Role of extra-esophageal reflux in chronic otitis media with effusion

OBJECTIVES/HYPOTHESIS

Otitis media with effusion (OME) is the most common cause of childhood hearing loss. Despite its prevalence, the enormous health care expenditures resulting from its treatment, and the increasing therapeutic challenges imposed by antimicrobial resistance, very little is known regarding the cellular and molecular immunologic and inflammatory events in this disease process. Extra-esophageal reflux (EER) has been implicated in the pathogenesis of chronic OME. The objective of this study was to confirm that children with OME have EER into the middle ear as measured by the presence of pepsin in middle ear effusions (MEE) removed during tympanostomy tube (TT) placement.

STUDY DESIGN

Prospective, translational, cell biological research study.

METHODS

MEE were obtained from children undergoing TT placement for OME. The fluid was lysed in a urea buffer and the presence of pepsin quantitatively determined by Western blot analysis using a specific antipepsin antibody. The pH of the samples was recorded before lysis.

RESULTS

Pepsin protein was detected in 18 of 32 (56%) samples analyzed, with 12 of 20 (60%) patients having at least one positive sample for pepsin. Pepsin levels ranged from 80 to 1,000 ng/mL. The pH of the samples ranged from 6.0 to 7.6, with a mean pH of 6.8.

CONCLUSIONS

Pepsin was detected in 60% of patients with OME, confirming that EER into the middle ear occurs in these children. The pepsin present would have little or no activity at pH 6.0 to 7.6; however, pepsin is stable below pH 8.0 and thus could be reactivated after a decrease in pH.

Occupational rhinitis due to pepsin

A woman presented work-related rhinoconjunctivitis due to inhalation of pepsin used in a slaughterhouse. Prick tests and conjunctival challenge were positive to pepsin. Serum specific IgE to pepsin was 5.58 kU/L and an IgE-binding band of 43 kDa was detected in SDS-PAGE Immunoblotting. Rhinoconjunctivitis improved clearly when the patient was assigned to another place without contact with pepsin. Pepsin has been previously reported to cause occupational allergic asthma on three occasions. As far as we know, this is the first reported case in which an IgE-immunoblot has been performed.

Kinetic Analysis of Pepsin Digestion of Chicken Egg White Ovomucoid and Allergenic Potential of Pepsin Fragments

BACKGROUND

The allergenic potential of chicken egg white ovomucoid (OVM) is thought to depend on its stability to heat treatment and digestion. Pepsin-digested fragments have been speculated to continue to exert an allergenic potential. OVM was digested in simulated gastric fluid (SGF) to examine the reactivity of the resulting fragments to IgE in sera from allergic patients.

METHODS

OVM was digested in SGF and subjected to SDS-PAGE. The detected fragments were then subjected to N-terminal sequencing and liquid chromatography/mass spectrometry/mass spectrometry analysis to confirm the cleavage sites and partial amino acid sequences. The reactivity of the fragments to IgE antibodies in serum samples from patients allergic to egg white was then determined using Western blotting (n=24).

RESULTS

The rate of OVM digestion depended on the pepsin/OVM ratio in the SGF. OVM was first cleaved near the end of the first domain, and the resulting fragments were then further digested into smaller fragments. In the Western blot analysis, 93% of the OVM-reactive sera also bound to the 23.5- to 28.5-kDa fragments, and 21% reacted with the smaller 7- and 4.5-kDa fragments.

CONCLUSION

When the digestion of OVM in SGF was kinetically analyzed, 21% of the examined patients retained their IgE-binding capacity to the small 4.5-kDa fragment. Patients with a positive reaction to this small peptide fragment were thought to be unlikely to outgrow their egg white allergy. The combination of SGF-digestibility studies and human IgE-binding experiments seems to be useful for the elucidation and diagnosis of the allergenic potential of OVM.

The lupus band: do the autoantibodies target collagen VII?

BACKGROUND

Circulating autoantibodies directed against basement membrane zone (BMZ) components from patients with bullous pemphigoid and epidermolysis bullosa acquisita have been used to identify their target antigen in the skin and to confirm pathogenicity. Although the pattern of immunofluorescence in those diseases is similar to the lupus band, little is known about the origin and pathogenesis of the lupus band. Identifying the binding sites of the lupus band could provide a clue to the nature of the autoantigen that stimulates autoantibody formation in the skin of patients with systemic lupus erythematosus (SLE) and might provide valuable insight into the factors that influence the localization and pathogenicity of the lupus band.

OBJECTIVES

To investigate the relation between the lupus band and the main BMZ components and to identify the target epitopes of autoantibodies deposited in the skin of patients with SLE.

METHODS

Colocalization of the main components of the skin BMZ in nonlesional SLE skin with the lupus band was investigated using conventional immunofluorescence and confocal laser scanning microscopy. The effect of collagenase and pepsin on the expression of the lupus band was correlated with the differential sensitivity of these proteases on the collagenous and noncollagenous (NC) domains of collagen VII. Reactivity of sera from patients with SLE to a complete recombinant human NC1 domain of type VII collagen was then investigated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Near complete colocalization of the lupus band with collagen VII was found in this study, and chemical degradation of the skin attenuated the expression of the lupus band. Collectively, the NC1 domain of collagen VII was suggested as the target antigen of the lupus band, but none of the sera from patients with SLE reacted with recombinant NC1 domain-coated ELISA plates. Alternative explanations for the results of the colocalization of the lupus band with collagen VII are discussed.

CONCLUSIONS

The lupus band colocalized with collagen type VII. The findings of this study ruled out the NC1 domain of collagen VII as a target antigen for circulating autoantibodies in SLE patients with no clinical evidence of blistering. Further studies are required to determine if other regions of collagen VII or another BMZ component is the target antigen for the immunoglobulins of the lupus band.

Polyclonal antibodies for immunochemical determination of human pepsinogens

The human gastric mucosa contains two main groups of aspartic proteinases, pepsin (EC 3.4.23.1) and gastricsin (EC 3.4.23.3), which differ by their structural, kinetic and immunological characteristics. The ratios between human aspartic proteases are important from the diagnostic point of view. Rabbit polyclonal antisera against human pepsinogen A and pepsinogen C (progastricsin) were obtained and tested for clinical purposes. Immunoblotting procedure seems to be a simple and sufficiently sensitive method for qualitative determination of pepsinogens in human gastric mucosa.

Monoclonal antibodies as probes for the changes in antigenicity of bovine and porcine aspartyl proteases with pH

Two monoclonal antibodies, 918(4) and 139(7), directed against either bovine or porcine pepsin, respectively, were retained among 365 positive hybridoma clones. These monoclonal antibodies were characterized by using both indirect and sandwich ELISA. Characterization of these monoclonal antibodies was further performed by the biospecific interaction analysis (BIA-core analysis). Then, they were used as antigenic probes to study the changes in antigenicity of both bovine and porcine pepsins induced by pH. The results demonstrated the importance of the conformational change in both catalytic activities and antigenic determinant accessibility of bovine and porcine pepsins. Furthermore, our results suggest that changes in the conformation due to pH can be detected by specific monoclonal antibodies.

Evaluation of artecoll polymethylmethacrylate implant for soft-tissue augmentation: biocompatibility and chemical characterization

Artecoll polymethylmethacrylate implant (Artecoll) is a combination of polymethylmethacrylate beads suspended in 3.5% atelocollagen and has been designed for use in soft-tissue augmentation applications. The biocompatibility and immunogenicity of Artecoll were evaluated to assess the safety of this product for use in the dermis. To characterize the collagen component, chemical analysis was performed including trypsin sensitivity, differential scanning calorimetry, and pepsin content. Particle size analysis was also performed on the polymethylmethacrylate beads. The ability of this material to elicit an immunologic response was measured in a sensitized and nonsensitized guinea pig intradermal model. In these studies, 24 guinea pigs were injected intradermally with either Artecoll or Zyderm, a bovine collagen product for soft-tissue augmentation. Six sites were evaluated for each material at 3, 7, and 28 days after injection. In the sensitized model, 60 guinea pigs were divided into five groups, and each group received a sensitizing dose (in conjunction with Freund's adjuvant) of Zyderm, Artecoll, or a nonsensitizing dose of the same materials. The fifth group served as a nontreatment control. After the animals were sensitized, they were challenged with intradermal injections of various antigens to evaluate delayed type hypersensitivity reactions. Chemical characterization indicated polymethylmethacrylate beads of varying sizes, including many less than 35 microns, and a vehicle of extensively denatured and impure collagen. In vivo evaluations indicated that Artecoll elicited an immune response in guinea pigs, including delayed type hypersensitivity and antibody reactions. Histological assessment demonstrated particle phagocytosis and transepidermal elimination. Following immunization with Artecoll, guinea pigs were also found to be sensitized to pepsin, an impurity found in the collagen carrier. The biocompatibility of this material was compared with that of bovine dermal collagen (Zyderm collagen implant), which is widely used and accepted as biocompatible. The results of this evaluation indicate that Artecoll polymethylmethacrylate implant has the potential to elicit an immune response in humans, and polymethylmethacrylate beads are susceptible to phagocytosis and elimination.

Antigen processing and presentation by a mouse macrophage-like cell line expressing human HLA class II molecules

Macrophages differ from other antigen-presenting cell types in their potential to take up, process and present particulate antigens as well as proteins and peptides. To study their influence on T cell activation we transfected the mouse macrophage-like cell line P388D1 with human genes coding for the alpha and beta chains of class II molecules (DRA*0101 and DRB1*0401 or DRB1*0404) or with a series of localized DR beta mutants. The transfected cells (TP cells) all expressed DR4 molecules on their surface. Since they stimulated some, but not all, human DR4-reactive T cell clones, some of the resident peptides are evidently similar in mouse and man. Proteins and polypeptides such as pepsin or the human acetylcholine receptor (AChR) alpha 37-181 were also processed correctly by these transfectants and then presented efficiently to other T cell clones. Nearly all the mutants tested could present to the pepsin-specific clone, establishing functional expression of the transfected DR molecules. For the more exacting AChR alpha 144-156-specific T cell clone PM-A1, we confirmed that the single Gly86--> Val mutation in the DR beta chain abolished presentation by two DR4 subtypes. If, however, this same replacement was made in a third variant that has Lys71 (rather than Arg71), the effects were less drastic. This approach could also be used to analyse the contributions of individual substitutions that confer susceptibility to rheumatoid arthritis.

Macrophages, but not dendritic cells, present collagen to T cells

Dendritic cells, such as epidermal Langerhans cells, play a crucial role for the antigen-specific priming of T cells. We have addressed the question whether dendritic cells present collagen, a major protein component in tissues through which dendritic cells migrate, i.e. the basement membrane, dermis, and synovial tissue. Langerhans cells, spleen cells and peritoneal macrophages were compared for antigen-presenting capacity using a panel of mouse T cell hybridomas reactive with different determinants on type II collagen, myelin basic protein, ovalbumin and pepsin. Langerhans cells did not present any of the type II collagen determinants, unless the antigen was administered as a 15-mer peptide, but did present myelin basic protein, ovalbumin and pepsin. Spleen cells and peritoneal macrophages, in contrast, presented all type II collagen determinants. This biased antigen presentation was also observed when Langerhans cells were pulsed with antigen in vivo. The inability to present type II collagen is related to the collagen sequence as such, since both native type II collagen, type II collagen alpha chains, as well as a type II collagen determinant incorporated in type I collagen, were not presented by Langerhans cells. In addition, granulocyte/macrophage colony-stimulating factor-expanded blood dendritic cells displayed the same biased antigen presentation, suggesting that the inability to present collagen is not restricted to dendritic cells localized in epidermis. B cell-deficient mice could prime a type II collagen-reactive T cell response, thus excluding B cells as obligatory antigen-presenting cells for the priming of collagen-reactive T cells. We suggest that neither Langerhans cells nor B cells, but macrophages are the primary antigen-presenting cells in the immune response towards type II collagen.

Protease resistance and binding of Ig light chains in myeloma-associated tubulopathies

Kidney tubule dysfunction and lesions are frequent complications of myeloma, related to unknown properties of the monoclonal light chain. We have analyzed protease sensitivity and binding properties of urinary light chains from four patients with Fanconi's syndrome, 12 with cast nephropathy, and four control patients without myeloma-associated tubulopathy. All light chains were normal-sized, monomeric and/or dimeric, and none was N-glycosylated. Kinetic studies of light chain digestion by pepsin and the lysosomal enzyme cathepsin B showed the generation of a protease-resistant 12 kDa fragment, corresponding to the V domain of the kappa chain in the four Fanconi's syndrome patients; in two out of four the V domain was also completely resistant to trypsin. Western and dot blots revealed similar patterns of reactivity of light chains from patients with the Fanconi's syndrome towards other light chains. Properties of cast-nephropathy light chains were more heterogeneous but clearly differed from those of Fanconi's syndrome: (i) 9 out of 12 were of the lambda-type; (ii) only four yielded a transient 12 kDa fragment after cathepsin B digestion, but all showed some resistance to proteolysis of the entire molecule or a fragment thereof to at least one protease, at variance with control light chains; (iii) they displayed various patterns of reactivity with other light chains; (iv) 7 out of 12 reacted specifically with Tamm-Horsfall protein (THP) by ELISA, in contrast with those of Fanconi's syndrome. In one patient who presented with cast nephropathy and the Fanconi's syndrome, the light chain exhibited both partial resistance of the V kappa domain to cathepsin B and the highest reactivity with THP.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of pepsin with type II collagen (CII) breaks control of CII autoimmunity and triggers development of arthritis in rats

Lewis rats develop arthritis after immunization with heterologous but not homologous rat type II collagen (CII). We have observed that if the rat CII is prepared by pepsin digestion without subsequent extensive purification, it is arthritogenic in Lewis rats. To address whether pepsin in the CII preparations contributed to the development of arthritis and whether this was associated with the induction of an immune response to CII, Lewis rats were immunized with rat CII of various degrees of purity and with various pepsin contents. After immunization with a crude preparation of CII, containing relatively large amounts of pepsin, Lewis rats developed arthritis with an incidence of 80% together with a strong anti-CII autoantibody production. Further purification of the CII on DEAE-Sepharose, which removes pepsin, eliminated the arthritogenic properties and the capacity to activate CII-specific B cells. Likewise, lathyritic CII, prepared without pepsin, induced neither a CII-specific immune response nor arthritis. If, however, pepsin was added to non-arthritogenic batches of rat CII, arthritis appeared at an incidence of 40%. By using an ELISPOT technique to detect antigen-specific interferon-gamma-producing T cells and antibody-producing B cells, the immune response to CII and pepsin can be evaluated. Eleven days after immunization with lathyritic CII and pepsin, a B-cell response towards both CII and pepsin was seen. Pepsin-specific T cells were also seen at day 11, but CII-specific T cells did not appear until day 14 after immunization. In addition, a weak CII-specific proliferative response of the T cells could be demonstrated at day 14 but not at day 11 or 12. These data show that pepsin plays an important role in the triggering of a CII-specific immune response. We suggest a carrier-hapten mechanism where pepsin acts as a carrier and CII as a 'hapten' which will activate CII-specific B cells. Subsequently these CII-specific B cells will break the T-cell tolerance and evoke a T-cell-mediated immune response towards CII.

Anti-type II collagen ELISA. Increased disease specificity following removal of anionic contaminants from salt-fractionated type II collagen

The purification of type II collagen, for the detection of anti-type II collagen antibodies by ELISA procedures, involves removal of proteoglycans by guanidine-HCl, followed by pepsin solubilisation and salt fractionation. However, type II collagen purified in this way may contain contaminants, despite the apparent purity on SDS-polyacrylamide gels. In this paper we demonstrate how additional purification by DEAE chromatography reduces the degree of background binding in the type II collagen ELISA, leading to an increase in disease specificity. The contaminants included proteoglycan and bound serum IgG from both rheumatoid arthritis (RA) patients and healthy controls in ELISA. Furthermore, positive correlations were observed in the sera (n = 24) between degree of reactivity to the contaminants and to (1) purified proteoglycan (r = 0.50, P = 0.01) and (2) pepsin (r = 0.65, P = 0.001). Thus, inadequate purification of type II collagen produces false positive reactions in the collagen ELISA and gives rise to a high background. A lack of specificity has been frequently associated with this assay.

Mobilization of gelatinase-rich granules as a regulatory mechanism of early functional responses in human neutrophils

Components involved in superoxide anion production (cytochrome b) and in cell adhesion processes (CD11b, CD11c, CD18), two early functional responses of neutrophils during acute inflammation, are intracellularly located in resting human neutrophils. We have found a correlation between secretion of gelatinase and overexpression in the plasma membrane of CD11b, CD11c, CD18 and cytochrome b upon cell activation. Gelatinase and lactoferrin were parallely released after cell activation with different stimuli, but a better correlation between antigen up-regulation and gelatinase release was obtained. Total translocation of the intracellular pool of these mobilizable molecules to plasma membrane was achieved under conditions that induced total degranulation of the gelatinase-rich granule population, whereas 50% and 90% of the lactoferrin-containing secondary granules and peroxidase-containing primary granules, respectively, remained unfused. These results suggest a mechanism by which neutrophil function can be regulated through mobilization of gelatinase-rich granules, which can be considered as a subpopulation of secondary granules.

Natural human monocyte gelatinase and its inhibitor

Gelatinases produced by stimulated peripheral blood monocytes were detected by substrate zymography and were compared with those derived from tumor cells. Stimulated monocytes were found to produce an 85 kDa gelatinase which co-migrated upon electrophoretic separation and cross-reacted in immunoprecipitation experiments with a phorbol ester inducible metalloprotease from human tumor cells. The intact natural gelatinase (85 kDa), a high molecular weight and complexed gelatinase as well as a proteolytic fragment (25 kDa) were purified by substrate- and antibody-affinity chromatography techniques. Aminoterminal sequence analysis showed that natural monocyte gelatinase occurs as a truncated form of tumor cell gelatinase/type IV collagenase. Furthermore, peripheral blood monocytes were found to also produce a tissue inhibitor of metalloproteases (TIMP). TIMP was co-purified with gelatinase on gelatin sepharose and identified by microsequencing. The balanced and regulated production of gelatinase and TIMP might be important in monocyte migration and tissue remodeling.

Cartilage proteoglycan-induced arthritis in BALB/c mice. Antibodies that recognize human and mouse cartilage proteoglycan and can cause depletion of cartilage proteoglycan with little or no synovitis

Human fetal cartilage proteoglycan (PG) induces the development of an erosive polyarthritis and spondylitis in BALB/c mice. We have examined the properties of 3 monoclonal antibodies (MAb) to human fetal cartilage PG isolated from immunized mice that cross-react with mouse cartilage PG. Compared with sera from arthritic mice, which contain antibodies reactive with keratan sulfate, MAb 202 (IgG1) reacted only with a protein-related epitope that is distributed on both hyaluronic acid-binding and chondroitin sulfate-attachment regions. MAb 813 (IgG1) reacted with the same fragments and recognized an epitope with the immunologic characteristics of keratan sulfate. MAb 945 (IgM) remains to be further characterized. Introduction of hybridomas secreting MAb 202 and MAb 945 into irradiated mice resulted in the loss of PG from articular cartilage and from growth plate cartilage (with MAb 202 only), as revealed by a loss of staining with toluidine blue. There was no synovial hyperplasia with MAb 202, but some hyperplasia and mononuclear cell infiltration was seen with MAb 945. This was accompanied by the binding of immunoglobulins to articular cartilage, as demonstrated by immunofluorescence. The hybridoma secreting MAb 813 produced no cartilage changes or synovitis, and there was no immunoglobulin binding to cartilage. Polymorphonuclear leukocyte infiltration was never observed with these antibodies. These studies indicate that MAb reactive with mouse cartilage PG can cause the depletion of PG from hyaline cartilage by mechanisms that may be both complement dependent and complement independent. Antibodies may serve to release and expose PG antigen to immune cells, as well as causing a loss of the mechanical properties of cartilage that are PG dependent.

Analysis of type II collagen-reactive T cells in the mouse. I. Different regulation of autoreactive vs. non-autoreactive anti-type II collagen T cells in the DBA/1 mouse

The T cell reactivity against type II collagen (CII) was analyzed in the collagen-induced arthritis-susceptible mouse strain DBA/1. It was shown that the proliferative response in lymph node cells from rat CII-immunized mice was mainly directed against a foreign determinant present on all heterologous CII tested but not on autologous CII. A T cell line with this reactivity reacted with high sensitivity with CII and the determinant was mapped to the CB11 fragment of CII. A weak autoreactive response could be detected in the primary cultures using high concentrations of mouse CII and this reactivity remained after several stimulations with high concentrations of rat CII but not with low concentrations of rat CII. A similar response against mouse CII but with only limited cross-reactivity to rat CII was seen when culturing the cells with mouse CII as antigen. The optimal concentration for the autoreactive response was always more than 100-fold higher than for the response of the T cells specific for heterologous CII. An anti-CII T cell response could also be detected in spleen cells from unimmunized mice and the strongest response was obtained using autologous CII. These results suggest that T cells recognizing self CII are normally activated in the DBA/1 mouse and possibly as a consequence exhibit a clonal anergy pattern with a weak proliferative response only at high concentrations of CII.

Induction of anti-pepsin antibodies after immunization with pepsin-extracted collagen

Immunization with pepsin-extracted human type II collagen purified by different precipitation steps, although not showing any contamination with the enzyme on SDS-polyacrylamide gel electrophoresis, resulted in the generation of antibodies to the enzyme in addition to an immune response to collagen. These antibodies could be removed by immune absorption on a pepsin affinity column, leaving reactivity to type II collagen unaltered. High performance liquid chromatography on hydroxylapatite columns indicated that pepsin remained associated with the collagen molecules even after repeated precipitation and coeluted with a fraction of the collagen preparation. These results demonstrate that pepsin-extracted collagens may contain minimal amounts of the enzyme. On immunization, these impurities may induce the formation of unwanted antibodies, which might simulate a false specificity of the antibody preparation.

Characterization of gelatinase from pig polymorphonuclear leucocytes. A metalloproteinase resembling tumour type IV collagenase

The metalloproteinase 'gelatinase' stored in the granules of pig polymorphonuclear leucocytes has been purified in the latent form. The enzyme is secreted as an Mr 97,000 proenzyme that can be activated in the presence of 4-aminophenylmercuric acetate (APMA) by self-cleavage to generate lower-Mr species, of which an Mr 88,000 form was the most active. Trypsin-initiated activation generated different Mr gelatinases of much lower specific activity. Activation was slowed but not prevented by the presence of the tissue inhibitor of metalloproteinases, TIMP. The activated gelatinase formed a stable complex (Mr 144,000) with TIMP, in a Zn2+- and Ca2+-dependent manner, and complex formation was inhibited by the presence of the substrate gelatin. Similar to the human granulocyte gelatinase, the organomercurial-activated pig enzyme degraded gelatin and TCA and TCB fragments of type I collagen, as well as elastin and types IV and V collagen. The degradation of type IV collagen was shown, both by polyacrylamide-gel electrophoresis and by electron microscopic analysis, to generate 3/4 and 1/4 fragments as described for mouse tumour type IV collagenase. Furthermore, an antiserum raised to mouse type IV collagenase recognized the pig granulocyte gelatinase. An antiserum to the pig polymorphonuclear leucocyte gelatinase recognized other high-Mr gelatinases, including those from human granulocytes, pig monocytes and rabbit connective tissue cells, but not the Mr 72,000 enzyme from connective tissue cells. These data suggest that there are two distinct major forms of gelatinolytic activity that also cause specific cleavage of type IV collagen. These enzymes are associated with a wide variety of normal connective tissue and haemopoietic cells, as well as many tumour cells.

Auto-anti-idiotype antibody against anti-thyroglobulin auto-antibody in humans

Anti-idiotype antibodies (Anti-Id Ab) are believed to normally exert a form of feedback control on Ab production. An abnormality in this network might lead to excess Ab production. To detect the abnormalities in immunoregulation in autoimmune thyroid disease, we tried to demonstrate anti-Id Ab to anti-thyroglobulin antibody (ATA) and to correlate them to the clinical course of disease. We developed two assays, one based on the binding of anti-Id Ab to ATA (Id) and a second on the inhibitory activity of anti-Id Ab in the reaction of human thyroglobulin (hTG) and ATA. We could not demonstrate anti-Id Ab in either assay. Possibly anti-Id Ab to ATA is not formed sufficiently to be detected in our assays, or is only present in specific phases of the course of autoimmune thyroid disease. During studies of anti-Id Ab we found "pepsin site" Ab in patients and normal subjects. We developed a new solid phase radioimmune assay for this Ab, an antibody which reacts with antigens exposed on IgG when F(ab')2 fragments of IgG are prepared. The incidence of this Ab did not differ between patients and normal subjects. IgG from patients with autoimmune thyroid disease which contained high levels of anti-pepsin site Ab, did not show any specificity for ATA (Id), nor did it inhibit the reaction between hTG (Ag) and ATA (Id). The importance of this anti-F(ab')2 antibody remains to be determined, but it does not represent an anti-Id Ab.

Autoreactive B cells in normal humans. Autoantibody production upon lymphocyte stimulation with autoantigen-xenoantigen conjugates

Mononuclear cells (MNC) from the blood of healthy individuals cannot be stimulated in vitro with the soluble autoantigen thyroglobulin (Tg). However, when Tg or pepsin fragments of Tg were coupled with a carrier protein, tetanus toxoid (TT), MNC from four healthy TT vaccinated individuals responded to the carrier-autoantigen conjugates by generating anti-Tg antibody forming cells (AFC), as shown in a spot enzyme-linked immunosorbent assay. Generation of anti-TT and anti-Tg AFC after stimulation with the conjugates required the donors to be boostered with TT. The autoantibodies were exclusively of the IgM class, in contrast to the carrier-specific anti-TT antibodies, which were predominantly of the IgG isotype. Activation of normal B cells to anti-Tg production was dependent on the presence of T cells in the cultures and required physical linkage of carrier and autoantigen: no anti-Tg AFC could be detected when MNC were stimulated with uncoupled combinations of Tg and TT. The autoreactive and the carrier-reactive B cells exhibited almost identical conjugate dose-response profiles, which suggest that they responded in a similar way to regulatory signals. These findings indicate that normal blood B cells are competent to respond to the autoantigen Tg in conjunction with signals originating from xeno-antigen-stimulated T cells.

Human anti-F(ab')2 antibodies and pepsin agglutinators react with Fv determinants

Affinity-purified human IgG anti-tetanus antibody was subjected to papain and then pepsin digestion, and residual fragments retaining antibody activity were re-isolated by adsorption and elution from Sepharose-tetanus toxoid columns. Both Fab' and Fv fragments isolated by gel filtration showed strong reactivity with anti-F(ab')2 antibodies. Failure of tetanus toxoid to completely block reactivity of anti-F(ab')2 antibody with anti-tetanus Fv fragments indicates that these antibodies react with framework antigens within variable antibody regions.

Characterization of immune complexes and immunoglobulin G antibodies reactive with neutrophils in the sera of patients with Felty's syndrome

These studies were performed to determine the relative contribution of immune complexes or antibodies reactive with PMNs to the elevated levels of IgG PMN-binding activity seen with sera from some patients with Felty's syndrome. Twenty-one sera from 19 patients with Felty's syndrome were fractionated by gel filtration on Sephadex G-200. Fourteen of the sera had elevated levels of IgG PMN-binding activity as measured by a sensitive IgG-specific antiglobulin inhibition technique. Ten of the G-200 excluded pools and eight of the G-200 IgG pools had levels of IgG PMN-binding activity greater than 2 S.D. above the mean value for normals.Significant correlations were observed between the levels of IgG PMN-binding activity in the sera and the values for both the G-200 excluded pools (r = 0.51) and the IgG pools (r = 0.69). These data suggested that both soluble immune complexes and antibodies reactive with PMNs contributed to the elevated serum levels of IgG PMN-binding activity seen with sera from some patients with Felty's syndrome. Further evidence for the presence of PMN-binding immune complexes in the sera of patients with Felty's syndrome was the strong correlation between the values of serum IgG PMN-binding activity and the levels of immune complexes as detected by C1q binding (r = 0.71) or analytical ultracentrifugation (r = 0.60). Studies of G-200 excluded samples adsorbed with human IgG coupled to Sepharose 4-B indicated that immune complexes containing rheumatoid factors contributed only in part to the increased levels of IgG PMN-binding activity and of C1q-binding activity. Confirmation of the presence of antibodies reactive with neutrophils was the finding of significantly greater binding to PMN with F(ab')2 fragments of IgG from four sera of patients with Felty's syndrome compared to F(ab')2 from normal sera. Adsorption studies suggested that the PMN-reactive antibodies did not possess rheumatoid factor activity.

Immune responses to some proteins and synthetic polypeptides in inbred strains of rats

The antibody responses to DNP-bovine gamma globulin, bovine gamma globulin, human serum albumin, ovalbumin, pepsin and five synthetic polypeptides were examined in strains of inbred rats representative of eight common major histocompatibility complex (RTI) haplotypes. With each antigen the antibody response varied considerably among strains, and the data provide many potential strain and antigen combinations with which to study the genetic control of the immune response.

[Immunochemical characteristics of pepsinogen-pepsin isoforms from the gastric mucosa of the pig, Sus scrofa]

Electrophoretic and immunoelectrophoretic studies reveal three isoforms of pepsinogen and pepsin which differ in their immunochemical properties. Activation of pepsinogen to pepsin at pH 2 does not affect antigenic properties of the isoforms of the enzyme. Some of the isoforms of commercial pepsin do not exhibit immunogenic properties, although reveal the enzymic activity. This finding indicates that immunochemical and biochemical determinants are located in different parts of isoenzyme molecules.

Cathepsin D agglutinators and neutral protease agglutinators in rheumatoid arthritis. II. Production of CDA and NPA by rheumatoid synovium and phagocytosis of CDA by synovial phagocytic cells

Tissue culture methods demonstrated the production of agglutinators against the cathepsin D site in IgG (CDA) and a neutral protease site in IgG (NPA) by rheumatoid synovial tissue. Seven of 11 specimens from seropositive and 2 of 7 specimens from seronegative RA patients were positive for CDA, whereas 2 of 11 specimens from seropositive and 1 of 7 specimens from seronegative patients were positive for NPA. None of the 6 control specimens was positive for both types of agglutinators. Chromatography of two synovial tissue incubates showed that the CDA were of the IgG type. By the immunofluorescence technique, plasma cells containing CDA were demonstrated in rheumatoid synovial tissue and draining lymph nodes of rheumatoid joints. The staining for CDA in the synovium was different from the staining for pepsin agglutinators in adjacent sections. Phagolysosomes containing CDA were found in synovial exudate cells from rheumatoid patients as well as in phagocytosing lining cells and macrophages of the sublining layer of rheumatoid synovial tissue. These findings suggest that antibodies directed at hidden antigenic sites in IgG revealed by endogenous proteolysis take part in the immune reaction and in the inflammation of rheumatoid joints.

[Antigenic properties of the proteolytic enzymes of the gastrointestinal tract]

Antigenic properties of crystalline pepsin, trypsin and chymotrypsin were studied in 9 rabbits immunised with these enzymes. Production of antibodies and their titres were investigated by means of the reaction of the precipitation in testing tubes and immunoelectrophoresis. The most clear antigenic properties were revealed in trypsin, and they were the weakest in pepsin. Low titres of the antibody to pepsin were, probably, due to denaturation of its molecule at physiological values of pH immunisation. Absence of cross-reactions of antisera to trypsin and chymotrypsin with pepsin solutions may be due to considerable structural differences of the antigenic determinants of pepsin from those of trypsin and chemotrypsin. However, antisera to trypsin and chemotrypsin do develop cross-reactions with respective enzymes and there were may be due to a similarity between structures of their antigenic determinants.