IgE and mast cell response on intestinal allergen exposure: a murine model to study the onset of food allergy

OBJECTIVE

Allergic reactions to food are characterized by enhanced allergen-specific IgE serum levels and the activation of intestinal mast cells. Here we describe a murine model for the onset of food allergy and the role of cytokines in the regulation of food-induced IgE responses.

METHODS

Mice were primed systemically with low doses of alum-precipitated ovalbumin. Subsequent intragastric challenge led to enhanced sensitization.

RESULTS

Compared with baseline ovalbumin-specific IgE levels before challenge (0.23 +/- 0.06 optical density [OD] units), ovalbumin-challenged mice showed significantly elevated IgE levels (0.86 +/- 0.23 OD units) after intragastric challenge, which were not observed in control animals (0.29 +/- 0.06 OD units). IgE levels mirrored intestinal mast cell activation, measured by decreased histamine levels in duodenal specimens, in ovalbumin-challenged mice (92.6 +/- 7.9 ng/0.1 gm tissue weight) but not in saline-challenged mice (135.4 +/- 18.3 ng/0.1 gm tissue weight), compared with baseline levels (141.1 +/- 4.1 ng/0.1 gm tissue weight). Changes in IgE and histamine levels after intragastric challenge could be blocked by treating the animals with neutralizing antibodies against IL-4 or IL-10. Although it is generally accepted that ingestion of food allergens leads to a state of immunologic unresponsiveness (i.e., oral tolerance), it is shown here that low-dose systemic priming followed by intragastric challenge leads to sensitization instead of unresponsiveness.

CONCLUSIONS

Our murine model shows an important correlation between TH2 cytokines, IgE production, and histamine release. Hence, this in vivo model provides a useful tool with which the complex mechanism underlying sensitization to food allergens can be studied.

Vacuolating cytotoxic activity of Pasteurella multocida causing haemorrhagic septicaemia in buffalo and cattle

The toxic activity of Pasteurella multocida strains which cause haemorrhagic septicaemia (HS) in buffalo and cattle was examined in a mouse model. Mice were injected intraperitoneally with 10(2) cells of P. multocida serotype B:2,5. Electron microscopy of peritoneal macrophages obtained 6 h after injection revealed strong induction of cytoplasmic vacuolation, macrophage lysis and death. In vitro experiments with the mouse macrophage cell line RAW 264 incubated with cultures of various HS- and non-HS-associated strains of P. multocida or with culture supernatants revealed macrophage vacuolation when HS-associated strains were used. On pre-incubation of the strains with antiserum obtained from buffalo infected with P. multocida serotype B:2,5 no vacuolation was observed. These results are indicative of the presence of vacuolating cytotoxic activity in HS-associated strains of P. multocida.

Evaluation of monoclonal antibodies with specificity for human IgA, IgA subclasses and allotypes and secretory component. Results of an IUIS/WHO collaborative study

51 monoclonal antibodies (McAb) with putative specificity for human IgA, the IgA subclasses, Am allotypes or secretory component (SC) were evaluated for immunoreactivity and specificity by nine laboratories employing immunodiffusion, agglutination, immunohistological assays, immunoblotting and direct binding and competitive inhibition enzyme immunoassays. McAbs specific for IgA PAN (n = 24), IgA1 (n = 7), IgA2 (n = 3), IgA2m(2) (n = 2), non-IgA2m(2) (n = 4) and SC or secretory IgA (n = 5) were identified that were immunoreactive and specific in the assays employed. The McAbs identified as IgA- or SC-reactive were shown to be non-reactive to human IgG, IgM, IgD, IgE, kappa and lambda by direct binding and competitive inhibition immunoassays. Interestingly, no McAbs with restricted specificity for IgA2m(1) were identified. Some McAbs displayed higher affinity and/or better performance in one or several of the assay groups. The IgA- and SC-specific McAbs identified in this international collaborative study have potential as immunochemical reference reagents to identify and quantitate monomeric and polymeric IgA in human serum and secretions.

Albumin and immunoglobulin levels in nasal secretions of patients with nasal polyps treated with endoscopic sinus surgery and topical corticosteroids

BACKGROUND

Nasal polyposis is principally treated by surgery, which may be combined with administration of topical corticosteroids to postpone or prevent recurrences.

OBJECTIVE

In this study endoscopic sinus surgery and subsequent use of topical corticosteroids (budesonide) for 1 year was evaluated.

METHODS

Clinical data of 41 patients with nasal polyps were evaluated, and their nasal secretions were compared with those of 26 healthy persons (control subjects).

RESULTS

The patients had much higher initial total protein, albumin, IgM, secretory IgA (S-IgA) (p < 0.001 for all), and IgG concentrations (p < 0.05) than the control subjects. Treatment resulted in a significant decrease of S-IgA (p < 0.001) within 6 months. IgM and IgG concentrations decreased more slowly (p < 0.001 and p < 0.05 at 1 year, respectively). IgE levels decreased, but we could not demonstrate significance. Relative to total protein levels, the albumin and S-IgA levels decreased within 6 months (p < 0.005 and p < 0.001, respectively). The excretion of all proteins remained higher in patients than in the control subjects, even after 1 year of topical corticosteroid treatment. Clinical evaluation showed slightly higher S-IgA levels in patients with an IgE-mediated allergy than in those without such a condition, and the recurrence rate was highest in the former group (75% vs 48%).

CONCLUSION

The data support the hypothesis that inflammatory reactions in the nasal mucosa play a role in the pathogenesis of nasal polyps but also suggest an additional causative factor.

Macrophage depletion in the rat after intraperitoneal administration of liposome-encapsulated clodronate: depletion kinetics and accelerated repopulation of peritoneal and omental macrophages by administration of Freund's adjuvant

The purpose of this study was to develop a method for the depletion of macrophages from the peritoneal cavity and the omentum of the rat. Rats received two intraperitoneal injections (at days 0 and 3) with liposome-encapsulated clodronate (dichloromethylene bisphosphonate: Cl2MBP-liposomes). This treatment resulted in complete elimination of mature tissue macrophages (ED2-positive macrophages) from the peritoneal cavity and the omentum within 2 days. The elimination included the strongly ED2-positive spindle-shaped cells of the omental membrane. Repopulation of the omental ED2-positive macrophages was not seen within the next 23 days. Whereas ED2-positive macrophages were completely depleted, few ED1-positive cells remained and repopulation of ED1-positive cells was faster. The treatment further depleted macrophages from the spleen, especially from the red pulp, parathymic lymph nodes and liver. Freund's incomplete adjuvant administered one day after the last injection of Cl2MBP-liposomes considerably accelerated repopulation in the omentum. The protocol described might be used to investigate the contribution of mature tissue macrophages to the induction of immune responses, drug metabolism and the elimination of intestinal tumours.

Reticulum cells in the ontogeny of nasal-associated lymphoid tissue (NALT) in the rat

This study concerns the ontogeny of reticulum cells (RC) in the nasal-associated lymphoid tissue (NALT) of Wistar and Brown-Norway rats. A panel of monoclonal antibodies (mAb) directed against RC in peripheral lymphoid organs (antibodies ED10-ED15) was used, together with a recently developed antibody ED17, which recognizes macrophages and Langerhans cells. Early in embryogenesis, staining with common connective tissue markers, ED14 and ED15, was found. ED17-positive cells were present before cells positive to ED1, a pan-macrophage marker, or Ia glycoproteins were observed. The first differentiation of reticulum was seen at the day of birth, when ED10 recognized a distinct area in the nasal mucosa. The first T-lymphocytes were found at the same time. Two days after birth, B-cells and ED11-positive cells were present in the NALT area. Fourteen days after birth, T- and B-cell compartments were recognizable. ED10 was found predominantly in the T-cell area and ED11 was mainly confined to the B-cell compartment. We conclude that the development of the NALT is closely accompanied by the phenotypic specialization of the reticulum. This suggests that the reticulum plays an important role in the compartmentalization of NALT tissue and in the retention of lymphocyte subsets within these compartments.

Eosinophils in nasal polyps and nasal mucosa: an immunohistochemical study

Immunohistochemical staining was performed at the time of endoscopic sinus surgery (ESS), after 6 months, and after 1 year on nasal polyps and biopsy specimens of the macroscopically unaffected mucosa of the middle and inferior turbinate bones of 46 patients with nasal polyps. During the follow-up period the patients were treated with topical corticosteroids. At time of ESS significantly more BMK13+ and EG1+ (pan eosinophil markers) and EG2+ (activation marker) eosinophils were found in the polyps than in the macroscopically unaffected mucosa of the middle and inferior turbinate bones of the patients. In the middle and inferior turbinate bones of 10 healthy subjects no EG2+ (activated) eosinophils were detected, whereas low-to-moderate numbers of BMK13+ and EG1+ eosinophils were seen in these specimens. This emphasizes that eosinophils play a role in the pathogenesis of nasal polyps. Compared with numbers at ESS, after 6 months and 1 year of follow-up, lower numbers of BMK13+, EG1+, and especially of EG2+ eosinophils were found in recurrences of polyps and in the macroscopically unaffected mucosa of the middle and inferior turbinate bones of the patients. The decrease in number of EG2+ (activated) eosinophils is an indication of a reduced local inflammatory reaction, and could be an important factor in postponement of recurrences of nasal polyps.

The in vivo antibody response in rat gut-associated lymphoid tissue (GALT) after immunization with bacterial polysaccharide antigen

Gut mucosal immune responses to bacterial polysaccharide antigen in rats were investigated in vivo. Rats were immunized with pneumococcal polysaccharide type 3 (PPS-3) via different routes, i.e. in the Peyer's patch (iPP), in the colon (ic), in the peritoneal cavity (ip), and intravenously (iv). The development of specific antibody-forming cells (AFC) and their isotypes in the intestinal mucosa, gut-associated lymphoid tissue (GALT), mesenteric lymph nodes (MLN) and spleen were studied by immunohistochemistry. Furthermore, the serum antibody levels were measured by enzyme-linked immunosorbent assay (ELISA). The results showed that iPP immunization evoked high numbers of anti-PPS-3 AFC of the IgA isotype in the mucosa of the small intestine and in the PP. On the contrary, the ic route did not elicit a mucosal response, though a few AFC were found in the MLN and spleen. Following ip priming, a specific IgA response was found, especially in MLN and spleen, and a low response was detected in the villi. A high response was found in the parathymic lymph nodes (PTLN). Iv immunization gave rise to the development of AFC in the spleen, particularly of the IgM isotype. We failed to induce mucosal responses to PPS-3 antigen in the colon, irrespective of the route of immunization.

Peritoneal cell labelling: a study on the migration of macrophages and dendritic cells towards the gut

In this study the migration of peritoneal cells was investigated by a fluorescence labelling technique. We found that peritoneal cells migrate to the subcapsular sinus and medulla of the parathymic lymph node (PTLN) and paratracheal lymph node (PTrLN). It was also observed that fluorescence labelled cells possibly granulocytes, macrophages and dendritic cells were found in the B cell follicles of Peyer patches and the dome area after intraperitoneal (ip) labelling. The implication of the migration of antigen presenting cells to the gut on the mucosal immune response is discussed.

Mechanisms of white cell reduction in red cell concentrates by filtration: the effect of the cellular composition of the red cell concentrates

The effect of platelets on the removal of white cells (WBCs) from 16 to 24-hour-old red cell (RBC) concentrates by filtration was studied. RBC concentrates with various concentrations of platelets and WBCs were filtered on a cellulose acetate column filter and on three polyester flatbed filters. The microscopic study revealed that lymphocytes and most monocytes were captured in the smaller pores of the fiber network, irrespective of the brand of filter, the type of filter material, or the prefiltration platelet amount in the RBC concentrates. In contrast, efficient granulocyte depletion depended on granulocyte-platelet interaction and on the filter material. In the presence of platelets, granulocytes were captured in the top part of the column filter or in the coarse layers of two of the flatbed filters, where platelets covered the fibers. Platelet depletion of the RBC concentrates prior to filtration diminished the contribution of these parts of the filters to granulocyte capture. A larger part of the column filter or the fine layers of the flatbed filters were now required for granulocyte capture. In one of the flatbed filters, granulocyte-platelet interaction occurred mainly in the fine layers, which ended in blockage of this filter after the filtration of variable volumes (250-600 mL) of standard RBC concentrates. A quantitative estimation of the effect of platelets on the WBC-reduction capacity found that all three flatbed filters had a highly significant decrease (p = 0.001) in WBC-reduction capacity for platelet-depleted or buffy coat-depleted RBC concentrates, as compared with standard RBC concentrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical aspects and distribution of immunologically active cells in the nasal mucosa of patients with nasal polyps after endoscopic sinus surgery and treatment with topical corticosteroids

Clinical parameters of 72 patients who were operated upon for nasal polyps were evaluated as well as biopsy specimens of the mucosa of the middle and inferior turbinates of 41 of these patients. Biopsies were taken at the time of endoscopic sinus surgery (ESS), after 6 months and after 1 year in 23 patients. During the follow-up period the patients were treated with topical corticosteroids (budesonide). At the time of ESS significantly more CD8+ (suppressor/cytotoxic) cells than CD4+ (helper/inducer) cells were found in the middle and inferior turbinates. At 6 months significantly more CD4+ cells were found than at the time of ESS, whereas at 1 year the number of CD4+ cells had decreased and was lower than at 6 months. These data support the theory that the occurrence of nasal polyps is associated with T-cell-dependent disturbances. Clinical evaluation revealed that most of the patients with chronic airway obstruction had better pulmonary functions postoperatively or required less medication for lung disease. These findings show that ESS combined with topical corticosteroids has a positive effect on upper and lower respiratory tract pathology.

The role of nasopharyngeal lymphoid tissue

Nasal-associated lymphoid tissue (NALT), which comprises paired lymphoid organs in the nasopharynx of rodents, is the principal mucosal lymphoid tissue of the respiratory tract. As described in this review, NALT bears certain similarities to the Peyer's patches of the intestine but the two differ remarkably in morphology, lymphoid migration patterns and the binding properties of their high endothelial venules (HEV).

Electronmicroscopic examination of white cell reduction by four white cell-reduction filters

The mechanisms of white cell (WBC) reduction in 16-hour-old CPDA-1 red cell (RBC) concentrates by filtration on a column filter and on three different flatbed filters were studied by electron microscopy, with special emphasis on cell-to-cell interaction, cell damage, and interaction of blood cells with the material. Generally, lymphocytes were removed by mechanical sieving and monocytes by adherence and mechanical sieving. Granulocyte depletion occurred by mechanical sieving, direct adhesion to the fibers, and indirect adhesion to activated and spread platelets. In the column filter, most granulocytes were captured by adhesion. In the coarse layers of two of the flatbed filters, indirect adhesion was most prominent, whereas direct adhesion was most prominent in the other flatbed filter. For the most part, granulocytes were captured by direct adhesion in the fine layers, but in one flatbed filter, capture apparently occurred by mechanical sieving. The results of this study suggest that the efficiency and the mechanism of WBC reduction depend on the physicochemical characteristics of the non-woven materials in the filters as well as the cellular composition of the RBC concentrates.

Effects of limited reduction on disulfide bonds in human IgA1 and IgA1 fragments

Human IgA occurs in body fluids as monomers, dimers and secretory IgA (sIgA). Besides the cysteine residues in intra-domain, inter-chain and inter-subunit disulfide bonds IgA molecules contain several cysteine residues with unknown function and reactivity. Limited reductions on serum IgA1 and secretory IgA1 with glutathione revealed that four cysteine residues per monomer or subunit were part of labile bonds. Six cysteine residues were reduced in F(ab')2 fragments and about three in Fc fragments, but none in Fab fragments, indicating that the labile bonds occur in the Fc fragment. By SDS-PAGE analyses of reduced proteins labile inter-alpha chain bond(s) were detected in F(ab')2 and F(abc)2 fragments but not in Fc fragments and intact IgA1, thus showing the importance of the CH3 domains for the structural stability of the hinge region. Nine cysteine residues per IgA1 were reduced with 0.01 M DTT and a large proportion of the IgA1 myeloma proteins formed half-molecules consisting of an alpha- and a light chain, but sIgA1 remained intact. This indicates a relative stability of heavy to light chain and inter-subunit bonds. Reductions in the presence of 2% SDS disrupted several intra-chain bonds. Binding studies with (CH2)2-specific monoclonal antibodies, which detect an epitope expressed only on IgA molecules with disulfide linked alpha chains, were in accordance with the SDS-PAGE results. A new model for the location of labile and more stable disulfide bonds is discussed.

Comparison of five different filters for the removal of leukocytes from red cell concentrates

The leukocyte depletion capacity and performance of 5 filters designed for filtration of red cell concentrates (RCC) were compared by counting leukocytes, measuring red cell volumes and by histological examination of the filters after use. To eliminate interdonor differences, 5 buffy-coat-poor RCC were pooled (in each of 10 experiments) and subsequently split up into the original bags. The RCC were passed over the Cellselect filter, a column filled with cellulose acetate, and over flat-bed polyester filters: the Cellselect Optima, the Pall RC 50, the Leukostop and the Sepacell R-500. The filtration was shortest with the Pall RC 50 (p less than 0.001 compared to the other 4 filters). Leukocyte removal was most effective with the cellulose acetate filter (p less than 0.01 compared to the other 4 filters) followed by the Cellselect Optima polyester filter (p less than 0.02 compared to the remaining 3 filters). Residual leukocytes did not exceed 50 x 10(6) for any brand of filter. Red cell recovery was similar for all 5 filters with mean values from 86.1 to 89.2%. The leukocyte numbers, counted in Türk's solution or in propidium iodide, gave comparable values in hemocytometers applying light microscopy or fluorescent microscopy, respectively. Histological examination showed that lymphocytes were mainly removed by trapping, whereas granulocytes showed a variable pattern: adhesion in presence of platelets or trapping.

Lymphoid tissue in rat oral mucosa: structure and function

Lymphocyte and macrophage/dendritic cell populations in the oral cavity of the rat were studied by immunohistochemistry. Furthermore, the reactivity of the oral mucosa towards antigen and its position in the mucosal immune system was investigated by staining antibody-forming cells and comparing serum and saliva antibody titres. Although numerous lymphocytes and non-lymphoid cells were present in the oral mucosa, organized lymphoid tissue could not be found. The majority of the lymphocytes are T cells, particularly of the T-helper phenotype. Macrophages were found only in the connective tissue, whereas dendritic cells also occurred in the epithelium. The possible functions of the cells in the different sites of the oral mucosa are discussed. Antibody-forming cells were mainly detected in the draining superficial and posterior cervical lymph nodes and in the submandibular glands. The roles of the various compartments of the oral mucosal immune system are discussed with particular reference to the epithelium and connective tissue as induction sites, the draining lymph nodes as sites of proliferation and differentiation, and the submandibular glands as effector sites.

Ontogeny of reticulum cells in the rat intestine and their possible role in the development of the lymphoid microenvironment

Ontogeny of reticulum cells (RC) in the rat intestine in relation to the development of the gut-associated lymphoid tissue (GALT) was studied using a panel of monoclonal antibodies (mab) directed against RC in peripheral lymphoid organs, ED10-ED15. The mab ED10 specific for RC in the spleen T cell area, recognized an epitope on gut RC, which cells seem to be involved in the influx and accumulation of lymphocytes in the lamina propria and in Peyer's patches (PP) and proximal colonic lymphoid tissue (PCLT). The mab ED11 which recognizes RC in the T cell area and B cell follicles of spleen, stained follicular dendritic cells (FEC) in the B cell area of the mesenteric lymph node (MLN), PP and PCLT. The ED11 expression occurs earlier and reveals stronger staining in MLN as compared to those in PP and PCLT, suggesting the prominent role of MLN in the generation and proliferation of B cells in the gut mucosal immune system. The mab ED13 specific for RC in the B cell area of the lymph nodes, stained the basement membrane of the epithelium overlying PP and PCLT, and high endothelial venules (HEV), suggesting that this might be involved in providing the microenvironment for the development and differentiation of follicle-associated epithelium, and facilitating lymphocyte traffic. The mab ED12 specific for RC in the paracortex of peripheral lymph nodes, gave a diffuse nonspecific staining in the gut, whereas mab ED14 and ED15 are markers for common connective tissue cells. We conclude that the gut RC are morphologically and phenotypically heterogenous. ED10+, ED11+, and ED13+ RC are probably involved in the development of the gut lymphoid microenvironment.

Immunoglobulin concentrations in nasal secretions differ between patients with an IgE-mediated rhinopathy and a non-IgE-mediated rhinopathy

Nasal secretions from patients with an IgE-mediated rhinopathy, patients with a non-IgE-mediated rhinopathy, and healthy control subjects were collected with a newly developed direct aspiration system. Total protein, albumin, secretory IgA (sIgA), IgE, IgG, and IgM concentrations were measured in the nasal secretions to detect whether the nasal pathology is reflected in nasal secretion protein concentrations. It was found that protein and immunoglobulin concentrations in nasal secretions were inversely related to amount of secretion in the nasal cavity. Both patients' groups had a significantly higher sIgA to protein ratio than the healthy control subjects. Furthermore, patients with an IgE-mediated rhinopathy had significantly higher sIgA and IgM to total protein ratios in their nasal secretions than patients with a non-IgE-mediated rhinopathy. Probably these differences are due to changes in immunoregulation.

The in situ immune response of the rat after intraperitoneal depletion of macrophages by liposome-encapsulated dichloromethylene diphosphonate

This study concerns the contribution of peritoneal macrophages in vivo to local and systemic immune responses in the rat. Peritoneal macrophages as well as macrophages in the draining parathymic lymph nodes were selectively eliminated by intraperitoneal inoculation of dichloromethylene-diphosphonate-containing liposomes. This depletion resulted in an enhanced immune reaction to intraperitoneally administered trinitrophenyl keyhole limpet haemocyanin in the parathymic lymph nodes, as demonstrated by the higher numbers of specific anti-TNP antibody-forming cells in macrophage-depleted animals than in control animals from day 5 after immunization. The immune reaction peaked at day 7 and remained high until day 10. Specific antibody-forming cells were found occasionally in the mesenteric lymph nodes and spleen, but not in the mucosa of the gut or in the bronchus-associated lymphoid tissue. An elevated immune reaction found in parathymic lymph nodes associated with the depletion of local macrophages by liposome treatment indicates a regulatory role of peritoneal macrophages in local humoral immune response.

Nasal secretions from patients with polyps and healthy individuals, collected with a new aspiration system: evaluation of total protein and immunoglobulin concentrations

This study was designed, first, to test a new system for aspiration of human nasal secretions and, secondly, to evaluate protein and immunoglobulin concentrations in these secretions at different levels of secretory activity. The direct aspiration system combines the advantages of minimal irritation of the nasal mucosa with the facility to determine concentrations per gram of secretion. The total protein and immunoglobulin concentrations were inversely related to the amount of secretion obtained. Variations in fluid secretion throughout the day may be responsible for this relationship. The inverse relationship was much more significant in patients with nasal polyps, in which much higher concentrations were found, than in healthy subjects. Ratios of immunoglobulin to total protein were independent of the amount of secretion obtained. Compared to the controls, the ratios of IgM and IgG to protein in the secretions of the patients were significantly increased. The secretory immunoglobulin A to total protein ratios were only slightly higher in the patients' secretions.

Mucosal and systemic antibody formation in the rat after intranasal administration of three different antigens

In order to study the role of nasal-associated lymphoid tissue (NALT) in the local nasal immune response, rats were immunized intra-nasally with either of the following trinitrophenylated (TNP) antigens; the thymus-dependent keyhole limpet haemocyanin (KLH), or the thymus-independent lipopolysaccharide (LPS), or with the particulate (thymus-dependent) sheep red blood cells (SRBC). Primary responses hardly occurred, while only TNP-KLH elicited a considerable secondary response. The major responding organ was the posterior cervical lymph node. Specific antibody-forming cells (AFC) occurred in the medulla and were mainly of the IgA or IgG isotype. Hardly any specific AFC were found in NALT or the surrounding mucosa. Intranasal immunization evoked no antibody response in the lung. Ample anti-TNP antibodies could be detected in the sera of animals, primed and boosted with TNP-KLH or TNP-LPS. No specific serum antibodies occurred after immunization with TNP-SRBC. The results are discussed in view of the immunological defence in the upper respiratory tract.

Lymphocytes and nonlymphoid cells in human nasal polyps

Immunohistochemical stainings were performed on polyp specimens of 48 patients and on mucosal biopsy specimens of the middle and inferior turbinates of 23 and 28 patients, respectively. Significantly more CD8+ (suppressor/cytotoxic) than CD4+ (helper/inducer) cells were found in the polyps. The number of CD2+, CD4+, and CD8+ lymphocytes in nasal polyps were very similar to the number in the macroscopically unaffected mucosa of the middle turbinates, whereas scores in the inferior turbinates were lower. In healthy subjects, the differences were smaller. CD22+ B cells were detected in varying numbers in the polyps in more or less organized clusters. Significantly more HLA-DR+ cells were found in polyps and middle turbinates than in the inferior turbinates. Eosinophils were found in moderate to large numbers in polyps of 77% of the patients. Mast cells and plasma cells were detected in moderate numbers, whereas neutrophils were found in 35% of the patients. In the middle and inferior turbinates varying but small numbers of eosinophils, mast cells, plasma cells, and neutrophils were found. In considering these findings, the role of chronic inflammation with T cell-dependent disturbances is discussed with regard to the pathogenesis of nasal polyps.

Histologic and immunohistochemical studies on the preparation of white cell-poor red cell concentrates: the filtration process using three different polyester filters

Three third-generation white cell (WBC)-depletion filters based on polyester layers with decreasing pore size were investigated. In the coarse layers, unaggregated granulocytes, monocytes, and platelets and aggregates of these cells were captured in close contact with the fibers. This indicates that the depletion of granulocytes, monocytes, and platelets in the coarse layers of the filters is due in part to activation and adhesion with the formation of cell clusters on the fibers. In Filter I and Filter II platelets were not found in the fine layers, whereas in Filter III, 70 percent of the platelets were detected as unaggregated platelets on the fibers of the fine layers. More than 95 percent of the lymphocytes captured in the three filters occurred as single cells in the fine layers, and over 60 percent of these could be recovered. This suggests that the depletion of lymphocytes depended on trapping of the cells in the fiber network. All three filters captured HLA-DR-positive lymphocytes in the top layers, a finding that supports earlier reports that the transfusion of filtered red cell concentrates reduces HLA alloimmunization. More lymphocytes and granulocytes were found in the last layer of Filters II and III than of Filter I. Therefore, the risk of white cell leakage is probably lowest for Filter I. Red cells were found as red cell aggregates in the fine layers of Filters I and II, whereas almost no red cells were detected in Filter III. It was shown that the three filters studied were similar in their removal of WBCs, but differed in their mechanisms of removal.

The effects of Peyer's patches inactivation in the rat on the development of antibody-forming cells to intestinal antigen

The effects of Peyer's patch (PP) inactivation on local and systemic immune response in rats was investigated. A cauterization method has been developed to inactivate PP. Animals were primed intraperitoneally or intragastrically with trinitrophenyl-keyhole limpet haemocyanin (TNP-KLH) one day before cauterization, and were challenged intraintestinally two weeks later. The secondary immune response in the spleen, mesenteric lymph node (MLN) and intestinal villi was studied by immunohistochemistry. Histological observations on PP after inactivation showed that most T cells in the interfollicular area had disappeared, as had B cells in the follicle. T cells repopulated PP much slower than B cells. Complete recovery of PP occurred no earlier than 2 weeks after inactivation. The immunization experiments revealed higher numbers of anti-TNP antibody-forming cells (anti-TNP AFC) of IgM, IgG and IgA isotypes in the spleen of the PP-inactivated animals than in the controls. Very few anti-TNP AFC were found locally in the lamina propria of the intestinal villi or in the MLN in both groups. It is suggested that PP play a role in the regulation of systemic immune responses against intestinally-administered thymus-dependent antigen. Moreover, inactivation of PP could alter the antigen uptake by gut epithelium and the local antigen processing. As a result, an increased amount of antigen could reach the spleen eliciting a higher immune response.

Anti-TNP-forming cells in rats after different routes of priming with TNP-LPS followed by intranasal boosting with the same antigen

To study the reactivity of nasal-associated lymphoid tissue (NALT) and its position in the mucosal immune system, rats were intranasally challenged with 200 micrograms TNP-LPS. Priming had occurred 15 days previous to the challenge with the same antigen and dose, either intranasally, intratracheally, subcutaneously in the cheek or intraperitoneally. The number of anti-TNP antibody-forming cells (AFC) was determined in various tissues using the conjugate TNP/alkaline phosphatase. Generally, anti-TNP AFC were predominantly found in the posterior cervical lymph nodes, while NALT contained hardly any such AFC. The highest response in the posterior cervical lymph nodes occurred on day 5, after subcutaneous priming and intranasal boosting. This also evoked peak responses in several other tissues. The highest response in spleen and lung occurred on day 7 after intraperitoneal priming and intranasal boosting. Irrespective of the immunization route, IgA was the least produced isotype in the spleen as compared to antigen-specific IgG and IgM. In the posterior cervical lymph nodes, besides specific IgG and IgM, a considerable proportion of specific IgA was produced. All four immunization routes yielded anti-TNP antibodies in serum. As for the non-lymphoid cells, the intratracheal-intranasal immunization protocol induced an increase in pulmonary macrophages on days 3 and 5. The immunological role of lung macrophages is discussed.

Histological and immunohistochemical studies on the preparation of leukocyte-poor red cell concentrates by filtration: the filtration process on cellulose acetate fibers

A histological and immunohistochemical investigation of slices from the Cellselect leukocyte filter showed that the capture of lymphocytes within these filters depended on trapping of the cells in the cellulose acetate fiber network more than on adherence. Probably, additional mechanisms played a role in granulocyte removal. Microaggregates of granulocytes and platelets were found at the top of the Cellselect leukocyte filter. Therefore, it is likely that granulocyte and platelet removal, at least in part, is due to the formation of cell clusters on the surface of the fibers. Although a part of the original, nonfiltered, leukocytes already showed morphologic characteristics of cell necrosis, more necrotic leukocytes were detected within the filter.

The localization of macrophage subsets and dendritic cells in the gastrointestinal tract of the mouse with special reference to the presence of high endothelial venules. An immuno- and enzyme-histochemical study

This study concerns the distribution of macrophages and dendritic cells (DC) in the gastrointestinal tract of the mouse. Heterogeneity of macrophage population was found by using the MOMA-1, MOMA-2, ERTR-9, Mac-1 and F4/80 monoclonal antibodies. MOMA-1, ERTR-9, Mac-1 and F4/80+ cells were detected mostly at the villous cores in the lamina propria of the villi, whereas MOMA-2+ cells were primarily found around the crypts at the base of the villi. These MOMA-2+ cells revealed a granular appearance throughout the cytoplasm and displayed a strong acid phosphatase (AcPh) activity. Few MOMA-2+ cells were seen at the top of the villi in the epithelium. Although MOMA-1 and ERTR-9+ cells have similar morphology and the same distribution patterns in the lamina propria, they are likely different populations, because in Peyer's patches (PP), MOMA-1+ cells were present, whereas ERTR-9+ cells could not be detected. Both populations displayed AcPh activity. Strongly stained Mac-1+ cells were abundantly seen in the lamina propria of the small intestine. F4/80+ cells were rare. NLDC-145+ cells with AcPh activity and weak Ia staining were also found. In the PP-associated villi and in the T-dependent area of PP, dendritic NLDC-145+ cells, which were strongly Ia positive, were detected. MIDC-8+ cells were found only in the T-dependent area. Few NLDC-145+ cells (dendritic cells) were found in the upper part of the oesophagus. These cells were also stained with the MIDC-8 antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphoid and non-lymphoid cells in nasal-associated lymphoid tissue (NALT) in the rat. An immuno- and enzyme-histochemical study

Lymphocyte and macrophage subpopulations and the stroma of mucosa-associated lymphoid tissue in the nasal cavity of the rat were examined by application of immunohistochemical and enzyme histochemical methods to cryostat sections. Nasal-associated lymphoid tissue was composed of a loose reticular network with lymphocytes and macrophages, covered by epithelium. The epithelium was infiltrated with B cells. T helper (W3/13-positive) and T suppressor/cytotoxic or large granular cells (OX8-positive), ED1-positive macrophages and Ia-positive cells. The B cell areas were populated by B cells, immunopositive for surface IgM or IgG. B cells with surface IgA or IgE were rare. Germinal centres were found infrequently. T helper cells were scattered throughout the B cell area. A few ED1-positive macrophages and ED5-positive follicular dendritic cells were observed. Strong Ia staining (mostly of B cells) was found in this area. The T cell areas contained T helper and T suppressor/cytotoxic cells in about equal amounts, and numerous ED1-positive macrophages. ED1 staining was also found in the subepithelial area. Numerous ED1-, ED2- and ED3-positive macrophages were found in the border between the lymphoid mass and the surrounding connective tissue. A few non-lymphoid cells showed weak acid phosphatase or non-specific esterase activity. The morphological observations suggest that nasal-associated lymphoid tissue plays an important role in the first contact with inhaled antigens.

Lymphocytes and nonlymphoid cells in the nasal mucosa of patients with nasal polyps and of healthy subjects

Immunohistochemical stainings were performed on biopsy specimens of the middle and inferior turbinates of the nasal mucosa of 14 patients with nasal polyps and 16 healthy subjects. Significantly more CD8+ (T suppressor/cytotoxic) cells than CD4+ (T helper/inducer) cells were found in the lamina propria of the middle and inferior turbinates of patients with nasal polyps and in the inferior turbinate of healthy subjects. The middle and inferior turbinates of healthy subjects contained significantly more CD4+ cells than the middle and inferior turbinates of patients with nasal polyps. CD19+ B cells were hardly detected in the patients and healthy subjects. More HLA-DR+ cells were found in the middle than in the inferior turbinate, especially in the patients. Varying but small numbers of eosinophils, neutrophils, mast cells, and plasma cells were found in patients and healthy subjects. The possible role of CD4+, CD8+, and HLA-DR+ cells in the nasal mucosa is discussed with regard to the pathogenesis of nasal polyps.

An immunohistochemical study on the postnatal development of rat nasal-associated lymphoid tissue (NALT)

This study concerns the development of nasal-associated lymphoid tissue in the rat, using immuno- and enzyme-histochemical staining techniques on cryostat sections. Nasal-associated lymphoid tissue is present at birth as a small accumulation of mainly T lymphocytes and nonlymphoid cells; B cells are rare. Distinct areas of T and B cells appear at 10 days after birth; by that time high endothelial venules are also observed. Intra-epithelial lymphocytes are present, most of them being T-helper cells. ED1+ macrophages are seen throughout the tissue. The proportion of ED1+ cells does not change during ontogeny. ED2+ cells (tissue macrophages) are present predominantly at the border between the lymphoid tissue and the surrounding connective tissue, in all age-groups. ED3+ mononuclear cells are scattered throughout the nasal-associated lymphoid tissue of young animals. Later on, the ED3+ cells migrate into the border-area between lymphoid and connective tissue. Ia+ non-lymphoid cells in the nasal lymphoid tissue increase in number during ontogeny. Only a few of them show acid phosphatase activity, indicating that the proportion of classical scavenger macrophages is low. Some of them may be antigen presenting (dendritic) cells. Ia+ dendritic cells also occur between the epithelial cells. Moreover, some epithelial cells express the Ia marker.

Binding of human IgA1 and IgA1 fragments to jacalin

Interaction of jacalin, an N-terminal galactose specific lectin, with human IgA1 and IgA1 fragments was investigated. IgA1 and all galactose containing fragments bound to jacalin-Sepharose, including Fab fragments containing only the galNac linked to serine-224 and Fc fragments containing four gal-galNac sequences. These data indicate that both the galNac and gal-galNac sequences can interact with jacalin. Jacalin precipitated IgA1 and the fragments F(abc)2, F(ab')2 and Fc in agar gel and from solutions. It also precipitated Fab' fragments in agar gel. Jacalin did not precipitate Fab fragments significantly. This suggests that, except for the single binding site on the Fab fragments containing the galNac linked to serine-224, jacalin itself also has a limited number of sites to interact with N-terminal galactose residues. ELISA studies revealed that intact IgA1 had a lower jacalin binding capacity than F(abc)2 fragments which lack CH3 domains, than F(ab')2 which lack the CH2 and CH3 domains, and than Fc fragments containing four gal-galNac sequences. This led to the conclusion that part of the galNac or gal-galNac sequences in intact IgA1 molecules are inaccessible to interaction with jacalin. Cleaving the C-terminal domains off may have induced a reorientation of the hinge region structure, including the orientation of the carbohydrate units.

Intra-epithelial lymphocytes and non-lymphoid cells in the human nasal mucosa

Immunohistochemical staining of biopsy specimens was used to investigate the occurrence of lymphocyte subsets and non-lymphoid cells within the epithelial layer of the human nasal mucosa. The CD19 (B cell) marker was not expressed on the intra-epithelial lymphocytes, whereas the pan T cell marker CD2 was varyingly detected. The HLA-Dr antigen was abundantly present on epithelial cells, lymphocytes, and non-lymphoid cells. The latter are probably dendritic or Langerhans' cells. The findings stated above were the same in patient and control samples. In biopsy sections of 9 ear, nose, and throat patients, many CD8-positive (T suppressor/cytotoxic) cells and very few weakly stained CD4-expressing (T helper/inducer) cells were present. Quantification on single-cell preparations showed an average of 67% of the lymphocytes to be CD2 positive, 73% to be CD8 positive, while only 12% of the lymphocytes expressed the CD4 antigen. In control sections CD8 was similarly present as in patient sections, and, in addition, some clearly stained CD4-positive cells were seen.

Effect of serum albumin on the recovery of human IgA1 from immobilized jacalin

Published methods for affinity purification of human IgA1 on immobilized jacalin are based on binding through galNac residues in the IgA1 hinge region. The present study shows that in addition to this galNac-dependent binding an 'alternative' binding mechanism, involving protein-protein interactions, is operative. Moreover, human (HSA) and bovine (BSA) serum albumins were also observed to interact with jacalin through the 'alternative' mechanism, though much more weakly than IgA1. HSA and BSA did not interfere with the galNac-dependent binding of IgA1, but inhibited the 'alternative' binding of IgA1 to jacalin-Sepharose, probably by competition. Thus, IgA1 from serum samples was almost completely bound through the galNac-dependent mechanism, but part of the IgA1 from samples containing little or no HSA or BSA was bound by the 'alternative' mechanism. Washing of jacalin-Sepharose columns with excess BSA could disrupt the 'alternative' binding and subsequent washing with 0.8 M D-galactose in 0.5 M NaCl/PBS was sufficient to elute all IgA1. The 'alternative' binding to jacalin is probably not restricted to the above-mentioned proteins. Purification of IgA1 by precipitation with jacalin and subsequent gel filtration of the D-galactose-dissolved precipitate was not practical, since jacalin-IgA1 precipitates did not dissolve completely and new complexes were formed during the gel filtration procedure.

Activation of complement by human serum IgA, secretory IgA and IgA1 fragments

Activation of the complement (C) system by human IgA was studied. Both subclasses of IgA, IgA1 and IgA2, and secretory IgA were shown to activate C, as determined by deposition of C3 on glutaraldehyde-activated microwells coated with IgA. The activation of the C system occurred in the presence of MgEGTA and not in D-deficient serum. In addition to C3, deposition of properdin (P) but not of C4 was detected. These results indicate that C activation, as determined by measuring deposition of C3 and P, occurred by the alternative pathway (AP). The data further show that the major part of the hinge region, which is deleted in IgA2 as compared with IgA1 and which forms the major structural difference between the two subclasses, is not involved in C activation. Reduction and alkylation destroyed the ability of IgA to activate C, as has also been demonstrated for IgG. In order to define the C activating region of the IgA molecule, several fragments of IgA1 were tested. The four-chain molecules F(ab')2 and F(abc)2 were shown to activate the AP. No activation was observed with the two-chain fragments Fab and Fc. The Fc fragment of IgA also did not activate the CP, as does the Fc fragment of IgG. This indicates that activation of the AP of C by IgA is dependent on the presence of the F(ab')2 fragment.

IN CONCLUSION

human IgA does activate C by the AP. This activation requires an intact F(ab')2 fragment.

IgA nephropathy is not induced in mice by oral administration of TNP-conjugated ovalbumin

An IgA nephropathy model based on long-term oral administration of protein antigens was evaluated in three mouse strains using trinitrophenyl (TNP)-conjugated ovalbumin. Administration of the antigen for 14 weeks did not induce a significant IgA response nor deposition of IgA in the mesangium in any of the mouse strains. If, however, serum IgA anti-TNP antibodies were induced by intraperitoneal injection of anti-TNP producing MOPC-315 tumor cells, subsequent intravenous injection of antigen resulted in the deposition of IgA immune complexes in the mouse kidneys. Hematuria did not occur. In conclusion, previous data showing that long-term oral administration of protein antigens induces mesangial IgA deposits could not be confirmed with TNP ovalbumin. However, mesangial IgA deposits were obtained in animals treated with MOPC-315 tumor cells as described by Rifai et al. [J. exp. Med. 150: 1161-1173, 1979].

Production and characterization of pepsin fragments of human IgA1 to determine domain-specificity of monoclonal anti-IgA antibodies

Eight human IgA1 myeloma proteins were analysed by SDS-PAGE. These experiments showed that purified IgA1 proteins comprise both fully S-S bonded and partly S-S bonded molecules. Pepsin digestion of the IgA1 proteins yielded three four-chain and two two-chain fragments. The four-chain fragments are likely to be derived from intact IgA through cleavage of its alpha chains at different sites: between the CH2 and CH3 domains or in the hinge region. The occurrence of F(abc) (ab') fragments, with alpha chains of different lengths, showed that the alpha chains of IgA can be cleaved independently at the hinge region site. The two-chain pepsin fragments must originate from IgA molecules, which lack inter-assay-chain disulphide linkages. The fragments F(abc)2 and Fabc tended to form dimers, probably through non-covalent interactions of their CH2 domains. An immunoblotting method was used to identify Fd-, CH2- and CH3-specific anti-IgA antibodies. The CH2-specific antibodies could be subdivided into antibodies recognizing an isotype present on both four-chain and two-chain molecules or on two-chain molecules only.

Monoclonal antibodies against different domains of human IgA: specificities determined by immunoblotting and haemagglutination-inhibition

The specificity of 14 monoclonal antibodies has been determined by immunoblotting (IB) and haemagglutination-inhibition (HAI) analysis using IgA1 and IgA2 myeloma proteins and eight different IgA1 fragments. Two antibodies probably recognized epitopes on the CH1 domain of IgA. They reacted with all Fab-containing fragments irrespective of whether these originated from the same or different IgA proteins. Seven antibodies were directed against epitopes on the CH2 domain. These antibodies were reactive with F(abc)2 fragments. They failed to react with Fab, Fab' and F(ab')2 fragments. Two out of these seven antibodies did not react with two-chain IgA half-molecules and Fabc fragments containing a single heavy and a single light chain. This suggests that these two antibodies recognized an epitope whose structure is dependent on disulfide linked heavy chains. Five other antibodies showed specificity for the CH3 domain. They were reactive with all CH3-containing molecules, irrespective of whether they comprised one or two alpha chains. Our study demonstrates that IB is an appropriate technique to determine domain specificity of monoclonal anti-immunoglobulin reagents. Although the IB tests were performed on denatured proteins the results agreed surprisingly well with those of the HAI analyses. Moreover, the IB technique could be used on fragments which could not be purified well enough for HAI analyses.

Binding of human IgA fragments to protein A-Sepharose studied with an ELISA method

An enzyme-linked immunosorbent assay method was developed to investigate the binding of IgA fragments to protein A. The method proved to be specific and highly sensitive. Contamination with IgG did not interfere with the detection of IgA binding to protein A, and less than 10 ng of IgA could be detected. Four of nine IgA proteins tested bound to protein A to different extents. The binding was not disturbed by reduction and alkylation of the IgA proteins. Four-chain F(abc)2 and F(ab')2 fragments of the protein A-reactive IgA proteins also bound to protein A. On reduction and alkylation these fragments formed two-chain Fabc and Fab' fragments. Of these, Fabc did not bind, whereas both Fab' and IgA1-protease-produced Fab fragments did bind to protein A. These results demonstrate that the Fab fragment has a binding site for protein A. It is suggested that the protein A binding site is located on the CH1 domain of the IgA1 molecule. On Fabc fragments this binding site may be blocked because of structural alterations.

Distribution of antigenic determinants on human IgA1

The distribution of antigenic determinants on human IgA was studied with fragments and mutants of IgA1. F(abc)2 and Fabc, lacking the CH3 domain, F(ab')2 and Fab', lacking the CH2 and CH3 domain, Fab that further lacks most of the hinge region, and Fc fragments were included in our investigations. Antibodies specific for the CH3 domain of IgA1 were found in antisera raised against an alpha 1-HCD protein and in anti-Fc alpha antisera. The antisera detected different antigenic determinants on CH3 as was shown by inhibition with sera from nonhuman primates. An anti-Fc5 mu antiserum detected a determinant on Fc common to IgA and IgM. The serum of an IgA-deficient individual reacted with a determinant on CH2 of four-chain molecules only. A subclass-specific anti-Fabc antiserum detected a determinant which needed interaction of CH2 and CH1 or the hinge region. Anti-Fab antisera reacted with class or subclass specific determinants on CH1. The isoallotype nA2m(2) is probably located on CH1. Its expression requires two alpha-chains stabilized in a conformation attributed to by CH2.

Cleavage of protein A-binding IgA1 with IgA1 protease from Streptococcus sanguis

Protein A-binding fractions of two IgA1 myeloma proteins failed to produce Fc fragments on digestion with IgA1 protease from Streptococcus sanguis. A polymeric protein A-binding IgA1 fraction yielded a protein A-non-binding monomer, which was further cleaved into Fab fragments but it did not yield Fc fragments. The protein A-binding fraction of a monomeric IgA1 yielded an IgA molecule lacking one Fab fragment. Subsequently, the remaining part of its cleaved alpha chain was degraded. Further digestion yielded Fab but not Fc fragments. Similarly, F(abc)2 and Fabc fragments, which lack the CH3 domain (8), yielded Fab fragments but not CH2 domains. Thus, the enzyme in addition to cleaving IgA in the hinge region, under certain conditions, also degrades its Fc fragments.

Allotypic and isotypic aspects of human immunoglobulin A

The location of isotypic, isoallotypic and allotypic determinants is reviewed in the light of data obtained when specific antisera are tested with proteolytic fragments of IgA molecules or mutants of IgA obtained from patients with alpha-heavy chain disease. Isotypic determinants are distributed throughout the alpha chain constant regions although when intact IgA proteins are used as immunogens the CH3 domain is immunodominant. Alpha 1 subclass specific isotypic determinants are present in both Fab and Fc fragments. Amino acid sequence analysis suggest that alpha 1 subclass isotypic determinants depend on substitution in the CH1, hinge and/or CH2 domain. The isoallotypic determinants nA2m(2) appears to be located on the CH1 domain and appears to require disulphide-linked alpha chains for its expression. The allotypic determinant A2m(2) appears to be located in the CH3 domain involving residues 428, 458 and/or 467. The latter residues are present in both A2m(1) and A1 proteins which indicates that for A2m(1) to be the antithetical determinant of A2m(2), the determinant formed by residues 428, 458 and/or 467 in these proteins must be influenced by subclass differences which allows its expression in A2m(1) proteins and not in A1 proteins.

Production and characterization of antibodies specific for domains of human IgM

A method of preparing antibodies against c mu 3 and c mu 4 domains of human IgM is described. c mu 3- and c mu 4-binding antibody fractions were isolated by affinity chromatography from IgG fractions of antisera raised against Fc5 mu and Fc mu' fragments. c mu 3 and c mu 4 fragments had been prepared from human IgM kappa (Key) by hot trypsin digestion. Haemagglutination inhibition tests showed that the c mu 4-binding fraction only reacted with c mu 4 fragments. The c mu 3-binding fraction reacted with c mu 3 fragments but showed a minor reaction with c mu 4 fragments. Immunization with Fc mu' fragments predominantly yielded antibodies against the c mu 3 domain, whereas immunization with Fc5 mu fragments yielded antibodies more directed against the c mu 4 domain. Immunization with isolated c mu 4 fragments led to the production of antibodies which reacted with the isolated c mu 4 domain but not with the c mu 4 domain within the larger structures of Fc mu' or Fc5 mu fragments.

IgA1 half molecules in human multiple myeloma and the in vitro production of similar fragments from intact IgA1 molecules

This paper describes an IgA related protein Vla which occurred in the serum and urine of a patient with multiple myeloma. The protein was isolated from urine; it had a molecular mass of 70,000 daltons. It was shown to be a two chain IgA half molecule, consisting of a deleted alpha heavy chain, with a molecular mass of 42,000 daltons, which was disulphide linked to a normal kappa type light chain. Fabc fragments were produced from an unrelated myeloma IgA. These had the same biochemical properties as protein V1a, except for the absence of the disulphide linkage between the deleted heavy chains and the light chains. Protein Vla and the Fabc fragments could both be cleaved by IgA1 protease from Streptococcus sanguis, which indicates the presence of the alpha 1 hinge region. An inventory of its antigenic determinants and their similarity to those of previously characterized F(abc)2 fragments, indicates that protein Vla, like the Fabc fragments, contains the CH1 and CH2 domains, but lacks most of the CH3 domain. The fact that cleavage by IgA1 protease from S. sanguis yields a Fab fragment but fails to yield a CH2 domain demonstrates that cleavage by the enzyme is not only restricted to the Pro227-Thr228 bond in the IgA1 hinge region.

Binding of human IgA myeloma proteins to protein A. Evidence for different binding mechanisms

The binding of fifteen IgA myeloma proteins to protein A was studied using affinity chromatography on protein A-Sepharose CL-4B. The percentage to which the proteins bound was variable from 1% to 11% with the exception of IgA(GED) with a binding capacity of 22%, and IgA(KLO) with a binding capacity of 84%. The binding of the proteins IgA(GED) and IgA(KLO) was studied further. IgA(GED) was a monomer, Iga(KLO) a polymer. The characteristics of the binding of these proteins were different. The protein A-reactive fraction of IgA(KLO), but not of IgA(GED) remained fully reactive on repeated protein A chromatography. Furthermore, the binding of IgA(GED) could be reduced to about 3% by either a decrease in pH to 4.5 or an increase in NaCl concentration to 2.0M, whereas the binding of IgA(KLO) was similarly reduced by a decrease in pH but its binding only reduced to half of the original value on a similar increase of NaCl concentration. In addition, F(ab')2 fragments of IgA(KLO), but not of IgA(GED), bind to protein A-Sepharose CL-4B, whereas IgA1 protease-produced Fab fragments of neither of the proteins did so, nor did pepsin-produced Fab' fragments. This suggests that the binding of F(ab')2 fragments of IgA(KLO) needs an intact hinge region.