Monoclonal-antibodies 5g8 and 2h6 are complementary immunohistochemical markers of lung carcinomas

Two murine monoclonal antibodies (MAbs) 5G8 and 2H6 were generated by fusing spleen cells obtained from mice immunized with human fetal tissue extract (14 weeks, Nonidet P-40 membrane fraction) from the early first trimester, followed by a booster injection of a lung cancer cell line. The MAb 5G8 recognized antigens with a molecular weight of 90, 50, 20 kDa, was neuraminidase-resistant and showed cross-reactivity with both carcinoembryonic antigen and non-specific cross-reacting antigen. The MAb 2H6 reacted with a sialomucin whose molecular weight was more than 1000 kDa and was different from previously known tumor associated-marker antigens. The distribution of the MAb-recognizing antigens in various tissues was investigated immunohistochemically. In malignant epithelial tumors of the lung, acinar adenocarcinoma and bronchioloalveolar carcinoma were positive for both MAbs; papillary adenocarcinoma, squamous cell carcinoma, and adenoid cystic carcinoma were positive only for MAb 5G8; solid carcinoma with mucin formation, small cell carcinoma, and large cell carcinoma were positive only for MAb 2H6. The combination of the two MAbs covered almost all histological types of lung carcinomas (23 of 24 cases) except carcinoid tumors. MAbs 5G8 and 2H6 reacted also with a restricted number of adenocarcinomas of the other organs. MAb 5G8 did not react with normal fetal or adult tissues, except for metaplastic gastric mucosa, acinar cells of the breast and leucocytes, whereas MAb 2H6 reacted with the surface epithelium of the stomach and colon, the Brunner gland of the duodenum and uterine cervix as well as the epithelium of the fetal digestive tract. Thus, MAb 2H6 which recognized oncofetal sialomucin, played a complementary role to MAb 5G8 as a CEA-related MAb in the immunohistochemical diagnosis of lung carcinomas.     

Definition of the expression of the human carcinoembryonic antigen and non-specific cross-reacting antigen in human breast and lung carcinomas

Mouse cell lines transfected with carcinoembryonic antigen (CEA) and with 2 other members of the human CEA gene family, non-specific cross-reacting antigen (NCA) and biliary glycoprotein (BGP), were used to analyze the specificity of several monoclonal antibodies (MAbs). MAbs COL-1 and COL-6 were shown to react with the transfected CEA gene product but not with NCA, confirming previous results. Cells expressing the transfected BGP gene product also failed to react with COL-1 and COL-6. The MAb B6.2 reacted with cells expressing the NCA gene product but not with those expressing CEA or BGP. The MAb B1.1 reacted strongly with the transfected CEA and BGP gene products but only weakly with the NCA gene product. These antibodies were then utilized in the histochemical analysis of a number of primary and secondary breast and lung tumors. The results indicate that a majority of breast and lung tumors express CEA, and nearly all breast and lung tumors express NCA. Fairly homogeneous expression of CEA and NCA was seen in the majority of both breast and lung tumors. Our results indicate that CEA may be an important target for immunotherapy in a large number of patients with breast and lung tumors.     

Immunohistochemical localization and molecular characteristics of three monoclonal antibody-defined epitopes detectable on carcinoembryonic antigen (CEA)

Three murine monoclonal antibodies (MAbs) reactive to different epitopes on CEA were selected according to their ability to bind to various human tissue sections. The most selective MAb, BW 431/31, bound to the majority of colon carcinomas but only faintly to normal colon mucosa. In addition to the tissues stained by MAb BW 431/31, MAb BW 250/183 reacted with granulocytes, colon mucosa and faintly with pancreatic ducts. The third MAb, BW 374/14, reacted with granulocytes, colon mucosa, strongly with pancreatic ducts and with alveolar and bronchial epithelium. The antigenic determinants recognized by the 3 MAbs in human tissue sections were resistant to formaldehyde fixation and paraffin embedding as well as to periodic acid oxidation and neuraminidase treatment. The last two treatments suggest that the epitopes are protein in nature. Using MAb affinity chromatography, 3 antigen preparations were isolated from a human colon carcinoma xenograft with an approximate molecular weight of 180 kd. These preparations were shown to bear the epitopes from each of the MAbs and from a polyclonal antiserum specific for purified CEA. Furthermore, the ability of MAb BW 431/31 to localize its antigenic determinant in vivo on a human colon carcinoma xenograft is evaluated and its possible application in the patient is suggested.     

Cell-surface antigens of human lung tumors detected by mouse monoclonal antibodies: definition of blood-group- and non-blood-group-related antigenic systems

The pattern of antigen expression in human non-small-cell cancers of various histological subtypes has been studied. Mouse monoclonal antibodies (MAbs) were generated following immunizations with cell lines of squamous, adeno- and anaplastic large-cell carcinomas of the lung. Seven non-blood-group-related antigens were defined in addition to 5 antigens related to blood-group determinants. Detailed specificity was established with a large panel of cultured cell lines and normal and neoplastic tissues. MAb F-18 reacted in direct tests with the immunizing squamous lung carcinoma cell line, with 5 out of 5 choriocarcinoma cell lines, but with no other cell lines. No expression of F-18 antigen was observed in any normal or malignant tissue examined. The other 6 non-blood-group-reactive MAbs (F-7, F-8, F-11, F-15, F-16 and F-17) could be distinguished by their reactivity on a panel of cultured cells and tissues. One MAb in this group (F-17) reacted strongly with 19/35 lung tumor cell lines, 32/76 other tumor-derived cell lines, cultured normal kidney cells and fetal lung fibroblasts. This antibody did not react with any normal adult tissues examined, but did react with several cancer tissues including 1/17 lung tumors, 2/4 ovarian cancers and 1/5 colon tumors. Immunoprecipitation tests revealed that 5 of the antigens were glycoproteins: F-18 (Mr greater than 200,000), F-15 (Mr 44,000), F-16 (Mr 90,000), F-17 (Mr 95,000) and F-8 (Mr 95,000). Four MAbs detected Y blood-group antigen (Le(y)), only 2 of which were able to agglutinate O erythrocytes. Another antibody detected X blood-group antigen (Le(x)).     

Multidrug resistance-associated antigens on drug-sensitive and -resistant human tumour cell lines.

In this paper the biochemical properties of the antigens detected by six murine monoclonal antibodies (MAbs) are described. These MAbs react selectively with the multidrug-resistant small cell lung cancer (SCLC) cell line, H69AR, compared to its sensitive parent cell line, H69 (Mirski & Cole, 1989). Because H69AR cells do not overexpress P-glycoprotein, the antigens detected by these MAbs may be markers for non-P-glycoprotein-mediated mechanisms of resistance. We found that the 36 kDa protein precipitated by MAb 3.186 is phosphorylated and has a pI of approximately 6.7. The 55 kDa protein precipitated by MAb 3.50 is also phosphorylated and has a pI of approximately 5.7. Several observations suggest that MAbs 3.80, 3.177 and 3.187 recognise the same 47 kDa molecule and hence only MAb 3.187 was characterised further. This MAb precipitates an acidic protein which runs as a streak on isoelectric focusing gels. The 25 and 22.5 kDa cell surface proteins precipitated by MAb 2.54 both have a pI of approximately 7.6. Treatment of immunoprecipitates with glycosidase F indicated that none of the proteins detected by MAbs 2.54, 3.187, 3.50 and 3.186 have large N-linked carbohydrates. The peptide nature of the epitopes detected by MAbs 2.54 and 3.186 was unequivocally demonstrated by precipitation from in vitro translation products of H69AR RNA. The antigens detected by MAbs 3.50 and 3.187 were not detectable in immunoprecipitates of translation products but the epitopes are probably peptides because they were destroyed by boiling in sodium dodecyl sulphate. When the reaction of the MAbs with a panel of 15 paired drug-sensitive and -resistant cell lines was examined in a cell enzyme-linked immunosorbent assay, only a few resistance associated reactions were observed. Most of the reactions were either negative or not resistance-associated. When tested with three SCLC cell lines, MAb 3.187 reacted in a manner consistent with the relative resistance of the cell lines. Antigens that had similar electrophoretic mobility to those from H69AR cells were precipitated from extracts of five human cell lines of various tumour types. These data indicate that the cross-reactivities of the MAbs are due to antigens shared among the cell lines and not just the expression of common epitopes on different proteins. Resistance-associated proteins with the biochemical properties of the antigens described in this paper have not been reported previously and they remain potential markers for the as yet to be determined mechanisms of drug resistance in SCLC and other human malignancies.     

Markedly different antibody responses to immunized small cell and non-small cell lung cancer cells

Monoclonal antibodies (MoAbs) to antigens of human small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) were produced from BALB/c mice immunized with either intact cultured cells or membrane preparations from cultured tumor cells. Of 172 MoAbs produced from two NSCLC immunized mice and reactive to NSCLC cells, 137 bound staphylococcal Protein A directly, and only 11 of these 172 MoAbs were significantly reactive with cultured SCLC cells by a solid-phase radioimmunoassay. In contrast, only 16 of 99 MoAbs produced from two SCLC immunized mice and reactive to SCLC cells directly bound Protein A, and most were of an IgM isotype, but 98 of 99 of these antibodies also reacted with cultured NSCLC target plates. Twenty hybridomas producing antibodies reactive with lung cancer cells but not with a B-lymphoblastoid line were cloned. Eleven of these cloned hybridomas were from NSCLC fusions, and nine were from SCLC fusions. When representative hybridoma supernatants were tested against a broad panel of SCLC and NSCLC target plates a similar pattern was seen, with the supernatants from NSCLC-derived hybridomas only reacting strongly to the NSCLC target plates, but the supernatants from SCLC-derived hybridomas always reacting to both SCLC and NSCLC plates. We conclude that the humoral response to immunization with NSCLC cells or membrane preparations is predominantly IgG and that to SCLC is predominantly IgM. Furthermore, many IgG MoAbs reactive with NSCLC lines are poorly reactive with SCLC cells.     

Chimeric anti-N-glycolyl-ganglioside and its anti-idiotypic MAbs: immunodominance of their variable regions

P3 monoclonal antibody (MAb) is a murine IgM that specifically recognizes N-glycolyl (NeuGc)-gangliosides and sulfatides. It also reacts with antigens expressed in human breast tumors and melanoma. In syngeneic model, P3 MAb is able to elicit a strong anti-idiotypic (Ab2) antibody response, even in the absence of adjuvants or carrier proteins. 1E10 MAb is an anti-idiotypic antibody specific for P3 MAb that has demonstrated anti-tumoral effects in syngeneic and allogeneic animals. Here we report the construction of the human IgG(1) chimeric P3 and 1E10 antibodies, and the evaluation of the maintenance of the main properties of the murine MAbs. Chimeric P3 antibody specifically reacted with GM3(NeuGc) and GM2(NeuGc) gangliosides, and not with their acetylated variants. Also, it strongly recognized the anti-idiotypic 1E10 MAb. Chimeric 1E10 antibody specifically reacted with P3 MAb. Upon immunization of Balb/c mice with both chimeric antibodies, we were able to demonstrate the immunodominance of their variable regions. The anti-idiotypic response induced by both antibodies was strong and in most of the mice was even significantly higher than the anti-isotypic response, despite the fact that 70% of the chimeric molecule is xenogenic with respect to the animal model.     

Tumor markers in human renal cell carcinoma

Localization of tumor markers in human renal cell carcinomas (RCC) was studied by an immunohistochemical method using 12 different monoclonal antibodies (MAbs) recognizing carbohydrate antigens, and 2 polyclonal antibodies against S-100 protein and neuron-specific enolase (NSE), respectively. 115D8, DF3 and the MAb to epithelial membrane antigen (EMA) reacted with 9 of 13 (115D8), 6 of 13 (DF3) and 5 of 12 (MAb to EMA) cases of RCC, respectively. S-100 protein was also found in 10 of 13 cases of RCC. Further immunohistochemical studies showed that tumor cells of all 13 RCCs were strongly positive for NSE. Serum NSE levels of patients with RCC were examined by radioimmunoassay. This examination revealed that increased levels of NSE were detected in 11 of 17 sera of patients with RCC. Positive rates for patients in stages II, III and IV were 100% (10/10). On the other hand, increased levels of CA15-3 were detected in only 2 of 17 sera by enzyme immunoassay. Our results indicate that NSE may be a useful marker for human RCC, especially for those tumors that have broken through the renal capsule.     

Development of novel monoclonal antibody 4G8 against swine leukocyte antigen class I alpha chain

A mouse monoclonal antibody (MAb) was generated against swine leukocyte antigen (SLA) class I alpha chain. A newly developed series of MAb clones that react with pan leukocytes were selected and tested by immuno-histochemistry using SLA class I alpha chain expressing Cos-7 cells. Among them, MAb 4G8 was characterized by the following features: (1) 4G8 reacted with Cos-7 cells transfected with SLA class I alpha chain from the d haplotype, (2) 4G8 recognized epitopes that were different from those of commercially available anti-SLA class I MAbs 74-11-10 and PT85A, and (3) 4G8 could be used to immunostain frozen sections of thymus, spleen, lymph node, kidney, and liver tissues with good results.     

Identification of cross-reactive and restricted epitopes localized on human chorionic gonadotropin beta-subunit by monoclonal antibodies

Human chorionic gonadotropin (hCG) belongs to the family of glycoprotein hormones. All members of the family are composed of an identical alpha subunit and structurally related beta subunit which confers biological specificity. Specific quantification and functional analysis of hCG require the use of monoclonal antibodies recognizing different epitopes of hCGbeta. This study describes the production and characterization of monoclonal antibodies (MAbs) to hCGbeta with no cross-reactivity to other glycoprotein hormones. Spleen cells from Balb/c mice immunized with hCG were fused with mouse SP2/0 myeloma cells. Fused cells were grown in hypoxanthine, aminopterine, and thymidine (HAT) selective medium and cloned by limiting dilution assay. Antibody-secreting cells were screened by enzyme-linked immunosorbent assay (ELISA) and the specificity of secreted MAbs was further analyzed, using a panel of highly purified and recombinant glycoprotein hormones, their subunits and peptides representing the C-terminal end of hCGbeta (hCGbeta-CTP) by ELISA and immunoblotting. The affinity constant (K(aff)) was also determined by ELISA. Three murine hybridomas designated G5M1, B12M2 and F4M3 were obtained that secrete MAbs specific for hCGbeta. The G5M1 MAb reacts only with hCGbeta, hCGbeta-CTP and intact hCG with no detectable cross-reaction with hCGalpha or any of the other glycoprotein hormones. The specificity of B12M2 MAb is very similar to G5M1, but it does not react with hCGbeta-CTP. The F4M3 MAb also has similar specificity to G5M1 and B12M2, but it strongly cross-reacts with hLH. The affinity constant (Kaff) of G5M1, B12M2 and F4M3 was found to be 4.28 x 10(9), 5.2 x 10(8), and 1.97 x 10(9) M(-1), respectively. Our results indicate that G5M1 and B12M2 MAbs are specific for hCG and recognize epitopes restricted to hCGbeta, but F4M3 recognizes a common epitope expressed both on hCGbeta and hLHbeta.     

Active immunotherapy with 1E10 anti-idiotype vaccine in patients with small cell lung cancer: report of a phase I trial

1E10 is an anti-idiotype murine monoclonal antibody (Ab2 MAb) specific to an Ab1 MAb which reacts with NeuGc-containing gangliosides, sulfatides and with antigens expressed in some human tumors. Preparations containing this Ab2 were capable to induce a strong anti-metastatic effect in tumor-bearing mice. We conducted a Phase I clinical trial to evaluate the toxicity and humoral immune response elicited by 1E10 vaccine in patients with small cell lung cancer (SCLC). Eligible patients were those who after received chemotherapy and/or radiotherapy had partial or complete response to treatment. Patients received four biweekly injections with 2 mg of aluminum hydroxide-precipitated 1E10 MAb, then other six doses at 28-day intervals, and later the patients who maintained a good performance status were reimmunized. Six patients with limited-stage disease and three with extensive-stage disease were enrolled in the study. Most of the patients who received at least four doses of 1E10 vaccine developed strong specific antibody responses against 1E10 MAb and NeuGc-GM3 ganglioside. Antibodies able to react with lung carcinoma tissue sections were detected in sera from vaccinated patients. A prolonged survival was observed in several patients treated with the anti-idiotype vaccine. No evidence of serious adverse effects was found.     

Monoclonal antibody against human squamous-cell-carcinoma-associated antigen

Mouse monoclonal antibody (MAb) 3F8E3 (IgG3k) was developed against the head and neck cancer cell line LICR-LON-HN2. Subjected to indirect immunofluorescence, the MAb reacted exclusively with SCC cell lines and showed no reactivity with normal or transformed mouse and human non-SCC cell lines and hematopoietic cell lines. The radiolabelled MAb showed an affinity constant of 1.8 x 10(8) M-1 with HN2 cells and identified 2.07 x 10(4) sites/cell by Scatchard analysis. It identified 2 peptides from membrane extracts of HN2 cells by Western blotting. Avidin-biotin-complexed immunoperoxidase staining on cryostat sections of tumors from various tissues revealed that 3F8E3 reacted mainly with the membrane antigens of well differentiated SCC cells of oral cavity, larynx, esophagus, lung, uterine cervix, metastatic nodes of patients with oral cancer, and dysplastic cells in oral leukoplakia. The MAb did not react with poorly differentiated cells of Ca esophagus, adenocarcinoma of breast, stomach and colon, renal-cell carcinoma and soft-tissue sarcoma.     

Immunohistochemical evaluation of a panel of monoclonal antibodies for the diagnosis of small cell lung cancer

Monoclonal antibodies (mAbs) with a high sensitivity and specificity for small cell lung cancer (SCLC) may be of potential diagnostic and therapeutic use. We selected five different mAbs generated against SCLC cell lines and tested them on paraffin-embedded SCLC and non SCLC (NSCLC) clinical samples in a retrospective study using immunohistochemical techniques. The results showed that the contemporary use of mAbs that react with different antigens allowed all the examined SCLC to be detected indicating that this panel of mAbs was extremely sensitive. Analysis of the reactivity of these mAbs with NSCLC showed that 4 of the 5 antibodies reacted also with a few NSCLC. Using higher dilutions of these mAbs their specificity improved substantially. The 5 different mAbs presented marked heterogeneity of antigenic expression within and between SCLC. This panel of antibodies may be very useful in the diagnosis of SCLC whereas their application, in vivo, in therapeutic trials, is limited by the heterogeneity of antigenic expression.     

Biosynthesis and expression of the disialoganglioside GD2, a relevant target antigen on small cell lung carcinoma for monoclonal antibody-mediated cytolysis

Monoclonal antibodies (MAbs) 126 (immunoglobulin M) and 14.18 (immunoglobulin G3) react strongly with the cell surface of small cell carcinoma of the lungs (SCCL) and are unreactive with most normal tissues and other neoplasms with the notable exception of tumors derived from cells of neural crest origin. These MAbs react specifically with the oligosaccharide portion of the disialoganglioside GD2. Analysis of total gangliosides from cultured cell lines derived from SCCL indicates that GD2 is a predominant ganglioside. A comparison of the reactivities of MAbs against GD2 with those directed against gangliosides GM2 and GD3, each differing from GD2 by a single sugar residue, clearly indicates that GD2 is preferentially expressed by cultured cells derived from SCCL. Membranes isolated from these cells exhibit GD2 synthetase activity which specifically converts the precursor GD3 to GD2 in the presence of uridine diphosphate-N-acetyl galactosamine as the glycosyl donor. We present evidence that in SCCL, GD2 serves as a relevant target antigen for monoclonal antibody-mediated cytolysis. Specifically, we demonstrate that MAb 14.18 (immunoglobulin G3), can lyse small cell carcinoma of the lung targets by either complement- or antibody-dependent cellular cytotoxicity.     

Two CEA and three NCA species, although distinguishable by monoclonal antibodies, have nearly identical peptide patterns

In perchloric acid extracts of normal lung and colonic tumors, 3 NCA molecules were identified by monoclonal antibodies that cross-reacted with CEA, which itself gave 2 bands in SDS-PAGE. The proteins had molecular weights of 50, 75 and 97 kd, while the 2 CEA molecules banded at 180 and 160 kd in SDS-PAGE. No MAb recognized only one molecule, with the exception of MAb 3/13 which precipitated solely the upper CEA band. Analysis of the biochemical relationship of the cross-reactive antigens showed that none of them contained any internal methionine. Furthermore, after digestion by thermolysin, the peptide maps of the immunoprecipitated molecules showed very close similarities, if not identity. When the cross-reactive and the CEA were compared, the only differences found were in the upper CEA band, which apparently lacked one hydrophobic peptide, while the 97 kd cross-reacting protein showed one extra peptide. We conclude from our results that CEA and the cross-reacting molecules are composed of nearly identical, small (i.e. less than 50 kd) polypeptide chains.     

Generation of antibodies against prion protein by scrapie-infected cell immunization of PrP(0/0) mice

Four monoclonal antibodies (MAbs) specific for prion protein (PrP) were generated by using PrP-knockout mice immunized with a scrapie-infected mouse neuroblastoma cell line (N2a/22L). The MAbs reacted with both the cellular form (PrP(C)) and the protease K-treated form (PrP(Sc)) on Western blotting. Of the four MAbs, three recognized mouse and hamster PrP, while the remaining MAb recognized mouse, sheep, and bovine PrPs. In addition, these MAbs were shown to react only with the unglycosylated and monoglycoslated forms of PrP(Sc) in N2a/22L, but reacted with all glycosylated forms of PrP(C) and PrP(Sc) from mouse brain. This study was the first to report the development of anti-PrP MAbs using scrapie-infected cells as an immunogen and provides one approach for the generation of PrP-specific MAbs.     

Immunoreactivity of anti K562 monoclonal antibodies with leukemic cells of myeloid lineage.

Three monoclonal antibodies (MAb) raised against K562 cells (erythroleukemic cell line) reacting specifically with myeloid maturation related antigens, were characterized. MAb 4.3 (IgG2bk) reacted with promyelocytes, metamyelocytes and myelocytes, MAb 4.6 (IgG3k) also identified the myeloid blasts, while MAb 4.8 (IgG1k) reacted with metamyelocytes. The affinity constant of the MAbs ranged from 0.8 X 10(7) -3.9 X 10(8) M-1 and the binding sites on K562 cells varied from 8 X 10(4)-4 X 10(5). In competition RIA MAbs 4.6 and 4.8 competed with each other for binding sites on K562 cells. In Western blot analysis the MAbs reacted with 66,000 mol.wt and 84,000 mol.wt peptides on K562 cells and 97,000 mol.wt peptide on chronic myeloid leukemia (CML) cells. These MAbs may help in immunophenotyping of myeloid leukemias.     

Comparison of monoclonal antibodies for the detection of occult breast carcinoma metastases in bone marrow

Summary Twenty percent (n = 6) of Stage III or IV breast cancer patients (n = 30) had bone marrow metastases detected in bilateral bone marrow biopsy/aspiration preparations using standard histologic preparations. Each metastasis was also detected by four separate monoclonal antibodies (MAbs) which recognize breast carcinoma associated antigens (DF3, anti-EMA, HMFG-2, and CAM5.2). These MAbs were then utilized to stain other bone marrow preparations (n = 81) to determine their utility for the detection of micrometastatic breast carcinoma. MAbs HMFG-2, anti-EMA, and DF3 were each strongly reactive with bone marrows containing histologically-evident metastatic breast carcinoma (18/18). These anti-epithelial membrane antigen MAbs, however, were also reactive with rare plasma cells and immature cells (as well as cell clusters) in some of the control bone marrow samples tested, including those from normal patients and patients with hematologic disorders. They also reacted with some of the preparations from patients with leukemia and lymphoma, and with uninvolved marrows from patients with non-epithelial malignancies. The anti-keratin MAb CAM5.2, in contrast, reacted with 83% (15/18) breast cancer metastases and failed to stain any cells in the various categories of control marrow preparations. These data suggested that MAb CAM5.2 might be utilized to immunohistochemically differentiate micrometastatic breast carcinoma from immature myeloid or erythroid elements.Each MAb was then reacted with histologically uninvolved marrow preparations from the remaining 24 of 30 breast cancer patients in an attempt to identify occult breast carcinoma metastases. While MAbs HMFG-2, DF3, and anti-EMA demonstrated reactive cells in some of these marrows, this reactivity was similar to that seen with control preparations. MAb CAM5.2, in contrast, was negative with all specimens. These data suggest that MAb CAM5.2 may be a useful immunologic probe for the detection and confirmation of metastatic breast carcinoma in bone marrow, while more caution must be employed in the interpretation of results obtained using MAbs anti-EMA, DF3, and HMFG-2.     

Identification of a human epithelial cell surface protein sharing an epitope with the C3d/Epstein-Barr virus receptor molecule of B lymphocytes

This work examines the basis for our earlier observation that certain monoclonal antibodies (MAbs) specific for the B-cell-associated C3d/Epstein-Barr virus (EBV) receptor molecule CD21 also react with the surface of some epithelial cells. Of 9 proven anti-CD21 MAbs now examined on frozen sections of human nasopharynx, tonsil and ecto-cervix, only 3 (HB5, anti-B2, AB1) showed staining of stratified epithelium; 2 of these (HB5, anti-B2) also reacted with the surface of epithelial cells freshly dispersed from these sites. The proportion of HB5- and anti-B2-reactive cells in primary epithelial cultures fell to a low but stable level within days of explantation, while almost all permanently established epithelial cell lines, whether SV40 virus-transformed or of malignant origin, were not reactive with either MAb. This contrasts with the pattern of expression of another surface marker also found selectively on cells of the lymphoid and epithelioid lineages, the CDw40 antigen. Staining with CDw40 MAbs on epithelial sections was usually restricted to the basal (proliferating) layer, but the proportion of CDw40-positive cells increased to a relatively high level in normal epithelial cultures; furthermore, most epithelial cell lines expressed this antigen. Immunoprecipitation from the surface of metabolically labelled epithelial cells with the anti-CD21 MAb HB5 yielded a protein of approximate MW 200 kDa, clearly different in size from the 145 kDa CD21 molecule on B cells. This 200 kDa protein was identified on fresh ecto-cervical epithelium, on primary cultures of a laryngeal carcinoma and on one unusual SV40-transformed epithelial cell line. We conclude that stratified human epithelial cells express a 200 kDa surface molecule which is antigenically related to, but not identical with, the CD21 antigen on B cells. It remains to be seen whether this epithelial cell protein can function as an EBV receptor.     

Complementation of anti-CEA and anti-TAG-72 monoclonal antibodies in reactivity to human gastric adenocarcinomas

Monoclonal antibody (MAb) B72.3 and MAb COL-4 are reactive with the high-molecular-weight (Mr greater than 10(6] tumor-associated glycoprotein (TAG)-72, and the Mr 180,000 carcino-embryonic antigen (CEA), respectively. Antibody competition radioimmunoassays (RIAs) using 125I-MAb B72.3 or 125I-COL-4 have demonstrated that each MAb also recognizes a distinct antigenic determinant. Solid-phase RIAs using MAbs B72.3 and COL-4, however, demonstrated similar reactivity for each MAb with gastric carcinomas versus normal gastric mucosa. Tissue sections from all of 17 gastric adenocarcinomas also reacted with both MAb B72.3 and MAb COL-4 when immunoperoxidase techniques were used. Double-staining techniques using both MAbs on the same section were performed on formalin-fixed, paraffin-embedded gastric tissue sections using the combination of avidin-biotin peroxidase complex and avidin-biotin alkaline phosphatase complex immunohistochemical methods. The double-staining technique revealed that some carcinoma cells react with MAb B72.3, some react with MAb COL-4, and others react with both MAbs. This technique has demonstrated that more carcinoma cells can be detected by both MAbs as compared to the number of stomach carcinoma cells shown to be reactive with either one or the other MAb. These studies thus define the rationale for the use of combinations of MAbs which recognize different tumor-associated antigens as immunological adjuncts for detection and perhaps therapy of gastric carcinoma.