Are antibodies to carbonic anhydrase II specific for anti-mitochondrial antibody-negative primary biliary cirrhosis?

Antibodies to carbonic anhydrase II (CAII) have been reported to be specific to anti-mitochondrial antibody (AMA)-negative primary biliary cirrhosis (PBC). We examined whether antibodies to CAII are specific for AMA-negative PBC or a nonspecific response in autoimmune liver disease. Antibody assays to CAII, by western immunoblot (dilution 1:200), were performed on sera from 16 AMA-negative PBC patients, 21 AMA-positive PBC patients, 21 autoimmune hepatitis type 1 (AIH) patients, and 18 alcoholic liver disease (ALD) patients. CAII antibody activity was found in 8 of 16 (50%) of the AMA-negative PBC patients, 9 of 21 (43%) of the AMA-positive PBC group, 10 of 21 (48%) of the AIH group, and in 3 of 18 (17%) of the ALD control group. There was no difference in the prevalence of CAII antibody reactivity between the AMA-negative PBC, AMA-positive PBC, and AIH groups. In conclusion, we determined that CAII antibodies are detected with equal frequency in AMA-positive PBC and AIH. Given that CAII antibodies have been reported in other nonhepatic autoimmune diseases, we conclude that CAII antibodies are likely a nonspecific marker of autoimmunity rather than specific for AMA-negative PBC.

Clinical analysis of autoimmune-related pancreatitis

OBJECTIVE

Several investigators have reported on autoimmune-related pancreatitis, but the clinical findings and pathophysiology still remain unclear. To clarify it, we analyzed eight patients with autoimmune pancreatitis.

METHODS

We evaluated clinical findings in eight patients (four men and four women) with autoimmune-related pancreatitis. Patients were aged 45-73 yr (mean, 57.5 yr). We examined blood chemistry and immunological studies, including autoantibodies against lactoferrin or carbonic anhydrase II, and compared ERCP images with clinical findings. In two patients, we studied the subset of lymphocytes infiltrating in the pancreas by immunohistochemistry and flow cytometry.

RESULTS

Four of eight patients had jaundice, two had renal dysfunction, two had abdominal pain, and two had back pain. Three patients were complicated with other autoimmune diseases. Three patients showed abnormal pancreatic exocrine function by an N-benzoyl-L-tyrosyl-para-aminobenzoic acid excretion test. Antinuclear antibody was detected in four of eight patients, antilactoferrin antibody in three of six, anticarbonic anhydrase II antibody in two of six, antismooth muscle antibody in two of seven, and rheumatoid factor in one of eight. All eight patients showed segmental stenosis of the main pancreatic duct by ERCP. Four patients showed stenosis of the common bile duct as well as the pancreatic duct. Microscopic findings showed infiltration of CD4-positive lymphocytes around the pancreatic duct, and HLA-DR was expressed on both CD4-positive cells and pancreatic duct cells. In two patients, stenosis of the pancreatic duct improved by prednisolone.

CONCLUSIONS

Autoimmune mechanism may be involved in some patients with idiopathic pancreatitis associated with hypergammaglobulinemia.

Immunolocalization of CA II and H+ V-ATPase in epithelial cells of the mouse and rat epididymis

Acidification of the epididymal lumen has been suggested to play an important role in sperm functions; however, the cell types, pumps, and mechanisms involved have not been fully addressed. In this study, carbonic anhydrase II (CA II) and a 67-kd subunit of Neurospora crassa vacuolar proton adenosinetriphosphatase (H+ V-ATPase) pump were immunolocalized using light microscopy and electron microscopy (EM) in the epididymis of rats and mice. In both animals, narrow cells, identified in the initial segment and intermediate zone of the epididymis, contained numerous small vesicles in their apical region, often cup-shaped in appearance. In the mouse but not rat, these cells also possessed numerous cisternae of smooth endoplasmic reticulum, suggesting steroid synthesis; and cytoplasmic blebs of their apical cell surface, which appeared to detach, suggesting apocrine secretion. Anti-CA II antibody was immunocytochemically localized in the light microscope within narrow cells but not over any other cell types of the entire epididymis. Anti-H+ V-ATPase antibody was also localized in narrow cells of the initial segment and intermediate zone; as well as clear cells of the caput, corpus, and cauda regions. Using EM, gold particles for anti-CA II and H+ V-ATPase antibodies were noted in the apical region of narrow cells in relation to the numerous, small, cup-shaped vesicles. Although CA II was mainly located in the cytosol near these vesicles, H+ V-ATPase appeared on their delimiting membrane and on the apical plasma membrane of these cells. A similar distribution was noted for H+ V-ATPase in clear cells. The nature of the small vesicles of the apical region of narrow cells was examined with electron-dense fluid phase tracers that were introduced into the epididymal lumen. The tracers appeared within these vesicles and a few endosomes 1 hour after injection, suggesting that they contact the apical plasma membrane. Since these vesicles are also related to CA II and H+ V-ATPase, the data suggests that, as the site of proton production, the vesicles recycle to and from the apical cell surface, and in this way, deliver protons to the epididymal lumen for acidification. Clear cells and their expression of H+ V-ATPase may also serve in this function. In summary, both narrow and clear cells appear to be involved in luminal acidification, an activity that may be essential for sperm as they traverse and are stored in the epididymis.

[Antiretinal antibodies associated with cystoid macular edema]

AIM

Recently, anti-Enolase and anti-carbonic anhydrase antibodies have been observed in over 60% of patients with retinitis pigmentosa (RP) and cystoid macular oedema (CME). We investigated the presence of these antibodies in a series of patients with CME due to different pathologies.

METHODS

In 10 patients with CME serum antibodies against Carbonic anhydrase (CA) II (30 kD) and Enolase (46 kD) were sought using Western Blots, Dot Blots as well as ELISA.

RESULTS

Western and dot blotting showed anti-CA II antibodies in all and anti-Enolase antibodies in six of the 10 patients. The average titer measured with ELISA was 0.9 +/- 0.08 OD Units (0.35-1.4) with a dilution of 1:400.

CONCLUSION

The presence of anti-retinal antibodies in the serum of all patients confirms the high prevalence of these antibodies in patients with CME. This may suggest that a dysfunction of CA and enolase activity in the retinal pigment epithelium may lie at the root of oedema formation, whereas other mechanisms may be responsible in the absence of these antibodies.

Elevated serum levels of antibodies to carbonic anhydrase I and II in patients with chronic pancreatitis

An immune-mediated reaction to pancreatic structures has been postulated for the pathogenesis of chronic pancreatitis (CP). Several reports demonstrate the presence of antibodies to the pancreatic ductal epithelium in some patients suffering from CP. Serum antibodies to carbonic anhydrase I (anti-CA I) and II (anti-CA II) are present in patients affected by idiopathic CP. The aim of this study was to evaluate the presence of anti-CA I and anti-CA II in a series of patients with CP. We studied 78 consecutive CP patients (62 male, 16 female; mean age 48.6 +/- 10.2 years) referred to the Verona University Center for the Study of the Pancreas. As a control group, we studied 26 healthy subjects recruited from among the medical and nursing staff of the center. Serum anti-CA I and anti-CA II levels were quantified by enzyme-linked immunosorbent assay using a standard method with minor modifications. The mean absorbance of antibodies was higher in CP patients than in control subjects (anti-CA I: 0.064 +/- 0.042 vs. 0.047 +/- 0.015, p = 0.051; and anti-CA II: 0.038 +/- 0.02 vs. 0.029 +/- 0.014, p = 0.033). Positive results were arbitrarily defined as absorbance values >0.067 for anti-CA I and 0.047 for anti-CA II. We found anti-CA I and anti-CA II positivity in 21 of 78 (27%) and 20 of 78 (26%) of CP patients, respectively, and in only two of 26 control subjects (7.7%) (p = 0.032 and 0.039). Twenty-two of 26 subjects in the control group (84.6%) and 48 of 78 patients (61.5%) in the CP group tested negative for both antibodies (p = 0.03). None of the control subjects and 12 of 78 (16.6%) of the CP patients tested positive for both anti-CA I and anti-CA II. We observed a significant correlation between anti-CA I and anti-CA II serum levels in control subjects (R = 0.423; p = 0.016) and in CP patients (R = 0.584; p < 0.0001). No correlation was found between serum antibody levels and any of the following variables: length of disease, alcohol consumption, smoking habits, pancreatic surgery, pancreatic calcifications, diabetes, and steatorrhea. Serum levels of anti-CA I and anti-CA II are elevated in some patients suffering from CP.

Immunochemical evidence for a unique GPI-anchored carbonic anhydrase isozyme in human cardiomyocytes

To clarify the controversial question of cell-specific distribution of carbonic anhydrase (CA) in the heart, endothelial cells and cardiomyocytes were isolated from porcine and human hearts and were characterized with cell-specific markers. CA activity was found in the microsomal fraction of both cell types. It was shown by Triton X-114 phase separation that both cell types possess a membrane-bound form of CA. These CAs share the same mechanism of membrane-anchoring via glycosylphosphatidylinositol (GPI), which excludes identity with transmembrane isoforms CA IX or CA XII. Western blotting analysis of human microsomes with anti-human CA IV antibodies revealed a marked difference in immunoreactivity. Endothelial CA activity resulted in 11-fold stronger CA IV bands compared with identical amounts of myocytic CA activity, indicating that cardiac endothelium and cardiomyocytes possess immunologically distinct forms of CA. We conclude that in human hearts CA IV is associated with the endothelium, whereas most of the CA in myocytes is not identical with one of the known CA isozymes. This suggests that cardiomyocytic CA is a novel isozyme.

Autoimmune-related pancreatitis is associated with autoantibodies and a Th1/Th2-type cellular immune response

BACKGROUND & AIMS

Although autoimmunity may be involved in some cases of pancreatitis, the mechanism is still unknown. To clarify this, we studied serum autoantibodies, subsets of lymphocytes, and the Th1/Th2 balance of cellular immune responses in patients with autoimmune-related pancreatitis (AIP).

METHODS

Seventeen patients with AIP (8 men and 9 women; age, 53.2 +/- 13.0 years) were studied. Autoantibodies including antilactoferrin (ALF) or carbonic anhydrase II antibody (ACA-II) were examined using the enzyme-linked immunosorbent assay (ELISA) or the indirect fluorescein antibody method. Intracellular cytokines (interferon gamma and interleukin 4) and subtypes of peripheral blood lymphocytes were examined by flow cytometry and ELISA.

RESULTS

More than one autoantibody was observed in all 17 patients. Serum antinuclear antibody was detected in 13 of 17 patients, ALF antibody in 13, ACA-II antibody in 10, rheumatoid factor in 5, and anti-smooth muscle antibody in 3, but antimitochondrial antibody in none. The serum levels of ACA-II and LF antibody were not correlated. HLA-DR(+)CD8(+) and HLA-DR(+)CD4(+) cells were significantly increased in peripheral blood (P < 0.05). CD4(+) cells producing interferon gamma and the secreted levels were significantly increased compared with those in controls (P < 0.05), but interleukin 4 was not increased.

CONCLUSIONS

An autoimmune mechanism against CA-II or LF, and Th1-type immune response, may be involved in AIP.

Identification of carbonic anhydrase XII as the membrane isozyme expressed in the normal human endometrial epithelium

Although previous studies demonstrated carbonic anhydrase (CA) activity in the human endometrium, the CA isozyme(s) responsible for this activity has not been established. In this report, we provide the first evidence that the CA isozyme XII, a recently identified transmembrane isozyme that is expressed in normal kidney and greatly overexpressed in some renal cancers, is present in endometrium. We show by immunohistochemistry that CA XII is expressed in the basolateral plasma membrane of epithelial cells of normal human endometrium. Expression of CA XII in uterus was confirmed by Northern blotting. Detergent-solubilized CA XII was isolated from human endometrium by inhibitor affinity chromatography and characterized by isoelectric focusing and Western blot as a polypeptide with a pI of 6.3. The high expression of CA XII in the endometrial epithelium suggests that it may be functionally linked to the pH-dependent events in spermatozoa that precede fertilization. Its basolateral location and extracellular active site could also allow it to influence the morphological changes in endometrium that occur during the menstrual cycle.

A study of anti-carbonic anhydrase II antibodies in rheumatic autoimmune diseases

Autoantibodies to human carbonic anhydrase II (CAII) were screened by ELISA in 109 sera from Asian Japanese patients with systemic lupus erythematosus (SLE), primary Sjögren's syndrome (Sjs), progressive systemic sclerosis (PSS) and dermatomyositis (DM). Anti-CAII antibodies were positive in 24.1% of SLE, 20.0% of primary Sjs, 16.7% of PSS and 25.0% of DM. On the other hand, sera from atopic dermatitis, bullous pemphigoid and psoriasis patients showed no activity for anti-CAII antibodies. CAII could be a common exonuclear autoantigen in subsets of rheumatic autoimmune diseases.

Autoimmune cholangiopathy

Currently available evidence is insufficient to classify PBC and AIC as separate diseases. The ultimate answer to the question of whether AIC, defined as AMA-negative PBC with ANA or SMA, is a disease distinct from AMA-positive PBC with or without ANA will require a detailed comparison of etiologic factors and pathogenetic mechanisms, once they are elucidated. It is intriguing to consider the suggestion of Heathcote that the term autoimmune cholangitis be adopted to describe PBC with or without detectable AMA. However, it is improbable that the venerable term PBC will be supplanted. Hepatologists will probably continue to use the terms AIC and AMA-negative PBC interchangeably, with little risk of being misunderstood.

The ability of anti-carbonic anhydrase II antibody to distinguish autoimmune cholangitis from primary biliary cirrhosis in Japanese patients

Serum antibody against carbonic anhydrase (CA) II has been described as a serological marker for distinguishing autoimmune cholangitis (AIC) from primary biliary cirrhosis (PBC). To validate this finding in a Japanese population, we evaluated sera from patients with PBC and AIC for antibody to human CA II. An enzyme-linked immunosorbent assay was employed to quantify serum antibody against CA II in patients with PBC (n = 40), AIC (n = 23), autoimmune hepatitis (n = 10), and extrahepatic obstructive jaundice (n = 10). Compared with the finding of a 4% prevalence of anti-CAII antibody in healthy subjects (n = 24), a significantly higher prevalence of anti-CA II antibody was detected in patients with PBC (35%) and AIC (30%) (P < 0.05), but not in patients with autoimmune hepatitis and patients with obstructive jaundice. No significant difference was observed between PBC and AIC patients. These results showed that AIC and PBC would be indistinguishable by anti-CA II antibody testing in Japanese patients. However, the finding of serum anti-CA II antibody in patients with PBC and AIC supports the disease concept of autoimmune exocrinopathy.

Production and characterization of monoclonal antibodies to human carbonic anhydrase III

Carbonic anhydrase III (CAIII) is a cytosolic protein found almost exclusively in slow-oxidative skeletal muscle fibers. Upon excessive skeletal muscle activity or damage, CAIII is rapidly released into serum. CAIII is not found in cardiac muscle, whereas the muscle protein myoglobin (Myo) is found in skeletal and cardiac muscle. Because CAIII and Myo are released from injured muscle in a constant ratio, an increase in the Myo/CAIII ratio may be useful as an early diagnostic indicator of acute myocardial damage. Although several reliable Myo immunoassays have been established, no similar CAIII immunoassay is commercially available. We produced murine monoclonal antibodies (MAbs) to human CAIII using standard immunization and cell fusion procedures. Using an enzyme-linked immunoadsorbent assay (ELISA), three MAbs showed strong immunoreactivity with CAIII, but low to moderate levels of cross-reactivity with closely related isoenzymes CAI and CAII. The three MAbs demonstrated unique patterns of reactivity toward CAI, CAII, and CAIII, suggesting that different CAIII epitopes are recognized by the three MAbs. Specificity was further examined by Western blot analysis. These MAbs demonstrated potential for use in the development of an immunoassay for CAIII, and for investigating the biology of skeletal muscle injury in vivo.

Antibody to carbonic anhydrase II is present in primary biliary cirrhosis (PBC) irrespective of antimitochondrial antibody status

Antibody to carbonic anhydrase II, an enzyme abundantly present in biliary epithelium, has been proposed as a diagnostic marker for antimitochondrial antibody-negative PBC. In this study we determine its prevalence and clinical significance in a large series of patients with antimitochondrial antibody-positive and -negative PBC. Reactivity to carbonic anhydrase II was sought by Western immunoblotting in sera from 215 consecutive patients with PBC (26 antimitochondrial antibody-negative), 13 with autoimmune hepatitis, 25 with primary Sjögren's syndrome (pSS), 12 with systemic sclerosis, 19 with systemic lupus erythematosus and 73 healthy subjects. The prevalence of antibody to carbonic anhydrase II (titre 1:100) in PBC was 8%. No specific reactivity to carbonic anhydrase II was found in antimitochondrial antibody-negative PBC (7% versus 8% in antimitochondrial antibody-positive PBC). Ascites (P = 0.006) and Sjögren's syndrome (SS) (P = 0.022) in PBC were significantly associated with presence of the antibody. In patients with SS associated with PBC, the prevalence (19%) was similar to that observed in pSS (16%). At a serum dilution of 1:40, the prevalence of positive sera in PBC rose to 27% but disease specificity was reduced. Our findings in a large population of PBC patients rule out a relation between presence of antibody to carbonic anhydrase II and lack of antimitochondrial antibody. The higher prevalence of ascites found in positive patients warrants further evaluation.

Isolation and characterization of 26- and 30-kDa rat liver proteins immunoreactive to anti-sterol carrier protein-2 antibodies

Although the existing literature suggests that the sterol carrier protein-2 (SCP-2) gene has only two initiation sites encoding for a 58- and a 15-kDa protein, respectively, this does not explain the profusion of other putative SCP-2-related proteins detectable on Western blotting. Two of these additional anti-SCP-2 immunoreactive proteins, 13.2 and 46 kDa, appear due to proteolytic processing of the two gene transcripts. However, the origin of additional immunoreactive rat liver proteins near 26 and 30 kDa is unclear. The latter proteins were consistently detected on Western blotting by three independent types of polyclonal antisera: anti-13.2-kDa SCP-2, anti-synthetic peptide from the amino-terminus of the 13.2-kDa SCP-2, and Protein A affinity-purified anti-synthetic peptide to the amino-terminus of 13.2-kDa SCP-2. To resolve whether the 26- and 30-kDa proteins are SCP-2 gene products, each protein was isolated from rat liver and purified to homogeneity as indicated by Tricine-SDS polyacrylamide gel electrophoresis, isoelectric focusing, and/or mass spectroscopy. Their masses, determined by MALDI-TOF mass spectroscopy, were 25.7 and 29.8 kDa, respectively. However, the mass spectral data were not consistent with either protein being an SCP-2 gene product. Peptide mass mapping of the 25.7-kDa protein revealed identity to the rat 25,784.79-Da glutathione-S-transferase. Furthermore, neither the mass nor the amino acid composition of the 29.8-kDa protein correlated with any SCP-2 gene product or dimerized SCP-2 gene product. A database search of the amino acid composition identified the protein as rat carbonic anhydrase. In summary, although the 26- and 29.8-kDa proteins may share some common epitopes with the 13.2-kDa SCP-2, they were not SCP-2 gene products.

Potent enzyme inhibitors derived from dromedary heavy-chain antibodies

Evidence is provided that dromedary heavy-chain antibodies, in vivo-matured in the absence of light chains, are a unique source of inhibitory antibodies. After immunization of a dromedary with bovine erythrocyte carbonic anhydrase and porcine pancreatic alpha-amylase, it was demonstrated that a considerable amount of heavy-chain antibodies, acting as true competitive inhibitors, circulate in the bloodstream. In contrast, the conventional antibodies apparently do not interact with the enzyme's active site. Next we illustrated that peripheral blood lymphocytes are suitable for one-step cloning of the variable domain fragments in a phage-display vector. By bio-panning, several antigen-specific single-domain fragments are readily isolated for both enzymes. In addition we show that among those isolated fragments active site binders are well represented. When produced as recombinant protein in Escherichia coli, these active site binders appear to be potent enzyme inhibitors when tested in chromogenic assays. The low complexity of the antigen-binding site of these single-domain antibodies composed of only three loops could be valuable for designing smaller synthetic inhibitors.

Human carbonic anhydrase XII: cDNA cloning, expression, and chromosomal localization of a carbonic anhydrase gene that is overexpressed in some renal cell cancers

We report the cloning and characterization of a tumor-associated carbonic anhydrase (CA) that was identified in a human renal cell carcinoma (RCC) by serological expression screening with autologous antibodies. The cDNA sequence predicts a 354-amino acid polypeptide with a molecular mass of 39,448 Da that has features of a type I membrane protein. The predicted sequence includes a 29-amino acid signal sequence, a 261-amino acid CA domain, an additional short extracellular segment, a 26-amino acid hydrophobic transmembrane domain, and a hydrophilic C-terminal cytoplasmic tail of 29 amino acids that contains two potential phosphorylation sites. The extracellular CA domain shows 30-42% homology with known human CAs, contains all three Zn-binding histidine residues found in active CAs, and contains two potential sites for asparagine glycosylation. When expressed in COS cells, the cDNA produced a 43- to 44-kDa protein in membranes that had around one-sixth the CA activity of membranes from COS cells transfected with the same vector expressing bovine CA IV. We have designated this human protein CA XII. Northern blot analysis of normal tissues demonstrated a 4.5-kb transcript only in kidney and intestine. However, in 10% of patients with RCC, the CA XII transcript was expressed at much higher levels in the RCC than in surrounding normal kidney tissue. The CA XII gene was mapped by using fluorescence in situ hybridization to 15q22. CA XII is the second catalytically active membrane CA reported to be overexpressed in certain cancers. Its relationship to oncogenesis and its potential as a clinically useful tumor marker clearly merit further investigation.

Different susceptibility of mice to immune-mediated cholangitis induced by immunization with carbonic anhydrase II

Carbonic anhydrase II (CA-II), an enzyme that catalyzes hydration of carbon dioxide to bicarbonate and hydrogen ions, is located exclusively in cholangiocytes in the liver. Recently, patients with autoimmune cholangitis have been reported to have serum antibodies to CA-II. Moreover, active immunization of susceptible mice with CA-II results in inflammation of submandibular glands, where CA-II is also expressed. In the present study, we attempted to produce cholangitis by immunization with CA-II using two strains of mice with different potential susceptibilities. Balb/c and DBA/1J mice were immunized with a dose of human CA-II (100 microg) intraperitoneally every other week on three occasions. One week after the final immunization, mice were killed and blood and tissue samples harvested. Light and electron microscopic evaluation for inflammation was performed under coded identification. After immunization of Balb/c mice, numerous mononuclear cells, mostly CD4-positive T cells, appeared around bile ducts; lymphocyte invasion between cholangiocytes was also seen. Inflammation was not observed outside the liver. Morphologic evidence of cholangitis was observed in 8 (53.3%) of 15 Balb/c mice and in 3 (20%) of 15 DBA/1 J mice. In the control mice immunized with bovine serum albumin (BSA), cholangitis was observed in only 1 (6.7%) of 15 Balb/c mice and none of 15 DBA/1J mice. Balb/c mice immunized with CA-II had statistically significant cholangitis compared with those immunized with BSA (p < 0.01), whereas DBA/1J did not show a significant difference from controls. Balb/c mice immunized with CA-II showed specific antibody production after immunization, whereas DBA/1J mice immunized with CA-II had anti-CA-II antibody even in preimmune sera. Adoptive transfer of splenocytes from CA-II-immunized Balb/c mice resulted in cholangitis in two (66.7%) of three Balb/c recipients. These data strongly suggest that the cholangitis can be induced by CA-II immunization in susceptible strains of mice.

Autoimmune pancreatitis: CT and MR characteristics

OBJECTIVE

Our goal was to elucidate the CT and MR imaging characteristics in patients with autoimmune pancreatitis, which is a reversible chronic pancreatitis with an autoimmune cause.

CONCLUSION

On CT and MR imaging, a capsulelike rim, which is thought to correspond to an inflammatory process involving peripancreatic tissues, appears to be a characteristic finding of autoimmune pancreatitis. Also, diffuse pancreatic enlargement along with hypointensity on T1-weighted MR images and delayed enhancement on dynamic CT and MR studies are other features of this disorder.

Autoimmune pancreatitis as a new clinical entity. Three cases of autoimmune pancreatitis with effective steroid therapy

The most common forms of chronic pancreatitis are related to alcohol ingestion, whereas the entity of non-alcohol-associated (idiopathic) pancreatitis is poorly understood. Autoimmunity has been suggested as a possible etiologic factor of idiopathic chronic pancreatitis. A total of 362 Japanese patients underwent endoscopic retrograde pancreatography (ERP) for suspected pancreatic disease, and 161 were diagnosed with chronic pancreatitis. Among them, we found three cases (1.86% incidence) of unique chronic pancreatitis, in which ERP revealed diffuse narrowing of the main pancreatic duct with an irregular wall. We diagnosed these three patients as having pancreatitis associated with an autoimmune mechanism morphologically and biochemically and started them on steroid therapy. The characteristics of the these three patients were as follows: hypergammaglobulinemia, eosinophilia, ultrasonography showing hypoehoic diffuse swelling in the pancreas (sausage-like appearance), ERP showing diffuse narrowing of the main pancreatic duct with irregular like thumbprint-like marks, reversible exocrine insufficiency, and positive anti-carbonic anhydrase II antibody. After one month of the treatment with steroids, pancreatitis dramatically improved morphologically and enzymatically. Here we describe these cases of the suspected autoimmune chronic pancreatitis. We must recognize the concept and the features of autoimmune pancreatitis in order to avoid unnecessary surgery as pancreatic cancer.

Identification and characterization of a gene encoding a vertebrate-type carbonic anhydrase in cyanobacteria

A gene (designated ecaA) encoding a vertebrate-like (alpha-type) carbonic anhydrase (CA) has been isolated from two disparate cyanobacteria, Anabaena sp. strain PCC 7120 and Synechococcus sp. strain PCC 7942. The deduced amino acid sequences correspond to proteins of 29 and 26 kDa, respectively, and revealed significant sequence similarity to human CAI and CAII, as well as Chlamydomonas CAHI, including conservation of most active-site residues identified in the animal enzymes. Structural similarities between the animal and cyanobacterial enzymes extend to the levels of antigenicity, as the Anabaena protein cross-reacts with antisera derived against chicken CAII. Expression of the cyanobacterial ecaA is regulated by CO2 concentration and is highest in cells grown at elevated levels of CO2. Immunogold localization using an antibody derived against the ecaA protein indicated an extracellular location. Preliminary analysis of Synechococcus mutants in which ecaA has been inactivated by insertion of a drug resistance cassette suggests that extracellular carbonic anhydrase plays a role in inorganic-carbon accumulation by maintaining equilibrium levels of CO2 and HCO3- in the periplasm.

Antibodies to carbonic anhydrase in endometriosis: prevalence, specificity, and relationship to clinical and laboratory parameters

OBJECTIVE

To investigate the presence and clinical association of serum autoantibodies to carbonic anhydrase (CA) in women with and without endometriosis.

DESIGN

Sera were tested in an ELISA against human and bovine CAI and/or CAII isoenzymes and by Western immunoblotting of trypsin-digested fragments of human CAII as antigens. The ELISA positivity was defined as mean + 2 SD of 100 control sera. Positive sera also were tested for the presence of antiendometrial antibodies and antinuclear antibodies (ANA) by indirect immunofluorescence assays (IFA) on endometrial (ECC) and HEp-2 cells, antibodies to single-stranded (ss) and double-stranded (ds) DNA by the Farr-type RIA and Crithidia IFA, and extractable nuclear antigens (Sm, nRNP, Ro, and La) by an ELISA.

PATIENTS

Sera from 319 patients with laparoscopic diagnosed pelvic endometriosis (100 stage I, 95 stage II, 67 stage III, and 57 stage IV), 100 with other gynecologic disorders, and 100 control women were used.

RESULTS

In the ELISA, 113 of 319 (35.4%) endometriosis sera had elevated immunoglobulin G antibodies against nondenatured CA isoenzymes. The reactivity of sera from the endometriosis group was significantly higher (35%) in all four subgroups of patients than each of the nonendometriosis sera (< 12% and < 6%, respectively). No stage-dependent variation of an autoantibody pattern was evident. However, anti-CA autoantibodies were present in 66.3% of women with endometriosis-associated infertility. The frequency of anti-CA autoantibodies was significantly higher (by 51.7%) in women with antiendometrial antibodies detectable by IFA. In addition, in sera positive for anti-CA antibodies, the frequency of ANA also was increased (20/113 [17.6%]) with titers of 1:40 to 1:1,080. The ANA-positive sera were negative for anti-ssDNA, anti-dsDNA, anti-Sm, anti-nRNP, and anti-La. However, three sera were positive for anti-Ro antibodies. Immunoblotting study of autoantibody reactivity with trypsin-digested subfragments of human CAII revealed consistent immunoreactivity with 14 to 6.2-kd range CAII peptides.

CONCLUSIONS

[1] A subgroup of patients with endometriosis have autoantibodies directed to native and linear epitopes of the CA protein. [2] Prevalence of anti-CA antibodies was associated with antiendometrial antibodies and ANA. [3] Anti-CA antibodies were associated with a higher predictive value of the disease when all patient subgroups were considered together.

Endometriosis: identification by carbonic anhydrase autoantibodies and clinical features

Reliably diagnosing endometriosis traditionally requires surgery. To evaluate a possible non-surgical method, a case-control series of unexplained infertility patients undergoing diagnostic laparoscopy were scored by clinical criteria and reactivity to human carbonic anhydrase II by Western blotting. The CA II autoantibodies were found in none of the fertile controls, 38 percent of infertile controls, 55 percent of stage 1, 50 percent of stage 2, 73 percent of stage 3, and 85 percent of stage 4 endometriosis patients. Advanced endometriosis was associated with more intense reactivity. Combining clinical and antibody scores for infertile groups showed a positive association with disease stage with positive predictive values of 76 to 95 percent, negative predictive values of 90 to 60 percent, and a likelihood ratio of 18.3. It is concluded by us that CA II immunoreactivity, clinical, and combined scores all identified stages 2 to 4 endometriosis patients. However, based on predictive values and likelihood ratios, the combined score is best at identifying endometriosis non-surgically.

Carbonic anhydrase II in microglia in forebrains of neonatal rats

In the brains of adult rodents carbonic anhydrase II (CA) immunoreactivity has been observed in the choroid plexus and in oligodendrocytes, astrocytes, and myelin. Localization and functions of CA in the neonatal brain, however, have been controversial. One issue is whether the CAII-immunopositive round and ameboid cells in the corpus callosum and cingulum in the rat CNS during the first postnatal week are oligodendrocytes or microglia. Colocalization of CAII with the microglial antigen, ED1, and the microglia-specific isolectin, BSI-B4, suggested that most (approx. 60%) of the CAII-positive round and ameboid cells in rat brain during the first postnatal week were, indeed, macrophages and microglia. During that initial week, some CAII-positive protoplasmic astrocytes (approx. 40%) were observed as well. At the end of the first postnatal week smooth-surfaced CAII-positive cells began to appear in the corpus callosum. Those cells also bound MAbO4, a marker for the oligodendrocyte cell line. We conclude that during the first postnatal week most of the CAII-positive cells are macrophages and microglia, and that some are protoplasmic astrocytes. During the second postnatal week CAII-positive cells in the oligodendrocyte lineage become apparent, and by the end of that week there are few CAII-positive microglia. Confocal microscopy suggests that in brains of three-day-old rats the ameboid microglia are associated with nerve fibers, where they may perform phagocytosis of axons, directional guidance of axons, or disinhibition of axonal growth.

Serum antibodies to carbonic anhydrase I and II in patients with idiopathic chronic pancreatitis and Sjögren's syndrome

BACKGROUND & AIMS

Patients with idiopathic chronic pancreatitis and Sjögren's syndrome show immune responses against a 60-kilodalton protein isolated from human pancreas extracts. Monoclonal antibody SP3-1, raised against the 60-kilodalton protein, reacts with ductal cells in several exocrine organs and cross-reacts with human carbonic anhydrase II. The present study evaluated serum from patients with these diseases for antibodies to human carbonic anhydrase I and II.

METHODS

An enzyme-linked immunosorbent assay was used to quantify serum antibody against carbonic anhydrase I and II.

RESULTS

Serum antibodies against carbonic anhydrase I and II were detected in 7 and 11 of 33 patients with idiopathic chronic pancreatitis, respectively, and in 8 and 13 of 21 patients with Sjögren's syndrome, respectively. The positive prevalence rates of patients with antibodies of carbonic anhydrase II were significantly different among patients with idiopathic chronic pancreatitis and Sjögren's syndrome compared with normal patients (1 of 21). There were no significant differences in the prevalence rates of patients with alcoholic chronic pancreatitis (3 of 20), gallstone-related chronic pancreatitis (0 of 7), and primary biliary cirrhosis (1 of 11).

CONCLUSIONS

The results suggest that carbonic anhydrase II is one candidate target antigen recognized during the autoimmune pathophysiology observed in idiopathic chronic pancreatitis and Sjögren's syndrome.

Expression of carbonic anhydrase II mRNA and protein in oligodendrocytes during toxic demyelination in the young adult mouse

The aim of this study was to identify events that might take place in oligodendrocytes early in the process of demyelination, i.e., before the occurrence of massive loss of myelin. It was considered important to focus on demyelination and remyelination in young adults, in whose brains there would be relatively few juvenile glial precursor cells. CAII mRNA and protein were used to monitor changes in oligodendrocytes during cuprizone intoxication in the mice. After four or eight weeks of cuprizone feeding CAII message became less plentiful in oligodendrocyte processes. Two days after removal of cuprizone CAII message had appeared in those cell processes. Four or eight weeks after beginning cuprizone feeding CAII protein had decreased approximately 25% in forebrain homogenates. The loss of CAII protein was reversible after four weeks on cuprizone, but not after eight weeks. After four weeks of cuprizone feeding the numbers of CAII mRNA-positive oligodendrocytes had decreased by approximately 50%, and after eight weeks, by approximately 80%. By 12 weeks, however, the number of oligodendrocytes expressing CAII mRNA had spontaneously returned to normal levels. Before eight weeks of cuprizone feeding, loss of myelinated tracts in the corpus striatum was reversible. Demyelination appeared to become irreversible after nine weeks of intoxication, although expression of CAII mRNA remained reversible. The results suggest that in the brain of the young adult, oligodendrocytes expressing message for CAII can be generated spontaneously shortly before demyelination becomes irreversible, and can survive and continue to express CAII mRNA but not CAII protein.

Subcellular distribution of carbonic anhydrase in Solanum tuberosum L. leaves: characterization of two compartment-specific isoforms

The intracellular compartmentation of carbonic anhydrase (CA; EC 4.2.1.1), an enzyme that catalyses the reversible hydration of CO2 to bicarbonate, has been investigated in potato (Solanum tuberosum L.) leaves. Although enzyme activity was mainly located in chloroplasts (87% of total cellular activity), significant activity (13%) was also found in the cytosol. The corresponding CA isoforms were purified either from chloroplasts or crude leaf extracts, respectively. The cytosolic isoenzyme has a molecular mass of 255,000 and is composed of eight identical subunits with an estimated Mr of 30,000. The chloroplastic isoenzyme (Mr 220,000) is also an octamer composed of two different subunits with Mr estimated at 27,000 and 27,500, respectively. The N-terminal amino acid sequences of both chloroplastic CA subunits demonstrated that they were identical except that the Mr-27,000 subunit was three amino acids shorter than that of the Mr-27,500 subunit. Cytosolic and chloroplastic CA isoenzymes were found to be similarly inhibited by monovalent anions (Cl-, I-, N3- and NO3-) and by sulfonamides (ethoxyzolamide and acetozolamide). Both CA isoforms were found to be dependent on a reducing agent such as cysteine or dithiothreitol in order to retain the catalytic activity, but 2-mercaptoethanol was found to be a potent inhibitor. A polyclonal antibody directed against a synthetic peptide corresponding to the N-terminal amino acid sequence of the chloroplastic CA monomers also recognized the cytosolic CA isoform. This antibody was used for immunocytolocalization experiments which confirmed the intracellular compartmentation of CA: within chloroplasts, CA is restricted to the stroma and appears randomly distributed in the cytosol.

Molecular comparison of carbonic anhydrase from Flaveria species demonstrating different photosynthetic pathways

During the evolution of C4 plants from C3 plants, both the function and intracellular location of carbonic anhydrase (CA) have changed. To determine whether these changes are due to changes at the molecular level, we have studied the cDNA sequences and the expression of CA from Flaveria species demonstrating different photosynthetic pathways. In leaf extracts from F. bidentis (C4), F. brownii (C4-like), F. linearis (C3-C4) and F. pringlei (C3), two polypeptides of M(r) 31 kDa and 35 kDa cross-reacted with anti-spinach CA antibodies. However, the relative labelling intensities of the two polypeptides differed depending on the species. Northern blot analysis indicated at least two CA transcripts are present in each Flaveria species with sizes ranging from 1.1 to 1.6 kb. Carbonic anhydrase cDNAs from all four Flaveria species studied encode an open reading frame for a polypeptide of 35-36 kDa. The amino acid sequences deduced from all four Flaveria cDNAs share at least 70% homology with the sequences of other dicot CAs. The F. bidentis (C4) CA sequence was found to be the least similar of the Flaveria proteins and, as most of the sequence dissimilarity was found in the first third of the CA molecule, these differences may be involved in the intracellular targeting of CA. A neighbour-joining tree inferred from CA amino acid sequences showed that the Flaveria CAs cluster with other dicot CAs forming a group distinct from those of monocot CAs and prokaryotic and Chlamydomonas periplasmic CAs.

Antibodies to carbonic anhydrase in patients with immune cholangiopathies

BACKGROUND/AIMS

Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have been described in autoimmune disorders. Serum from patients with immune-mediated liver diseases was studied to determine whether antibodies to carbonic anhydrase II and/or pyruvate dehydrogenase could distinguish autoimmune cholangitis as immunologically distinct from primary biliary cirrhosis.

METHODS

Antibody assays to carbonic anhydrase II (Western blot) and pyruvate dehydrogenase (flow cytometry) were performed on the sera of patients with autoimmune cholangitis (6), primary biliary cirrhosis (12), primary sclerosing cholangitis (12), autoimmune hepatitis (12), and control (Gilbert syndrome; 8).

RESULTS

Reactivity to carbonic anhydrase II was detected in 5 of 6 patients with autoimmune cholangitis, 1 of 12 patients with primary biliary cirrhosis, 1 of 12 patients with autoimmune hepatitis, and no other patients. Individuals with autoimmune cholangitis were more likely than the other patients to be reactive to carbonic anhydrase II (P < 0.001). Patients with primary biliary cirrhosis were more reactive to pyruvate dehydrogenase compared with all other groups (P < 0.001).

CONCLUSIONS

An antibody to human carbonic anhydrase II is frequently detected in the sera of patients with autoimmune cholangitis and is uncommon or not present in other cholangiopathies. These data provide evidence that autoimmune cholangitis and primary biliary cirrhosis represent distinct entities with unique patterns of immunoreactivity.

Induction of experimental autoimmune sialoadenitis by immunization of PL/J mice with carbonic anhydrase II

Experimental autoimmune sialoadenitis was induced in PL/J (H-2u) mice by intradermal immunization with human carbonic anhydrase II (CAII) and adjuvant containing monophosphoryl lipid A and trehalose diorynomycolate. Mice immunized with CAII showed a significant increase in the number and size of foci with lymphocytic infiltration in the salivary gland compared with mice immunized with adjuvant alone and untreated mice. In mice immunized with CAII, lymphocytic foci were observed around intercalated and intralobular ducts in the salivary glands, resulting in atrophy and replacement of acinar units. The epithelial cells of salivary ducts adjacent to the lymphocytic foci showed both degenerative and regenerative changes. Similar lymphocytic infiltrations were observed in the pancreas and kidney of a few mice immunized with CAII. Among several mouse strains with different H-2 haplotypes (p, q, r, s, and u), strains bearing H-2s and H-2u were susceptible to CAII-induced sialoadenitis. These results indicate that sialoadenitis induced by the immunization of CAII in mice may serve as a disease model of Sjögren's syndrome and that CAII or its derived peptides in association with the MHC may be one Ag recognized by an autoimmune response in this syndrome.

Metalloantibody design

Metal-binding sites were designed within the antigen-binding pocket of the catalytic antibody 43C9 based on a 3-dimensional antibody model and crystallographic structures of Zn-binding metalloenzymes. These tetrahedral Zn-binding sites were designed to mimic both secondary and tertiary structural characteristics of catalytic metal sites in enzymes. Each site was planned to have two His ligands across from each other on adjacent antiparallel beta-strands. Sites were selected to sequester the metal ion from bulk solvent and place an open metal coordination position next to the antigen or potential substrates. Three distinct metal-site designs, with ligands in the variable light domain, in the variable heavy domain, and in both domains, were later implemented experimentally and shown spectroscopically to bind metal ions as predicted. These results demonstrate the success of our design approach, the versatility of the antibody structure for metalloprotein design, and the validity of the 3-dimensional model. The ability to predictably design multiple metal sites in the ordered antigen-recognition region at the bottom of the pocket allows tuning of metal ion placement and enhances the likelihood of interaction with putative substrates.

Problems encountered when immunocytochemistry is used for quantitative glial cell identification in autoradiographic studies of cell proliferation in the brain of the unlesioned adult mouse

We have used sections of adult mouse brain to determine whether antibodies specific for oligodendroglia (anti-carbonic anhydrase II, CA II; anti-galactocerebroside, GC; anti-myelin basic protein, MBP) and astroglia (anti-glial fibrillary acidic protein, GFAP; anti-S 100 protein) are suitable for quantitative studies of the proliferation and subsequent differentiation of these cells. Unlesioned adult mice received a single injection of 3H-thymidine (TdR) and were killed between 1 h and 70 days later. Quantitative evaluations of autoradiographs of 2-microns-thick serial sections stained immunocytochemically with the antibodies mentioned above or with Richardson's method for histological control led to the following conclusions. Anti-GC and anti-MBP stained only the oligodendrocytic processes and, thus, cannot be used in well-myelinated brain areas. Anti-CA II stained only a portion of the differentiated oligodendrocytes, but no proliferating cells. Anti-S 100 protein recognized all the astrocytes, but also many (interfascicular) oligodendrocytes. Anti-GFAP stained only a few astrocytes in the unlesioned mouse; all astrocytes may become GFAP-immunopositive only after wounding the brain. Thus, in contrast to in vitro studies, immunocytochemical studies with these antibodies on sections of adult animals cannot be recommended for the quantitative analysis of cell proliferation. In addition, our results show that differentiated glial cells proliferate in adult mice. Astro- and oligodendrocytes divide with the same cell cycle parameters and mode of proliferation up to about 1 month after 3H-TdR injection. In contrast to oligodendrocytes, some astrocytes might re-enter the cycle after a few weeks of quiescence.

Immunohistochemical localization of carbonic anhydrase IV in capillaries of rat and human skeletal muscle

We used polyclonal antisera raised in rabbits against membrane-bound rat lung and human lung carbonic anhydrase (CA) IV in immunofluorescence studies to stain cryosections of rat soleus and extensor digitorum longus (EDL) and several human skeletal muscles. There was strong specific staining of capillaries in all muscles investigated. Several techniques were applied to verify this result. (a) Serial sections were either incubated with anti-CA IV/FITC or processed for endothelial ATPase reaction. There was precise co-localization of antibody marked structures and ATPase stained capillaries. (b) Human muscle sections were double stained with anti-CA IV/TRITC and anti-von Willebrand factor (vWF)/FITC. vWF, a capillary marker, and CA IV were localized at identical sites. (c) The CAIV was released from capillaries by treatment with phosphatidylinositol specific phospholipase C, suggesting that the enzyme is anchored to the endothelial cell membrane via a phosphatidylinositolglycan anchor. (d) A rat hindlimb was perfused with diluted antiserum. Cryosections of perfused soleus and EDL processed for anti-rabbit IgG/FITC staining showed clear fluorescence associated with capillaries, indicating that the antigen was accessible from the capillary lumen. (e) Immune complexes formed during antiserum perfusion as described in d were precipitated from muscle homogenates. SDS-PAGE followed by immunoblotting showed that the predominant portion of total muscle CA IV was bound in these complexes and therefore must be located intravascularly.

Membrane-associated carbonic anhydrase from the crab gill: purification, characterization, and comparison with mammalian CAs

Carbonic anhydrase (CA) was purified from the gills of the shore crab Carcinus maenas using affinity chromatography and HPLC. The predominantly membrane-bound CA was found to share several features with mammalian CA IV. Its apparent molecular weight of 36 kDa was reduced to 33 kDa by treatment with PNGase F, suggesting that crab CA is a glycoprotein with one N-linked oligosaccharide chain. More than half of the membrane-bound crab CA was released from membranes by treatment with a phosphatidylinositol-specific phospholipase C, indicating that the branchial CA is anchored to membrane surfaces by a phosphatidylinositol-glycan linkage. The enzyme also resembles mammalian CA IV in its relative sensitivity to inhibition by sulfonamides and the resistance to inhibition by halide ions. Amino acid composition of the HPLC-purified crab CA was examined and CNBr cleavage was carried out followed by N-terminal amino acid sequencing. Amino-terminal sequence of the native enzyme differed considerably from those of mammalian isozymes (human CA I and CA II, bovine CA III, human and rat CA IV). However, antisera raised against rat CA IV, CA II, and CA I all cross-reacted weakly with crab CA. Unlike mammalian CA IVs, crab gill CA was sensitive to 0.2% sodium dodecyl sulfate, suggesting that although crab gill CA is like mammalian CA IVs in many ways, it is less stabilized by intramolecular disulfide bonds.

Carbonic anhydrase antibody in sera from patients with endometriosis

Sera from 16 of 23 (69.6%) patients with endometriosis, a potential autoimmune disease, and 2 of 17 (11.8%) control individuals had autoantibodies against the bovine carbonic anhydrase (CA) molecular weight marker, as determined by the Western blot technique. The reactivity of these antibodies to purified human CA I, human CA II, and two preparations of bovine CA II were investigated. Of the 16 endometriosis patients who were reactive to the bovine CA molecular weight marker, 14 were reactive to at least one purified human CA isoenzyme tested, 8 were reactive to at least one purified bovine CA II, and 2 did not react with any of the CA isoenzymes tested. Variation in cross-reactivity between species and in the biochemical characteristics of various CA isoenzyme preparations may partially explain these findings. Autoantibodies to CA isoenzymes have recently been reported in other autoimmune diseases. Further investigation is required to determine the significance of CA autoantibody production in patients with endometriosis.

Immunoelectron microscopy of carbonic anhydrase isozyme VI in human submandibular gland: comparison with isozymes I and II

Carbonic anhydrase VI (CA VI) was purified from human saliva by inhibitor-affinity chromatography, and its distribution was studied in human submandibular gland by the indirect immunoperoxidase technique with a rabbit polyclonal antibody raised against the isozyme. Polyclonal antibodies to human CA I and CA II purified from erythrocytes were also raised and used for immunostaining. SDS-polyacrylamide gel electrophoresis of the purified isozymes revealed a single protein band (CA VI, 42 KD; CA I and CA II, 30 KD). Antibody raised against CA VI did not crossreact with CA I or CA II either by Western or by dot-blotting. However, antibodies against CA I and CA II showed slight crossreaction with each other's antigen by dot-blotting. In a Western blot of purified submandibular gland CA, antibody to CA VI stained the 42 and 30 KD bands, and antibodies to CA I and CA II stained the 30 KD band. The 42 KD but not the 30 KD molecule was cleaved by endo-beta-N-acetylglucosaminidase F, indicating that the former contains N-linked oligosaccharides. Immunostaining for CA VI was seen in the secretory granules and cytosol of serous acinar cells and in the duct luminal contents. Staining specific for CA II was observed in the cytosol of serous acinar and duct epithelial cells. Antibody to CA I reacted only with the walls of small blood vessels. These results suggest that (a) serous acinar cells secrete 42 KD CA VI which functions in the oral cavity and that (b) serous acinar and duct epithelial cells possess cytosolic CA (30 KD CA VI and CA II) which functions in situ.

Distribution of carbonic anhydrase isozyme III (CA-III)-positive cells in duct segments of the bovine submandibular gland

The distribution of carbonic anhydrase III isozyme (CA-III)-positive cells in bovine submandibular glands was studied by immunohistochemistry. CA-III showed strong immunoreactivity in basal cells and some lining cells of the intercalated ducts as well as in striated and interlobular ducts cells. No significant immunoreactivity could be found in other portions of the glands. Electron microscopically, the immunoreactive basal cells contained scattered tonofibrils in their cytoplasm. The distribution of CA-III suggests that the CA-III-positive basal cells may play a special physiological role, and that they do not only represent undifferentiated lining cells.

Carbonic anhydrase isoenzymes II and I are present in the zona glomerulosa cells of the human adrenal gland

Human carbonic anhydrase isoenzymes I and II (HCA I and II) were purified from human erythrocytes by inhibitor affinity chromatography and ion-exchange chromatography. These isoenzymes were then located in the human adrenal gland using specific polyclonal antisera raised in rabbits and specific detection by immunohistochemical techniques. Both HCA II and I were located in the zona glomerulosa cells, although the staining for HCA I was faint. The cells of the zona fasciculata and the zona reticularis failed to stain with either antiserum. Control stainings with preimmune or anti-HCA VI sera were negative. The presence of HCA II and I in the zona glomerulosa cells may be linked to regulation of the biosynthesis or secretion of mineralocorticoids.

Monoclonal antibodies against the C-terminal peptide of human tissue factor for studies of the cytoplasmic domain

The carboxyl-terminal cytoplasmic domain of human tissue factor (the essential cofactor for coagulation factor VII) is a prospective regulatory domain through which viable cells may control the expression of tissue factor activity. Furthermore, this domain is subject to post-translational modifications of as yet unknown functional significance. Hybridomas producing antibodies against the C-terminal domain of tissue factor were obtained using splenocytes harvested from mice immunized with a synthetic peptide corresponding to the nine terminal residues of the protein sequence. These antibodies, C28 1.1 and C28 2.1, react with purified placental tissue factor, but not with a recombinant soluble tissue factor lacking the cytoplasmic and membrane-spanning domains. This confirms that tissue factor from biological membranes contains the entire cytoplasmic domain predicted from the cDNA sequence, and provides a mechanism to determine whether tissue factor used experimentally retains this proteolytically sensitive epitope. The antibodies have been employed to demonstrate selective proteolytic removal of the carboxyl-terminal peptide from tissue factor. Limited experiments indicate that they will be useful for characterizing the distribution of vesicles with regard to the possible orientations of tissue factor on their surface.

Production of monoclonal antibodies against gastric parietal cell antigens

Two mice DBA/1 were each immunized with a single injection of one million enriched parietal cells in the hind foot pads. Monoclonal antibodies to be used as research tools in studies on regulatory mechanisms in gastric parietal cells were obtained after fusion of mouse myeloma cells (SP2) with cells from the popliteal lymph nodes of the mice. Twelve hybridomas produced antibodies reactive with structures only present in parietal cells as assessed by immunohistochemistry of oxyntic mucosa sections. Three hybridomas were subcloned and the antibodies produced by them, designated as PC4, PC8, and PC117, were characterized. In an enzyme-linked immunosorbent assay, all antibodies reacted with H,K-ATPase-containing vesicles. The antibody PC8 recognized a 94 kDa protein after immunoblotting of H,K-ATPase-containing vesicles and all antibodies precipitated a 94 kDa protein from [125I]H,K-ATPase-containing vesicles. The antibodies PC4 and PC117 recognized extracellular structures with a polarized distribution in viable, purified parietal cells. The results suggest that the structure recognized by all three antibodies is the alpha-subunit of the H,K-ATPase. The antibodies produced by another hybridoma, PC43, recognized a structure present in parietal and surface epithelial cells of the oxyntic mucosa. In an enzyme-linked immunosorbent assay, they reacted with a high-activity carbonic anhydrase which had been affinity-purified from pig oxyntic mucosa and they recognized a 30 kDa protein after immunoblotting. Thus, monoclonal antibodies against both intracellular and extracellular parietal cell structures were obtained after immunization with a small number of parietal cells.

Antibodies to carbonic anhydrase in systemic lupus erythematosus and other rheumatic diseases

OBJECTIVE

Autoantibodies to CA were demonstrated in the sera of patients with systemic lupus erythematosus (SLE) and some other rheumatic diseases. This study was undertaken to define the isoform and species specificity of these reactions, as well as to develop a method for detecting immune complexes.

METHODS

Antibodies to CA were sought by enzyme-linked immunosorbent assay (ELISA) and by Western immunoblotting.

RESULTS

An increased prevalence of CA autoantibodies was detected, by both methods, in patients with SLE, scleroderma, and polymyositis, compared with controls. In SLE patients, CA autoantibodies occurred preferentially in those with anti-U1 RNP or anti-U1 RNP and Ro/SS-A. Some sera reacted with only the CA I or CA II isoform, while approximately 50% of sera that were CA positive reacted with both isoforms. The autoantibodies reacted preferentially with the human enzymes, rather than the bovine CA, both on Western blot and by ELISA: Selected IgG F(ab')2 fragments from anti-CA-containing sera specifically inhibited the enzyme activity of CA, and the CA inhibitor acetazolamide partially inhibited the binding of anti-CA to CA. Thus, at least a part of autoanti-CA is directed toward the active site of CA. Finally, CA molecules were detected as immune complexes in sera from selected anti-CA-positive patients.

CONCLUSION

Autoantibodies to CA represent a previously unrecognized autoantibody to an abundant intracellular protein of the human erythrocyte.

Ectopic granule cell layer in mouse cerebellum after methyl-azoxy-methanol (MAM) treatment

Previous results from our laboratory (Bejar et al. 1985) indicated that a single injection in mouse pups of the antimitotic/mutagenic agent methylazoxymethanol at postnatal day 5 typically produces hypogranular cerebella with no changes in foliation, in contrast to the severe alterations observed after the more usual injection on the day of birth. Here we report that injection of a higher dose (30 mg/kg) of methylazoxymethanol, always at postnatal day 5, leads to the additional presence of a ectopic cell layer in adult cerebellum. Immunostaining with several antibodies recognizing cell specific proteins ruled out the possibility that these ectopic cells were glial and electron microscopy indicated that they were morphologically mature granule cells. In the molecular layer of other cerebellar areas and apparently unrelated with granule cell ectopia, ectopic Golgi epithelial cells were observed. The reason for the presence of these ectopic cells of different type in the molecular layer was discussed in relation with analogous ectopias obtained by other means.

A novel autoantibody reactive with carbonic anhydrase in sera from patients with systemic lupus erythematosus and Sjögren's syndrome

Carbonic anhydrase (CA) is an extremely basic zinc metalloenzyme with a wide phyletic distribution, and the enzyme is important for the regulation of acid-base status. A novel autoantibody reactive with carbonic anhydrase was demonstrated. Several different classes of CA are known in mammals. Using the immuno blotting method and and immun-dot analysis, we found this autoantibody to be reactive with CA in the sera from patients with Sjögren's syndrome (20.8%), including a patient with Sjögren's syndrome and renal tubular acidosis, and in patients with systemic lupus erythematosus (31.6%). The autoantibody varied in the extent of its cross-reactivity among human CA I (or B), human CA II (or C), bovine CA I, bovine CA II, rabbit CA, and dog CA. The titers continued to float and tended to parallel disease activity. Positive reactivity of autoantibody was observed on eccrine sweat glands and the distal tubules of the kidney by the indirect immunofluorescent method.

A high activity carbonic anhydrase isoenzyme (CA II) is present in mammalian spermatozoa

Human and rat spermatozoa were stained for different carbonic anhydrase (CA) isoenzymes using specific antisera to human CA I, II and VI in conjunction with the immunofluorescence technique. The spermatozoa of both species were found to contain only CA II, which was located principally in the postacrosomal region of the human spermatozoa and in the acrosomal cap region of the rat spermatozoa. The presence of CA II could be confirmed by immunoblotting, which revealed a 29 K polypeptide in both the human and rat spermatozoa. No CA I or VI-specific fluorescence could be detected in the spermatozoa of either species. The immunoblottings were also negative. The results show mammalian spermatozoa to contain the high activity carbonic anhydrase isoenzyme II. Its presence is probably linked to hydration of CO2 produced by active energy metabolism and thereby to the maintaining of an adequate intraspermatozoal bicarbonate concentration as required for the maintenance of sperm motility.

IgM natural autoantibodies against bromelain-treated mouse red blood cells recognise carbonic anhydrase

Carbonic anhydrase (CA) from mouse erythrocyte membranes is recognised as an autoantigen in Western blotting experiments with FUB 1, a murine IgM monoclonal antibody that binds both phosphatidylcholine and bromelain-treated mouse red blood cells (BrMRBC). Serum from mice stimulated with lipopolysaccharide (LPS-serum) also recognises CA. From SDS-PAGE, and blotting experiments with whole mouse erythrocytes, we found two closely spaced glycoprotein bands in the 30 kD region that reacted with both FUB 1 and LPS-serum. One of the molecular weight markers, bovine carbonic anhydrase which is of a molecular weight of about 30 kD, electrophoresed in the same 30 kD region also reacted with these antibodies. Carbonic anhydrases from a range of mammalian species were found to be crossreactive with FUB 1 and LPS-serum by Western blotting, whereas human glycophorin A and human asialoglycophorin were not recognised by the antibodies. FUB 1 specifically recognises both native and denatured bovine carbonic anhydrase in ELISA assays. The serological identity of the determinants of CA and BrMRBC was confirmed by specific absorption of both FUB 1 and LPS-serum with BrMRBC and normal mouse erythrocytes. We propose that a native autoantigenic epitope on erythrocytes may be revealed by the proteolytic action of bromelain and that this determinant is associated, at least in part, with carbonic anhydrase.

Metalloantibodies

A metalloantibody has been constructed with a coordination site for metals in the antigen binding pocket. The Zn(II) binding site from carbonic anhydrase B was used as a model. Three histidine residues have been placed in the light chain complementarity determining regions of a single chain antibody molecule. In contrast to the native protein, the mutant displayed metal-dependent fluorescence-quenching behavior. This response was interpreted as evidence for metal binding in the three-histidine site with relative affinities in the order Cu(II) greater than Zn(II) greater than Cd(II). The presence of metal cofactors in immunoglobulins should facilitate antibody catalysis of redox and hydrolytic reactions.

Immunohistochemical localization of carbonic anhydrase isoenzymes VI, II, and I in human parotid and submandibular glands

Human salivary carbonic anhydrase (HCA VI) was purified by inhibitor affinity chromatography and its location in the human parotid and submandibular glands identified, using a polyclonal antiserum raised against the purified enzyme in rabbits in conjunction with the peroxidase-antiperoxidase complex method. The antibodies raised against the purified enzyme in rabbits did not crossreact with the HCA II or I. However, they slightly recognized human IgA; the antiserum was therefore absorbed with human IgA before immunohistochemical use. HCA VI-specific staining was detected in the cytoplasm and particularly in the secretory granules of the serous acinar cells of both parotid and submandibular glands, the staining of the secretory granules being most distinct in paraformaldehyde-fixed tissues. Some epithelial cells and the luminal content of the striated ducts also gave a specific HCA VI staining. Staining specific for HCA II was also found in the granules of the serous acinar cells, particularly in the submandibular gland when Carnoy fluid fixation was used. Slight HCA II-specific staining was also detected in the striated ductal cells in the Carnoy fluid-fixed specimens. No staining specific for HCA I was detected. The results indicate that the serous acinar cells in human parotid and submandibular glands contain abundant HCA II and HCA VI. Interestingly, only HCA VI is secreted into the saliva, although both enzymes appear to be located in structures resembling the secretory granules in the acinar cells. The enzymes probably form a mutually complementary system regulating the salivary buffer capacity.

The 30 kDa abnormal protein in avian dystrophic muscle is indistinguishable from carbonic anhydrase III by physicochemical, immunological, and enzymological criteria

In the accompanying paper, we described the existence, molecular characterization, and ontogeny of a 30 kDa abnormal protein in chicken dystrophic muscles. In this study, we have purified chicken carbonic anhydrase III and the 30 kDa protein and directly compared them. In terms of its enzymological features, the 30 kDa protein is a typical carbonic anhydrase III. Like carbonic anhydrases, it contains one mole zinc per mole of protein. The protein selectively cross-reacted with a chicken carbonic anhydrase III antibody. Antibody to the 30 kDa protein cross-reacted with chicken skeletal muscle carbonic anhydrase III. Moreover, the distribution of the abnormal protein is exactly identical to that of carbonic anhydrase III; however, there is a possibility that the 30 kDa protein is a variant of carbonic anhydrase III. Slight differences were found in antigenicities and in the apparent molecular weights of the two proteins. We have compared the two proteins by 125I-labeled two-dimensional peptide mapping. Tryptic maps have shown that the two proteins are highly homologous. Combined, these results strongly indicate that the 30 kDa protein and carbonic anhydrase III are similar, if not identical.

A monoclonal anti-HLA-B27 antibody which is reactive with a linear sequence of the HLA-B27 protein is useful for the study of molecular mimicry

In the search for cross-reactivity between bacteria and HLA-B27, three groups of investigators have identified several bacterial envelope proteins which are reactive with the monoclonal anti-HLA-B27 antibodies B27.M1 and B27.M2. Since these two antibodies react poorly with HLA-B27-derived synthetic peptides, it is not possible to locate the reactive epitopes on the HLA-B27 using synthetic peptides. Here, we introduce Ye-2, a monoclonal anti-HLA-B27 antibody which, unlike B27.M1 and B27.M2, is reactive with a synthetic peptide derived from residues 63-84 of HLA-B27.1. Analysis with a cross-reactive peptide derived from residues 226-244 of bovine carbonic anhydrase suggests that only a few of the amino acid residues in the HLA-B27-derived peptide are responsible for the reactivity. This antibody should be a useful adjunct in a preliminary assessment of whether a bacterial protein mimics HLA-B27 in primary structure.