Production of functional human T-T hybridomas in selection medium lacking aminopterin and thymidine

Measurement of soluble transferrin receptor in serum of healthy adults

The concentration of soluble transferrin receptor (sTfR) in serum is reported to be useful in the diagnosis of iron deficiency, especially for patients with concurrent chronic disease, where routine tests of iron status are compromised by the inflammatory condition. A new diagnostic assay for sTfR is calibrated against natural plasma sTfR, thus minimizing calibration discrepancies that result from differences between the analyte and the cellular transferrin receptor used in other assays. Use of the new assay to measure sTfR concentrations in 225 healthy, hematologically normal adults provided a reference interval against which pathological samples could be compared. There was no difference in the reference intervals for men and women and no correlation of [sTfR] with the age of the subject. Black subjects had significantly higher concentrations than nonblacks, and people living at high altitude had higher concentrations than those living closer to sea level. These differences were additive.

A monoclonal antibody, 3/22, to rabbit CD11c which induces homotypic T cell aggregation: evidence that ICAM-1 is a ligand for CD11c/CD18

The rabbit CD11c molecule has been characterized by use of new monoclonal antibody, mAb 3/22. Expression of the p150,95 integrin (CD11c/CD18) has been shown by flow cytometry and immunohistochemistry to be restricted to monocytes, macrophages, dendritic cells and a small population of lymphocytes in peripheral blood. No expression on neutrophils could be demonstrated. Incubation of the newly derived CD8+ T cell line, BJ/873, with mAb 3/22 causes homotypic aggregation, which has been shown to be cell surface event that is not dependent on intracellular signaling or on receptor cross-linking. Inhibition studies show that the ligands responsible for this aggregation are CD11c/CD18 and ICAM-1, both of which are expressed on BJ/873. One other rabbit T cell line, K34, that also expresses p150,95 and ICAM-1, shows a similar aggregation response when stimulated with 3/22. Cell lines that express p150,95 but not ICAM-1 do not aggregate. These observations suggest that ICAM-1 is a ligand for activated p150,95.

An analysis of the expression of cyclophilin C reveals tissue restriction and an intriguing pattern in the mouse kidney

Cyclophilin C (cyp C) is a cyclosporin A (CsA) binding protein originally isolated from a mouse bone marrow stromal cell line. We have compared the expression patterns of the mammalian cyclophilins A, B, and C in mouse tissues using in situ hybridization. These studies reveal that cyp C is expressed in a restricted subset of tissues including mouse ovary, testis, bone marrow, and kidney. Within the kidney, cyp C is highly expressed in a narrow zone in the outer medulla. Using monoclonal antibodies reactive against cyp C, we find that the kidney cells expressing cyp C correspond to the S3 segment of the nephron. The S3 segment has been shown to sustain histopathological damage from high dosages of CsA, raising the possibility that cyp C may be involved in mediating this damage.

Expression of distinct desmocollin isoforms in human epidermis

Previous evidence suggested the presence of two distinct desmocollin isoforms in human epidermis. These isoforms have now been distinguished at the protein level using monoclonal and polyclonal antibodies against N-terminal fragments of desmosomal glycoprotein (DG) IV/V isolated from plantar callus and antibodies against a fusion protein containing the extracellular domain of DGII/III. Immune blotting of glycoprotein fractions from whole epidermis, plantar callus, psoriatic scales and cultured keratinocytes showed that intact DGIV/V and its proteolytic fragments consistently migrated faster than DGII/III during SDS-PAGE. The apparent Mr difference between the two isoforms was in the range 2-5 kD. DGIV/V was the predominant species in epidermal tissue but was much less prominent in cultured cells by immune-blotting and immune precipitation. This is consistent with the differentiation-related expression of desmocollins revealed by immunofluorescence. DGIV/V was strongly expressed in the upper spinous/granular layer of the epidermis whereas DGII/III was more prominent in the basal layers of the tissue. The DGIV/V monoclonal (LH50) recognized an N-terminal, Ca(++)-sensitive epitope, because its staining of unfixed epidermal tissue was markedly influenced by Ca++ levels. Ca++ inhibition was observed at concentrations as low as 50 microM, suggesting its possible physiologic significance. Ca++ inhibition of LH50 binding was also observed in an enzyme-linked immunosorbent assay system using denatured glycoproteins although higher concentrations were required. It remains to be seen whether direct effects of Ca++ on desmocollin conformation are involved in the regulation of keratinization by extracellular Ca++.

Characterization of two porcine proinsulin reactive monoclonal antibodies by immunostaining of beta-cells in pancreatic sections of different species

Murine monoclonal antibodies against porcine proinsulin were generated by somatic cell hybridization. As detected by radioimmunoassay, 2 monoclonal antibodies KSPI14D4 and KSPI13G10 showed a strong binding to 125I-labelled porcine proinsulin but not to insulin. The species specificity of these 2 monoclonals was found to be different as shown by indirect immunofluorescence using sections of Bouin-fixed pancreata of different species. The KSPI14D4 recognized the proinsulin of pig, mouse, man, cattle, rat, dog, and cat but not that of guinea pig, whereas the KSPI13G10 bound to porcine proinsulin only. From these results it is concluded that KSPI14D4 effectively recognizes a wide-spread epitope located in one of the insulin-C-peptide junctions of the proinsulin molecule, whereas KSPI13G10 is directed to a species-specific epitope of the porcine connecting peptide.

Use of monoclonal antibodies for discrimination between natural and recombinant human interferon-tau

Different monoclonal antibodies (MAbs) were raised against denaturated and native recombinant human Interferon-tau (IFN-tau). This approach gave us MAbs which recognized either N-term (prepared with SDS-denaturated IFN-tau) or C-terminal part of the antigen as well as MAbs which linked to non linear epitopes (obtained with native form of IFN-tau). Some of them inhibited or enhanced their respective binding to IFN-tau. After characterization, these antibodies were used as probes and some were selected to prepare two quantitative sensitive sandwich IRMAs able to discriminate between recombinant and natural IFN-tau.

Basal cell glycoprotein in pig epidermis closely resembles the beta 1 subunit of the integrin family of cell adhesion molecules

A 135-kD conA-binding glycoprotein isolated from pig epidermis was previously localized to the surface of basal cells in stratified epithelia using affinity-purified antibodies. Preembedding immunoperoxidase electron microscopy has now shown that this glycoprotein is concentrated on the lateral surfaces of basal cells but is not detectable on those surfaces adjacent to the basement membrane indicating a role in cell-cell rather than cell-substrate interactions. The basal cell glycoprotein was shown to resemble the beta 1 subunit of the integrin family following the generation of a specific monoclonal antibody (M5.25). The epidermal glycoprotein recognized by M5.25 and by antibodies against the beta 1 fibronectin receptor from human placenta co-migrated on SDS gels under both reducing and non-reducing conditions. Its response to disulphide reducing agents was characteristic of beta 1 integrin subunits. In addition, the basal cell glycoprotein was shown to bind to the 120-kD cell-binding fragment of fibronectin in a RGD-dependent manner. It was readily detected by immunoblotting whole cell lysates of cultured pig keratinocytes suggesting increased expression in cultured cells compared to fresh epithelial tissue. The results suggest that beta 1 integrin subunits may be involved in cell-cell interactions between basal keratinocytes in pig epidermis and that these receptors are lost from the cell surface during terminal differentiation. Thus modulation of beta 1 integrin subunit expression may play an important role in regulating differentiation in pig epidermis.

Extracellular matrix of central nervous system white matter: demonstration of an hyaluronate-protein complex

Monoclonal antibodies were raised against human glial hyaluronate-binding protein (GHAP), a major CNS-specific glycoprotein known to bind hyaluronate in vitro. Frozen sections of dog and human spinal cord were digested with Streptomyces hyaluronidase in order to ascertain whether GHAP is bound to hyaluronate in vivo. Digestion with hyaluronidase, prior to staining of the sections by conventional indirect immunofluorescence, led to a drastic reduction in the intensity of the staining reaction. Chondroitinase ABC (protease-free) was also effective in bringing about the release of GHAP from tissue sections. This enzyme also degrades hyaluronate. The effects of the chondroitinase were completely reversed by the addition of 1 mM Zn2+, a known inhibitor of this enzyme. The intact protein was released into the soluble fraction of human brain homogenates by testicular hyaluronidase. An immunoreactive species of 70 kD was released into the soluble fraction of dog spinal cord homogenates by Streptomyces hyaluronidase. Dog GHAP was isolated from spinal cord by means of ion exchange and affinity chromatography. This protein bound efficiently to hyaluronate in vitro. Dog and human GHAP had identical isoelectric points and similar peptide maps but different molecular weights. Dog GHAP (70 kD) was larger than its human counterpart (60 kD). These findings imply that GHAP exists in association with hyaluronate in CNS white matter. Immunoelectron microscopy revealed that GHAP fills the space between myelin sheaths in dog spinal cord white matter. One is led to conclude therefore that an hyaluronate based extracellular matrix exists in CNS white matter.

Isolation of subpopulations of murine epidermal cells using monoclonal antibodies against differentiation-related cell surface molecules

Monoclonal antibodies (mAbs) against epithelial cells were prepared by immunization of rats with lyophilized murine epithelia. Screening against tissue sections and epithelial cell suspensions permitted identification of mAbs against surface molecules that are expressed early in cell differentiation. Staining with these mAbs followed by fluorescence-activated cell sorting enabled isolation of subpopulations of basal epithelial cells. Staining these subpopulations with antibodies against known differentiation markers (cytokeratins and bullous pemphigoid antigen) and measurements of cell size indicated that they represented fractions of the basal cell population in sequential stages of early differentiation. Labeling mice with bromodeoxyuridine at various times prior to cell isolation showed that the least-differentiated basal cells cycle more slowly than those at later stages, data which support the concept of a differentiation-related, hierarchical pattern of organization of the proliferative compartment.

p185HER2 monoclonal antibody has antiproliferative effects in vitro and sensitizes human breast tumor cells to tumor necrosis factor

The HER2/c-erbB-2 gene encodes the epidermal growth factor receptorlike human homolog of the rat neu oncogene. Amplification of this gene in primary breast carcinomas has been show to correlate with poor clinical prognosis for certain cancer patients. We show here that a monoclonal antibody directed against the extracellular domain of p185HER2 specifically inhibits the growth of breast tumor-derived cell lines overexpressing the HER2/c-erbB-2 gene product and prevents HER2/c-erbB-2-transformed NIH 3T3 cells from forming colonies in soft agar. Furthermore, resistance to the cytotoxic effect of tumor necrosis factor alpha, which has been shown to be a consequence of HER2/c-erbB-2 overexpression, is significantly reduced in the presence of this antibody.

Heterogeneity of the L-rhamnose residue in the outer core of Pseudomonas aeruginosa lipopolysaccharide, characterized by using human monoclonal antibodies

Hybridoma cell lines producing human monoclonal antibodies (MAbs) MH-4H7 and KN-2B11 [immunoglobulin M (lambda)] which bound to the outer core region of Pseudomonas aeruginosa lipopolysaccharide (LPS) were established by cell fusion of human peripheral lymphocytes with human-mouse heteromyeloma SHM D-33. Both binding specificity experiments with a series of LPS-defective mutants derived from P. aeruginosa PAC1R (P. S. N. Rowe and P. M. Meadow, Eur. J. Biochem.132:329-337, 1983) and competitive enzyme immunoassay experiments with monosaccharides demonstrated that alpha-L-rhamnose residues in the outer core of LPS might be in part an epitope. The MAbs specifically bound to clinical isolates belonging to Homma serotypes A, F, G, and K at a frequency of 70 to 86% and to serotypes H and M isolates at about 50%. They did not bind to any isolates of serotype B, E, and I tested. This evidence indicates that L-rhamnose and probably its neighboring residues in the other core of P. aeruginosa are heterogeneous in some association with the O serotype.

An alternative method for the isolation of NS-1 hybridomas using cholesterol auxotrophy of NS-1 mouse myeloma cells

We have used the cholesterol auxotrophy of NS-1 mouse myeloma cells as the basis for selecting NS-1 hybridomas. The outgrowth of nascent NS-1 hybridomas in cholesterol-free serum-free medium was 3- to 9-fold more efficient than that in HAT medium and resulted in 3- to 13-times as many antigen-reactive hybridoma wells. This method of hybridoma selection can be applied with any sterol-dependent parent cell line. Hybridomas established under serum-free culture conditions were growth inhibited by fetal calf serum.

p185HER2 monoclonal antibody has antiproliferative effects in vitro and sensitizes human breast tumor cells to tumor necrosis factor

The HER2/c-erbB-2 gene encodes the epidermal growth factor receptorlike human homolog of the rat neu oncogene. Amplification of this gene in primary breast carcinomas has been show to correlate with poor clinical prognosis for certain cancer patients. We show here that a monoclonal antibody directed against the extracellular domain of p185HER2 specifically inhibits the growth of breast tumor-derived cell lines overexpressing the HER2/c-erbB-2 gene product and prevents HER2/c-erbB-2-transformed NIH 3T3 cells from forming colonies in soft agar. Furthermore, resistance to the cytotoxic effect of tumor necrosis factor alpha, which has been shown to be a consequence of HER2/c-erbB-2 overexpression, is significantly reduced in the presence of this antibody.

Hybridoma-derived human suppressor factors: differential effects on mouse lymphocytes

We have recently identified a family of suppressor factors produced by certain human T-T cell hybridomas that we developed (references 1 and 2) and by the Jurkat T cell line. These suppressor factors significantly inhibited proliferative responses to mitogens and allogeneic cells in mixed lymphocyte culture and antibody production by human peripheral blood mononuclear cells. We investigated and report here the effect of these suppressor factors on certain in vitro murine immune responses. Suppressor factors produced by certain of these hybrids, such as 153, 160, 170 and by the Jurkat T-cell line were able to inhibit: (1) proliferative responses to mitogens of mouse thymocytes and splenocytes; (2) proliferative responses of mouse splenocytes to allogeneic cells in mixed lymphocyte cultures; (3) primary in vitro antibody responses of mouse spleen lymphocytes to sheep erythrocytes; (4) primary in vitro antibody responses of mouse spleen lymphocytes to a T-cell independent antigen (TNP-Ficoll). Inhibition of murine immune responses in vitro by these suppressor factors was regular and reproducible and it was observed in a large number of experiments. In contrast, suppressor factors produced by the 169 and by the 77(38F3) hybrids did not suppress the murine immune responses. The basis for these differences are not known at the present. The ability of human suppressor factors to inhibit effectively mouse immune responses provides an additional opportunity for the characterization of the properties of these factors in vivo using mouse models of human disease.

Preparation and characterisation of monoclonal and polyclonal antibodies to maize membrane auxin-binding protein

Binding proteins, thought to be auxin receptors, can be solubilised from maize (Zea mays L.) membranes after acetone treatment. From these crude extracts, receptor preparations of over 50% purity can be obtained by a reliable, straight-forward procedure involving three chromatographic steps - anion exchange, gel filtration and high-resolution anion exchange. Such preparations have been used to immunise rats for subsequent production of monoclonal antibodies. By the further step of native polyacrylamide gel electrophoresis the semi-purified preparations yield homogeneous, dimeric (22-kilodalton, kDa) auxin-binding protein, which has been used to produce a polyclonal rabbit antiserum. The preliminary characterisation of this antiserum and of the five monoclonal antibodies is presented. Two of the monoclonal antibodies specifically recognise the major 22-kDa-binding protein polypeptide whilst the other three recognise, in addition, a minor 21-kDa species. All the monoclonal antibodies recognise the polypeptide rather than the glycan side chain and the polyclonal antiserum also recognises deglycosylated binding protein. The antibodies have been used to quantify the abundance of auxinbinding protein in a number of tissues of etiolated maize seedlings. Root membranes contain 20-fold less binding protein than coleoptile membranes.

Interleukin 2 activation of natural killer cells rapidly induces the expression and phosphorylation of the Leu-23 activation antigen

IL-2 potentiates both growth and cytotoxic function of T lymphocytes and NK cells. Resting peripheral blood NK cells can respond directly to rIL-2, without requirement for accessory cells or cofactors, and enhanced cytotoxicity can be measured within a few hours after exposure to this lymphokine. In this study, we describe an activation antigen, Leu-23, that is rapidly induced and phosphorylated after IL-2 stimulation of NK cells and a subset of low buoyant density T lymphocytes. Previously, it has been uncertain whether all NK cells or only a subset are responsive to IL-2. Since within 18 h after exposure to IL-2, essentially all NK cells express Leu-23, these findings indicate that all peripheral blood NK cells are responsive to stimulation by IL-2. The Leu-23 antigen is a disulfide-bonded homodimer, composed of 24-kD protein subunits with two N-linked oligosaccharides. Appearance of this glycoprotein on NK cells is IL-2 dependent and closely parallels IL-2-induced cytotoxicity against NK-resistant solid tumor cell targets.

A new method for the development of human T-T cell hybrids without the use of HAT medium

We report here a new method for the development of human T-T cell hybrids by fusing mitogen- or alloantigen-stimulated T cells with non-mutagenized cells from human lymphoblastoid T cell lines. This method is based on a new selection procedure where the hybrids are separated from the parent T cell line on the basis of their ability to form colonies in soft agar. In contrast, cells from lymphoblastoid T cell lines Molt-4 and Jurkat do not form colonies in agar. Hybridoma colonies are retrieved from the agar plates, expanded in culture, screened by HLA-typing and appropriate functional tests and recloned several times by limiting dilution. HAT medium, which contains thymidine that appears to be toxic to the hybrids, is not used in our selection procedure. Using this method, we developed human T-T cell hybridomas (as determined by HLA-typing) producing B-cell growth factor (BCGF) either constitutively or after induction with Concanavalin A (Con A). Certain other T-T cell hybrids produced suppressor factor, significantly inhibiting proliferative responses of human peripheral blood mononuclear leukocytes to PHA, Con A and allogeneic cells in mixed lymphocyte culture.

Immunological analysis of mucin molecules expressed by normal and malignant mammary epithelial cells

Many existing MAbs raised against the human milk fat globule or against carcinoma cells recognise epitopes on high-molecular-weight glycoproteins. In a comparative ELISA assay a number of these antibodies have been shown to react with an extract of the human milk fat globule. In comparative immunoblots of cultured normal milk cells and breast cell lines, all were found to bind to large molecules which show some variation in molecular weight depending on the cell source. The HMFG-2 antibody, which is widely used in cancer diagnosis, also recognises epitopes on lower-molecular-weight components. In T47D cells these may be as small as 80,000 Mr, and with electron microscopy this cell line can be shown to accumulate HMFG-2-reactive components in the Golgi apparatus. Using an HMFG-2 affinity column we have immunopurified HMFG-2-reactive material from the 2 breast cancer cell lines MCF-7 and T47D and shown that all of the above antibodies react in a solid-phase ELISA with the purified material. In addition to high-molecular-weight components, the immunopurified material was found to contain lower-molecular-weight components including a glycoprotein of 68,000 Mr that was not, however, recognised by the HMFG-2 antibody on a Western blot. We have used this immunopurified material to generate new MAbs. All of these recognise the high-molecular-weight bands seen with the other antibodies, but 2 of them also recognise a band at 68,000 Mr in blots of MCF-7 and T47D. The second-generation antibodies show a spectrum of reactivity on tissues similar to HMFG-2 and one reacts at least as strongly as HMFG-2 with methanol-acetone-fixed sections of breast cancers.

Murine monoclonal antibodies defining neutralizing epitopes on tumor necrosis factor

A panel of four monoclonal antibodies (MAbs) was generated against recombinant human tumor necrosis factor-alpha (rTNF). These MAbs immunoprecipitate 125I-labeled rTNF, block binding of 125I-labeled rTNF to L929 mouse fibroblasts, and neutralize in vitro cytotoxicity of rTNF and native TNF (nTNF) in the L929 cytotoxicity assay. They define distinct epitopes closely associated with the receptor binding site of rTNF. In Western analysis they bind to both monomeric and dimeric rTNF. Two MAbs recognizing distinct epitopes were used to develop a 'sandwich' enzyme immunometric assay (EIMA) to measure rTNF levels in human serum and other fluids.

Characterization of murine monoclonal antibodies that recognize neutralizing epitopes on human C5a

We generated a panel of 10 murine monoclonal antibodies (MAbs) that recognize human complement fragment C5a. These MAbs were characterized for their ability to immunoprecipitate 125I-labeled C5a, bind C5a in solid-phase enzyme immunoassay, and block 125I-labeled C5a binding to polymorphonuclear leukocytes. Four of these MAbs had affinity constants for C5a in the 1 X 10(9) to 3 X 10(9) M-1 range. These MAbs blocked C5a-induced neutrophil polarization and chemiluminescence. They blocked the ability of passively administered C5a to cause neutropenia in rabbits. These anti-C5a neutralizing MAbs may have potential therapeutic use in states of complement activation.

HTLV-I--associated B-cell CLL: indirect role for retrovirus in leukemogenesis

Serum containing antibodies to the human T-lymphotropic virus type I (HTLV-I) has been observed at a higher than expected frequency in patients with B-cell chronic lymphocytic leukemia (CLL) in an area endemic for HTLV-I. An attempt was made to determine whether the cells from patients with this leukemia were HTLV-I antigen-committed B cells that had undergone malignant transformation. Cells from two HTLV-I seropositive Jamaican patients with CLL were fused with a human B-lymphoblastoid cell line. The hybridoma cells that resulted from the fusion of CLL cells from patient I.C. produced an immunoglobulin (IgM) that reacted with the p24 gag protein from HTLV-I, HTLV-II, and HTLV-III (now referred to as HIV), but showed preferential reactivity with HTLV-I. The specific immunoglobulin gene rearrangement (IgM, kappa) in the CLL cell was demonstrated in the hybridoma cell line, indicating that the captured immunoglobulin was from the CLL cells. The IgM secreted by the fusion of CLL cells from patient L.L. reacted only with HTLV-I-infected cells and with the HTLV-I large envelope protein (gp61) on Western blots. The CLL cells from these patients appear to be a malignant transformation of an antigen-committed B cell responding to HTLV-I infection, suggesting an indirect role for this retrovirus in leukemogenesis.

Polyomavirus small t antigen: overproduction in bacteria, purification, and utilization for monoclonal and polyclonal antibody production

Polyomavirus small t antigen was purified from genetically engineered Escherichia coli and used as the immunogen for the production of polyclonal and monoclonal antibodies. A new series of plasmids for increased expression of polyomavirus T antigens or a T antigen-beta-galactosidase fusion protein was constructed by replacing sequences coding for the ribosome-binding site of previously published plasmids with a chemically synthesized sequence that has a higher degree of complementarity to the 3' end of the 16S rRNA. Cells expressing the fusion protein from the plasmid with the synthetic sequence contained 5- to 10-fold more fusion protein after a 3-h induction than did control cells. Pulse-labeling of cells bearing the new plasmids revealed that the T antigens were synthesized at high levels after induction: 10% of total synthesis for small t; 15% for Py-1387T middle T, a truncated mutant of middle T; and probably 1 to 5% for middle T. Small t and Py-1387T middle T, but not wild-type middle T, were seen as minor bands in total cell protein analyzed on sodium dodecyl sulfate-polyacrylamide gels stained with Coomassie blue. A simple, rapid procedure for purification of bacterial small t from the pellet of sonicated bacteria yielded 1 to 2 mg of small t per liter of bacterial culture at 80 to 90% homogeneity. High-titer polyclonal rabbit antisera raised against purified small t recognized all three T antigens and were suitable for immunoaffinity purification of middle T. Mouse monoclonal antibodies raised against bacterial small t were of four classes, immunoprecipitating either all three polyomavirus T antigens, small t and middle T only, primarily small t, or middle T and large T in preference to small t. One of the latter monoclonal antibodies also immunoprecipitated large T but not small t of simian virus 40, suggesting that the site recognized by this antibody may be functionally important. None of the monoclonal antibodies yielded an immunoprecipitate active in phosphorylating middle T in vitro.

Monoclonal antibodies to transthyretin

Monoclonal antibodies (mabs) have been raised against human transthyretin (hTTR). The protein was isolated by an affinity chromatography procedure using Sepharose-hRBP and BALB/c mice were immunized. Following fusion with SP 2/0 myeloma cells, 26 single cell clones producing antibodies against hTTR were isolated. These mabs have been characterized and efforts have been made to establish the epitopes that they recognize. So far at least two different epitopes have been identified both residing in a mid-region fragment corresponding to the amino acid sequence 35-103 of the hTTR subunit. All mabs have been found suitable for immunohistochemical localization of hTTR even in formaldehyde fixed and paraffin embedded tissues.

Species-specific monoclonal antibody to a 43,000-molecular-weight membrane protein of Mycoplasma pneumoniae

A murine immunoglobulin G1 monoclonal antibody was produced that binds to a protease-sensitive, periodate-insensitive epitope on a 43,000-molecular-weight Mycoplasma pneumoniae membrane polypeptide. The 43,000-molecular-weight polypeptide appeared to be a major antigenic component of M. pneumoniae, as determined by immunoblot analysis. This monoclonal antibody reacted with 33 different clinical isolates of M. pneumoniae, but not with normal-flora Mycoplasma species or 18 other microorganisms potentially inhabiting the normal or diseased human respiratory tract. This apparent species-specific monoclonal antibody may have application for the detection of M. pneumoniae antigen in clinical specimens.

Enhanced formation of mouse hybridomas without hat treatment in a serum-free medium

A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without the need for hypoxanthine-aminopterin-thymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in serum- and HAT-containing medium or are masked by serum.

Monoclonal antibodies specific for adenovirus early region 1A proteins: extensive heterogeneity in early region 1A products

Hybridomas secreting monoclonal antibodies specific for the adenovirus early region 1A (E1A) proteins were prepared from BALB/c mice immunized with a bacterial trpE-E1A fusion protein. This protein is encoded by a hybrid gene that joins a portion of the Escherichia coli trpE gene and a cDNA copy of the E1A 13S mRNA (Spindler et al., J. Virol. 49:132-141, 1984). Eighty-three hybridomas that secrete antibodies which recognize the immunogen were isolated and single cell cloned. Twenty-nine of these antibodies are specific for the E1A portion of the fusion protein. Only 12 of the monoclonal antibodies can efficiently immunoprecipitate E1A polypeptides from detergent lysates of infected cells. E1A polypeptides were analyzed on one-dimensional, sodium dodecyl sulfate-polyacrylamide gels and two-dimensional, isoelectric focusing polyacrylamide gels. The E1A proteins that are specifically immunoprecipitated by the monoclonal antibodies are heterogeneous in size and charge and can be resolved into approximately 60 polypeptide species. This heterogeneity is due not only to synthesis from multiple E1A mRNAs, but also at least in part to post-translational modification. Several of the monoclonal antibodies divide the E1A polypeptides into immunological subclasses based on the ability of the antibodies to bind to the antigen. In particular, two of the monoclonal antibodies bind to the polypeptides synthesized from the 13S E1A mRNA, but not to other E1A proteins.

Epstein-Barr virus-encoded protein found in plasma membranes of transformed cells

We have developed monoclonal antibodies to a 63,000-molecular-weight protein (p63) which is the product of the most abundant messenger RNA in Epstein-Barr virus-transformed cells and shown that the protein is associated specifically with plasma membranes. It was also found to be associated with the other membrane fractions and was found in all Epstein-Barr virus-transformed cells tested. In addition, p63 was present in virions, resulting in transient, early appearance in newly infected cells. Newly synthesized p63 was detected at the time cells underwent blast transformation (48 to 72 h postinfection). The possible role of this protein in transformation and as a target for cell-mediated cytotoxicity is discussed.

Discordance between surface and cytoplasmic expression of the Leu-4 (T3) antigen in thymocytes and in blast cells from childhood T lymphoblastic malignancies

We have examined the expression of the Leu-4 (T3) antigen on the cell surface and in the cytoplasm of blast cells from 23 patients with T cell acute lymphoblastic leukemia and T cell lymphoblastic lymphoma. In the majority of cases (17), the Leu-4 antigen was absent from the cell surface; however, in 16 of these 17 cases, blast cells demonstrated cytoplasmic expression of Leu-4. This discordance between surface and cytoplasmic expression of Leu-4 was also found in thymocytes and appeared to be restricted to Leu-4, in that tests of other T cell antigens rarely revealed discordance between surface and cytoplasmic expression. To study further the cytoplasmic determinant identified by anti-Leu-4 in malignant T lymphoblasts, immunoprecipitation studies were performed that utilized biosynthetic labeling of established T cell lines derived from T lymphoblastic malignancies. By one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, identical Leu-4 polypeptide families were immunoprecipitated from surface Leu-4+ and surface Leu-4-/cytoplasmic Leu-4+ cell lines. Because T lymphoblastic malignancies represent proliferations of immature T cells, and because the cases studied demonstrated surface phenotypes corresponding to all of the proposed stages of T cell ontogeny, it appears that cytoplasmic expression of Leu-4 occurs early in T cell development. The reason for the failure of these immature T cells to transport the Leu-4 molecule to their surface remains to be elucidated.

A novel human lymphokine that inhibits haematopoietic progenitor cell proliferation

T lymphocytes in culture synthesize and secrete a variety of factors that activate and guide the differentiation, replication and maturation of haematopoietic cells in vitro. Malignant T-cell lines as well as T-cell hybridomas producing several of these factors have been established. We report here a factor produced by a human cell line that exerts a potent inhibitory effect on the growth of bone marrow progenitor cells. The properties of this factor, which we have termed colony-inhibiting lymphokine ( CIL ), differ from other inhibitors of haematopoietic progenitor cell proliferation, but resemble those of a T-cell-derived factor causally linked with some cases of severe aplastic anaemia in humans. Sensitivity of cells to this factor appears to correlate positively with expression of HLA-DR surface antigens.

Isolation of hybridomas expressing a specific heavy chain variable region gene segment by using a screening technique that detects mRNA sequences in whole cell lysates

A technique is described that allows single hybridoma cell colonies to be assayed for the productive rearrangement of a single immunoglobulin variable region (V) gene segment by utilizing expression of V mRNA for analysis. Hybridomas growing in microwell tissue culture plates are lysed in situ, cellular RNA is directly transferred to nitrocellulose by filtration, and specific immunoglobulin mRNA is detected by hybridization of the filter with a DNA probe. The method is simple and sensitive. A single species of mRNA can be detected in a lysate of 1000 cells; 5000 hybridoma colonies can be easily screened per day. The technique has been successfully used to isolate cell lines from nonimmune mice expressing a particular heavy chain variable region (VH) gene segment.

Spontaneous release of the Leu-2 (T8) molecule from human T cells

Sensitive enzyme-linked immunosorbent assays (ELISA) for the detection of human T cell antigens in soluble form have been developed. The assays use mouse monoclonal antibodies and specific anti-Leu sera prepared in rabbits by immunizing with Leu antigens absorbed to monoclonal antibody affinity columns. With these assays, Leu-1, -2, and -3 antigen signals from extracts of as few as 5 X 10(3) cells could be detected. When culture supernatants from various cell lines were tested, Leu-2 antigen, but not Leu-1 or Leu-3, was found to be present. Leu-2 antigen was present only in supernatants from T cell lines that expressed Leu-2 on their cell surface. Leu-2 antigen accumulated progressively in the supernatant of low density culture and its presence did not depend on cell proliferation or on fetal calf serum in the culture medium. The Leu-2 antigen in the supernatant was found to have only one Leu-2a determinant, whereas Leu-2 antigen from cell extracts had at least two determinants. The Leu-2 molecule was effectively purified from supernatant with an anti-Leu-2a affinity column. The purified Leu-2 antigen from supernatant of HPB-ALL cells was a single polypeptide chain of 27,000 mol wt, whereas Leu-2 antigen present on HPB-ALL cell surface was composed of two or more identical polypeptide chains of 33,000 mol wt linked by disulfide bonds. Normal human sera and sera from leukemia patients were also examined for the presence of the Leu-2 antigen. Normal human sera contained low levels of Leu-2 antigen but sera from Leu-2-positive leukemia patients had high levels. These results indicate that Leu-2 antigen is released from human T cells under physiological conditions.