone with monoclonal antibodies

Monoclonal antibodies of certain epitope specificity have been shown to produce a marked dose-dependent enhancement of the somatogenic and lactogenic activity of human GH (hGH). Two antibodies (EB1 and EB2), binding to distinct antigenic determinants and expressed on both hGH and human chorionic somato-mammotrophin (hCS), significantly enhanced the hGH-stimulated uptake of 35S-labelled sulphate into cartilage. Similarly, these antibodies enhanced the lactogenic activity of both hGH and hCS in the pigeon crop sac test. Two hGH specific monoclonal antibodies (QA68 and NA71), defining a further two epitopes, exhibited only modest enhancing or inhibitory activity in these assays, whereas the binding of certain combinations of monoclonal antibodies resulted in either reversal of enhancement or inhibition of hormone activity. Univalent antibody fragments derived from EB1 were as enhancing as the intact antibody indicating that bivalency dependent mechanisms were not involved in the phenomenon. Enhancing monoclonal antibodies were relatively poor inhibitors of 125I-labelled hGH binding to liver microsomal receptors, which is in contrast with their previously described property of potent suppression of hGH interaction with lymphoid cell receptors. It is tentatively concluded that 'restriction' of hormone binding to particular hGH receptors, relevant to somatic growth or lactogenic activity, may play a role in the enhancement phenomenon of hGH in vivo.

Epitope specificity of blood-group-A-reactive murine monoclonal antibodies

Monoclonal antibodies (MABs) towards blood groups A manifested three broad patterns of binding distinguished on the basis of affinities for A1 or A2B phenotype red blood cells and blood group substances. Competitive inhibition of binding of radiolabelled MABs by other unlabelled antibodies and absorption studies with synthetic haptens suggested that GpA specificity was expressed as two topographically related structures, one being the terminal GpA trisaccharide and the second probably involving part of the oligosaccharide backbone. The enhancement of binding of an extremely low-affinity antibody by higher affinity antibodies recognising either epitope indicated a topographic, possibly conformational relationship between these epitopes. It is suggested that only those antibodies that recognise terminal GpA trisaccharides can agglutinate weak A2B cells.

Split tolerance induced by chick embryo thymic epithelium allografted to embryonic recipients

To test the capacity of the epithelial component of the chick embryo thymus to induce tolerance to major histocompatibility complex (MHC) antigens, pre-colonized thymic rudiments were grafted into chick embryonic recipients. Semi-allogeneic or allogeneic transplantations were done between two lines of chickens histocompatible at the MHC locus. Approximately 10% of these thymic chimeras hatched and were studied 3 mo after hatching. Thymic grafts were not rejected by the allogeneic host. The tolerance of chimeric chickens to thymus donor MHC antigens was tested by using a skin graft rejection test and a graft-vs-host (GvH) assay. Chimeric chickens that received an MHC-incompatible thymic graft during the embryonic life tolerated skin graft with the MHC haplotype of the thymus donor. Nevertheless, the lymphocytes within the thymic graft, the host thymus, and the blood were tolerant to the host MHC antigens but were alloreactive in GvH reaction for the MHC antigens of the thymic graft type. These results suggest that the epithelial component of the thymus when taken before the starting of the colonization by hemopoietic precursors and grafted into an early chick embryonic host can induce a tolerance for the MHC determinants involved in allograft rejection but not in the GvH reaction.

Split tolerance induced by chick embryo thymic epithelium allografted to embryonic recipients

To test the capacity of the epithelial component of the chick embryo thymus to induce tolerance to major histocompatibility complex (MHC) antigens, pre-colonized thymic rudiments were grafted into chick embryonic recipients. Semi-allogeneic or allogeneic transplantations were done between two lines of chickens histocompatible at the MHC locus. Approximately 10% of these thymic chimeras hatched and were studied 3 mo after hatching. Thymic grafts were not rejected by the allogeneic host. The tolerance of chimeric chickens to thymus donor MHC antigens was tested by using a skin graft rejection test and a graft-vs-host (GvH) assay. Chimeric chickens that received an MHC-incompatible thymic graft during the embryonic life tolerated skin graft with the MHC haplotype of the thymus donor. Nevertheless, the lymphocytes within the thymic graft, the host thymus, and the blood were tolerant to the host MHC antigens but were alloreactive in GvH reaction for the MHC antigens of the thymic graft type. These results suggest that the epithelial component of the thymus when taken before the starting of the colonization by hemopoietic precursors and grafted into an early chick embryonic host can induce a tolerance for the MHC determinants involved in allograft rejection but not in the GvH reaction.

Antigen presentation by human monocytes: effects of modifying major histocompatibility complex class II antigen expression and interleukin 1 production by using recombinant interferons and corticosteroids

Lymphocyte proliferation in response to monocytes pulsed with an antigenic extract of Candida albicans was measured in vitro and the effects of modifying major histocompatibility complex (MHC) class II antigen expression at the surface of the antigen-presenting cells was investigated. The study shows that no simple correlation exists between changes in MHC class II antigen expression and changes in the effectiveness of antigen presentation. Recombinant interferon-alpha 1 (rIFN-alpha 1), rIFN-gamma and hydrocortisone were found to increase the expression of monocyte class II MHC antigens. In contrast, rIFN-alpha 2 did not increase class II antigen expression although it did increase MHC class I expression. Treatment of monocytes with rIFN-alpha 1, rIFN-alpha 2 or corticosteroids during antigen pulsing resulted in a reduction in the subsequent proliferative lymphocyte response. In all cases this inhibitory effect was restricted to antigen-specific proliferative responses since the polyclonal lymphocyte response to pokeweed mitogen-pulsed monocytes remained unaffected. Only rIFN-gamma treatment of antigen-pulsed monocytes resulted in enhancement of the subsequent specific lymphocyte proliferative response. The suppressive effects of hydrocortisone could not be attributed to its well documented inhibitory effects on arachidonic acid metabolism. The effect of C. albicans antigen, IFN and corticosteroids on interleukin 1 (IL 1) production by monocytes was also investigated. C. albicans antigen alone induced IL 1 production. So too did IFN-alpha 1 and IFN-gamma. IFN-alpha 2 did not induce IL 1 production. Addition of interferons together with C. albicans, however, resulted in the same level of IL 1 productions as with C. albicans antigen alone. Neither antigen nor IFN had any effect on IL 1 action in the thymocyte assay. Corticosteroids did not affect IL 1 production by monocytes but were potent antagonists of IL 1 in the thymocyte proliferation assay. Mitogen-induced thymocyte proliferation was also inhibited by corticosteroids. Pretreatment of monocytes with hydrocortisone followed by washing did not markedly affect their subsequent ability to produce IL 1 neither was it possible to reverse the inhibitory effects of hydrocortisone on antigen presentation by addition of exogenous IL 1. Thus, signals which alter class II MHC antigen expression influence the antigen-presenting capacity of monocytes by a mechanism independent of IL 1. No simple correlation exists between class II expression and antigen-presenting capacity.

Monoclonal antibody-mediated enhancement of growth hormone activity in vivo

This work demonstrates that complexing hGH with monoclonal antibody EBl (MAB-EBl) can produce a striking potentiation of the somatogenic actions of hGH in vivo in Snell dwarf mice. In short-term experiments significant increases in cartilage metabolism and body weight were noted; these responses were dose-dependent for both MAB-EBl and hGH concentration. Increased growth was also observed in long-term experiments. In marmosets where MAB-EBl cross-reacts with endogenous GH, MAB-EBl alone enhanced the actions of endogenous GH. A new perspective may be necessary to incorporate these results into the current concept of antibody action.

Detection of mycobacterial antigen and antibodies in the cerebrospinal fluid of patients with tuberculous meningitis

An immunodiagnostic test for the detection of a soluble nonprotein mycobacterial antigen by reverse passive haemagglutination with IgM murine monoclonal antibody was developed. The test was used to analyse the cerebrospinal fluid of 89 patients with tuberculous meningitis (TBM) from India and 127 control subjects from India and the UK. The antigen was demonstrable in 88% of culture-positive and 73% of culture-negative TBM patients. However, it was also detected in 21% of Indian patients with pyogenic meningitis, and in 8% of Indian and 1% of UK control subjects. Antibodies binding to a soluble mycobacterial extract were detected at low titre in 68% of all subjects with TBM and in 37% of Indian cases of pyogenic meningitis. Because patients with TBM had raised levels of the antigen and of antibodies to the antigen, the possible role of immune complexes in the pathogenesis of the disease is briefly discussed.