Characterization of a Murine Monoclonal Antibody against Human Esophageal Squamous Cell Carcinoma-Associated Antigen

A murine monoclonal antibody (MAb) 2G3 of the lgG1 type was raised using the human esophageal squamous cell carcinoma (SCC) cell line TE-2. Immunoblotting with 2G3 indicated that the antigen recognized by 2G3 has a molecular weight of 34 kD. Its activity was evaluated by immunoperoxidase and immunofluorescence on frozen and paraffin sections of various normal tissues, normal and benign tumors as well as various established cell lines. The pattern of reactivity revealed that the antigen recognized by 2G3 was expressed mainly by esophageal SCC. The only exception was represented by malignant breast tumors, where it reacted weakly. Scatchard analysis using 125I-labelled 2G3 showed that TE-2 has approximately 7.5 times more binding sites than the MCF-7 breast cancer cell line. The use of this new MAb is therefore proposed for the histopathological diagnosis of esophageal SCC.

T-Cell Chronic Lymphocytic Leukemia

A case of T-cell chronic lymphocytic leukemia (T-CLL) is reported. The surface receptor for sheep erythrocytes and acid phosphatase staining confirmed the diagnosis of T-CLL. This report provides evidence that T-CLL, a rare variant of CLL, is an aggressive disease with relative resistance to therapy and short survival.

Impaired T lymphocyte function and differential cytokine response pattern in members from cancer families

In an attempt to understand the basis of lowered natural killer (NK) and T cell functions in unaffected members from cancer families, we investigated cytotoxic T lymphocyte function (CD3-directed lysis) and the ability of the lymphocytes to respond to cytokines such as IL-2, IFN-alpha and IL-12. We observed lower CD3-mediated cytotoxic activity in these individuals supported by significantly lower numbers of circulating CD3+ lymphocytes. The cytokine treatment studies revealed impaired response to IFN-alpha and IL-12 in unaffected members and breast cancer patients. The observations presented herein not only reinforce our earlier finding that lower NK and T lymphocyte function may be a feature of cancer families, but also suggest that such impaired responses may be one of the factors contributing to lower cytotoxic potential of the circulating lymphocytes.

CD40 Ligand--an anti-apoptotic molecule in Hodgkin's disease

The expression of CD40L was investigated in HD involved lymph nodes by flow cytometry (FCM) and reverse transcriptase polymerase chain reaction (RT-PCR). Also an investigation of the role of CD40L in upregulation of the anti-apoptotic gene BclxL in a Hodgkin's disease (HD) derived cell line was undertaken. HD patients (n = 18) had significantly higher numbers of activated CD4+ and CD8+ T cells in the tumor microenvironment as compared to controls (n = 8). HD patients also demonstrated higher numbers of CD4+, CD8+ and CD19+ lymphocytes co-expressing CD40L as compared to controls. The CD40L signal was consistently and significantly upregulated in HD patients (n = 5) as compared to controls (n = 3) at the mRNA level. RT-PCR and FCM analysis revealed that soluble CD40L upregulated BclxL levels in the Fas-sensitive HD cell line HDLM2. We conclude that CD40L can act as an important anti-apoptotic molecule by upregulating BclxL expression in Reed-Sternberg cells of HD and may be partly responsible for their survival 'in-vivo'.

Circulating levels of TNF alpha and TNF receptor superfamily members in lymphoid neoplasia

We have correlated the serum levels of TNF alpha and soluble TNF receptor superfamily members with clinico-pathologic parameters in patients of Hodgkin's disease (HD, N = 26) and non-Hodgkin's lymphoma (NHLs, N = 35). HD patients had significantly higher levels of TNF alpha, sTNFRI, and sTNFRII in serum while NHL patients had significantly higher levels of sTNFRI, sTNFRII, sCD27, and sFas as compared to controls. In NHL patients the levels of sCD27 correlated directly and significantly with the high-stage disease, bone marrow involvement, lymph nodal presentation, and serum LDH levels. Similarly in NHL patients, levels of sFas also correlated directly and significantly with the presence of high stage disease. HD patients with B symptoms had significantly higher levels of sTNFRII.

IL-12 and IL-2 potentiate the in vitro tumor-specific activity of peripheral blood cells from cervical cancer patients

We have carried out a detailed analysis of the cellular immune functions of cervical cancer patients in comparison with healthy controls. It has been observed that the freshly isolated peripheral blood mononuclear cells (PBMC) exhibit natural cytotoxicity (NC) against a number of targets including tumor cells, mainly delivered by NK cells, which are non-adoptive and MHC unrestricted. Upon stimulation with cytokines like IL-2, IL-7, IL-12, IL-15 and interferons, PBMC acquire lymphokine activated killer (LAK) activity which enables them to lyse a wide range of targets including fresh tumor cells and virally infected cells. We compared the effect of IL-2 and IL-12 on enhancement of NC of PBMC from cervical cancer patients. IL-12 stimulated cultures (CD3+, CD56+) exhibited significant levels of tumoricidal activity. IL-2 stimulated lytic activity sustained even after 10 days while that of IL-12 stimulated cells declined after 6 days. Activation of PBMC was marked by increase in the expression of activation marker CD45RO and adhesion molecules LFA-1alpha, ICAM-1 and CD44. Addition of IL-12 to IL-2 stimulated cultures further enhanced the degree of lytic activity. Our data, thus, provide an evidence that PBMC from cervical cancer patients can be stimulated in response to cytokines and local or systemic treatment with low doses of cytokines may help to yield a better immune response against virus infected tumor cells in cervical cancer.

High cytosolic pool of p75 TNF receptors and delayed surface downmodulation by mononuclear cells from non-hodgkin's lymphoma patients

Analysis of the expression of TNF-Rs on fresh peripheral blood mononuclear cells (PBMNC) by Scatchard analysis showed that Gr I (stages I and II) but not Gr II (stages III and IV) NHL patients have a significantly higher expression of surface TNF-Rs than normal controls. A rapid decrease in the binding of radiolabelled anti-p75 TNF-R Mab which gradually increased after 16 h was seen in normal controls, while NHL patients showed a rapid increase in the binding of the Mab after activation of cells and a decrease in binding was observed only after 24 h. Western blot analysis for normal controls showed a weak presence of the 42 kDa fragment only, while the cytosolic extracts from fresh PBMNCs of NHL patients showed presence of both intact p75 TNF-R, as well as a 42 kDa fragment corresponding to a soluble form of p75 TNF-R. Our results suggest that increased cytosolic pools of TNF-R in NHL patients might contribute to a rapid increase in its surface expression following activation of cells.

Ceramide-induced apoptosis in fas-resistant Hodgkin's disease cell lines is caspase independent

We investigated whether cell-permeable, synthetic ceramide (C6 ceramide) could induce apoptosis in Fas-resistant Hodgkin's disease (HD)-derived cell lines. Despite strongly expressing the Fas-receptor, two of three HD-derived cell lines were resistant to Fas-mediated apoptosis. This resistance to Fas could not be attributed to differential Fas isoform generation patterns between the Fas-resistant and the Fas-sensitive cell lines. The Fas-resistant cell lines did not demonstrate the presence of Fas exon 8 deletion. Bcl-2 and BclxL levels were comparable between the Fas-resistant and the Fas-sensitive cell lines. C6 ceramide could induce apoptosis in both Fas-resistant cell lines and this was associated with a decrease in BclxL level. Caspase-1, caspase-3, or pan-caspase inhibitors could not prevent ceramide-induced apoptosis. Furthur, ceramide treatment did not lead to cleavage of caspase 3 or poly(ADP-ribose) polymerase, but caused a loss in mitochondrial transmembrane potential which could not be prevented by caspase inhibitors. Thus, we conclude that ceramide-induced apoptosis in Fas-resistant HD cell lines is caspase independent.

Immune functions, clinical parameters and hormone receptor status in breast cancer patients

We have carried out a detailed analysis of the cellular immune functions of breast cancer patients in comparison with healthy controls. A possible correlation between immune and clinical parameters was analysed in 50 breast cancer patients. Immune parameters, natural killer cell and T lymphocyte functions and the numbers of circulating T lymphocytes were analysed against the clinical parameters comprising the tumour burden, the stage of the disease and the expression of hormone receptors on the tumour. In order to analyse the immune function data effectively, low responders were identified with stringent cut-off values. Considerably higher proportions of low responders were found among the patient population. Elevated numbers of circulating T lymphocytes and CD3-directed cytolysis correlated with the expression of oestrogen receptors independently of the clinical/histological parameters.

Altered release of tumor necrosis factor and its soluble receptor in non-Hodgkin's lymphoma patients

Increased expression and elevated serum levels of tumor necrosis factor-alpha (TNF-alpha) have been shown to be associated with the presence of constitutional B symptoms and poor prognosis in non-Hodgkin's lymphoma (NHL) patients. Soluble TNF receptors (sTNF-R) are suggested to act as biological buffers in inflammatory conditions by binding and inactivating increased circulating TNF. Whereas studies have shown elevated TNF to be correlated with B symptoms, similar studies showing the status of soluble receptor release in these patients have not been conducted. Here, we show that there is increased soluble p75 TNF receptor release from peripheral blood mononuclear cells (PBMNC) in NHL patients in the early stages of the disease but it is severely depressed in patients with advanced disease. Decreased release is associated with presence of B symptoms in these patients. All NHL patients also show increased TNF secretion and a decreased rate of receptor release with time compared with healthy controls. These findings imply that decreased sTNF-R receptor release, in addition to increased TNF secretion, is also important in predisposing the patients to B symptoms. This opens up the possibility of the use of sTNF-Rs as a therapeutic tool to counter increased TNF and alleviate systemic symptoms in these patients and also as a marker for the progression of the disease.

Expression of Fas and Fas ligand in Hodgkin's disease

Fas and Fas ligand expression were investigated in twenty two cases of classical Hodgkin's disease (HD) by immunohistochemistry. While Reed-Sternberg (RS) cells in 7/22 (32%) cases expressed Fas ligand, reactive lymphoid cells expressed Fas ligand in only 2 (9%) cases. In 20/22 (91%) cases, the RS cells expressed Fas. A higher proportion of RS cells in the nodular sclerosis subtype expressed Fas as compared to the mixed cellularity subtype. In 18/22 (82%) cases, Fas expression was also noted in the reactive lymphoid cells. In eight cases, the reactive lymphoid cells were also analyzed by flow cytometry and a majority of them were CD4+CD45RO+. Most of these activated T-cells expressed Fas but were negative for Fas Ligand. To investigate the co-expression of Fas and Fas Ligand in the RS cells, six cases were subjected to Fas and Fas ligand immunostaining on consecutive sections. The co-expression was documented in the RS cells in four of six cases. These six cases with expression of both Fas and Fas ligand were investigated for the incidence of apoptosis. There was no statistically significant relationship between expression of Fas on reactive cells, expression of FasL on RS cells and the proportion of apoptotic reactive cells. In all these cases apoptosis was not observed in the RS cells. Thus Fas - FasL interactions may not lead to apoptosis of the RS cells.

CD40-ligation-mediated protection from apoptosis of a Fas-sensitive Hodgkin's-disease-derived cell line

Modulation of Fas expression and function by CD40 ligation was investigated in the Fas-sensitive human Hodgkin's disease cell line HDLM2. The recombinant human trimeric soluble CD40L (sCD40L) protected this cell line from apoptosis induced by an agonistic Fas antibody at all concentrations tested. sCD40L also protected HDLM2 when added up to 2 h after Fas ligation. Apoptosis induced by a cell-permeable synthetic ceramide could not be prevented by sCD40L. Thus, CD40 ligation is likely to intervene in the early phases of the Fas signal transduction pathway. When CD40 ligation preceded Fas ligation, it rendered the cells refractory to Fas-induced apoptosis. sCD40L-mediated protection could not be attributed to reduction in surface Fas expression, increase in Bcl-2 levels or to increase in the levels of soluble Fas isoforms.

Expression of adhesion molecules in B-cell chronic lymphocytic leukaemia: an analysis in lymphoid compartments--peripheral blood, bone marrow and lymph node

The trafficking or homing of different lymphoid subsets to particular microenvironment is mediated by specific cell adhesion molecules (CAMs) expressed on lymphocytes and endothelial cells. B-cell chronic lymphocytic leukaemia (B-CLL) or Non-Hodgkin's lymphoma of small lymphocytic, B-cell type are monoclonal expansions of mature lymphocytes. The relative distribution of the tumor lymphocytes among various lymphoid compartments vary from patient to patient. Very few studies underlying this issue are available. To this effect, we have analysed the expression of LFA-1; VLA-4, ICAM-1; CD44H and CD44v6 (haematopoietic and variant form respectively) on freshly isolated lymphocytes obtained from bone marrow (BM), peripheral blood (PB) and lymph node (LN) by flow cytometry. Overall, we find strong expression of CD44H, low to moderate expression of LFA-1, negative to low expression of VLA-4 and lack of expression of CD44v6. ICAM-1 expression was observed only in patients with prominent lymphadenopathy. Higher expression of CD44H in PB lymphoid cells relative to that of BM lymphoid cells correlated with higher PB lymphocytosis (p < 0.001). Proliferating cell nuclear antigen expression in LN sections correlated inversely with VLA-4 expression on BM and PB lymphoid cells (p < 0.05). There was no significant correlation between expression of CAMs and bcl-2 protein.

Studies on functional status of circulating lymphocytes in unaffected members from cancer families

That the inheritance of mutations in tumor susceptibility genes alone cannot determine risk for developing cancer is now well accepted. Immune functions have long been recognized as one of the important risk modifying factors in this regard. In an attempt to develop a multiparametric approach to identify high risk individuals from cancer families, we have examined NK cell function in unaffected members from familial breast cancer families. We have also carried out a parallel study of T lymphocyte functions in these individuals. Our studies demonstrate a significantly lower NK cell activity in members from cancer families. T lymphocyte activity also showed a similar trend, with the unaffected members demonstrating a notably lowered T lymphocyte function. In addition the data from patients reveals differential sensitivity of NK and T lymphocyte function to the disease phenotype. Implications of these observations are discussed.

Natural killer cell function and genetic instability in unaffected individuals from breast cancer families

Several recent reports highlight the importance of modifying factors in determining the risk for cancer of a person carrying a mutant allele of a tumour susceptibility gene. The study of two such risk modifying factors namely, natural killer (NK) cell function and constitutional cytogenetic anomalies in members of families with familial breast cancer is presented in this paper. We observed that, compared to healthy controls, a significant proportion of unaffected persons from breast cancer families not only display lower NK cell function or genetic instability alone, but also in conjunction. The significance of these observations is discussed. We propose that amongst the unaffected members, persons with lower NK cell function as well as constitutive cytogenetic anomalies may be at a higher risk for cancer. The need for a set of suitable biomarkers to identify individuals at high risk from familial breast cancer families has been recognized for many years. Constitutional cytogenetic anomalies, otherwise seen in breast tumours, have also been observed in lymphocyte cultures from unaffected persons from such families. Lowered NK cell function has previously been demonstrated in first degree relatives of cancer patients. Both these parameters have been implicated in determining the risk of developing malignancy. In the present study these aspects have been investigated simultaneously in order to assess their utility as potential biomarkers.

Augmentation of cisplatin cytotoxicity using cytokines on cervical carcinoma cell lines

We investigated whether the biological response modifiers like IFN-alpha, IFN-gamma and TNF-alpha could enhance the cytotoxic action of cisplatin on cervical carcinoma cell lines in vitro. The sensitivity of three cell lines SiHa, ME 180 and C33A to these agents was tested using colorimetric MTT assay as well as tritiated thymidine uptake. All the three cell lines demonstrated range of sensitivity to cisplatin and cytokines. Interferons and TNF when used in combination with lower dose of cisplatin showed a significant enhancement of cytotoxic action of the drug in all the cell lines. Thus these data indicate that cytokines in concert with the drug may have a potential to improve the 'in vivo' therapy in these patients.

A specific and rapid receptor assay for squamous-cell carcinoma of human esophagus

A specific radioreceptor assay, for squamous-cell carcinoma of the human esophagus, using 2G3 monoclonal antibody, has been developed for the first time. In this assay a new mathematical parameter of the Scatchard plot has been introduced for the correct measure of binding capacity (BCcm = x cos alpha). This is the perpendicular distance from the origin to the Scatchard plot line. It is always a positive quantity and is directly proportional to both the x and y intercepts for expressing the binding capacity. The assay is highly sensitive and can be used to differentiate various types of esophageal tumors such as squamous-cell carcinoma, adenocarcinoma, ulcerative growth and also a benign growth. BCcm significantly varies in the case of squamous-cell carcinoma tumors compared to adenocarcinoma and other types of tumor of the human esophagus. The assay can be completed in about 4 h and it may be used as a clinical diagnostic test.

Generation and characterization of lymphokine-activated killer cells from non-Hodgkin's lymphoma patients

Lymphokine-activated killer cells generated from peripheral blood of Non-Hodgkin's lymphoma patients showed comparable levels of cytotoxicity. The patients with advanced disseminated disease displayed better augmentation with recombinant interleukin-2 (rIL-2) than the patients with localized disease. Thus, the defective cytotoxic potential of patients could be corrected in a culture of effector cells with IL-2. The indigenous ability to produce IL-2 in response to activation of peripheral blood mononuclear cells with phytohemagglutin showed slight depression and a positive correlation with the stage of the disease. Phenotypic analysis revealed a heterogenous population of cells involved in cytotoxic activity. Thus, IL-2 merits further evaluation in malignant lymphomas, particularly in relation to other variable therapies in conjunction with chemotherapy.

In vitro modulation of natural killer cell activity in non-Hodgkin's lymphoma patients after therapy

The depressed natural killer (NK) activity, anti-body-dependent cellular cytotoxicity (ADCC) and NK cytotoxic factor cytotoxicity in untreated non-Hodgkin's lymphoma patients were found to be elevated after chemotherapy. In vitro treatment of the effector NK cells with interferon alpha could augment the NK activity in normal subjects and treated patients to a comparable degree. Chemotherapy mainly affected the post-binding events in the NK cytotoxic process by causing an increase in the active killing potential of the NK cells. This study provides a better understanding of changes in the NK cytotoxic mechanism in non-Hodgkin's lymphoma patients and the role of interferon in this process.

Unique monoclonal antibodies against soluble membrane proteins of human CML myelocytes reactive with human myeloid progenitor cells

Monoclonal antibodies of IgG1 type immunoglobulin, directed against soluble CML antigen isolated from the reactive CML peripheral myelocytes, were reported. These MAbs were further investigated for their reactivity by 125I-Protein-A binding assays, indirect immunofluorescence tests, cytotoxicity, SDS-PAGE, immunoelectrophoresis, and by immunodiffusion suggesting that they recognized antigens specific mostly to undifferentiated cells. These were tested against various leukemic peripheral blood leukocytes, bone marrow cells, established cell lines of various origin, and with many solid tumor cells and demonstrated specific reactivity with CML myelocytes alone and cell lines of myeloid origin. Indirect immunoperoxidase staining of single cell preparation revealed peroxidase localization in most promyelocytes and in few mature myelocytes from CML PBL/BM cells, thus helping in identifying the exact type (morphology) involved in reacting specifically with these MAbs.

Isolation and dissociation of immune complexes from pleural effusions of lymphoma patients

Immune complexes (IC) isolated from pleural effusions of lymphomas with favorable and unfavorable prognoses were of IgG type. These IC were further dissociated by ion exchange chromatography using 8 M urea. The antibody was found to be a high molecular weight protein (1.5 X 10(5) daltons) and reacted with antihuman IgG immunologically while a second peak obtained on ion exchange chromatography may be an antigen moiety with a molecular weight of 3.2 X 10(4) daltons as it reacted immunologically with the antibody. Strong cytoplasmic fluorescence was observed with various cell suspensions of lymphomas when reacted with the antibody preparations. The antisera raised against two different antigen fractions prepared from two lymphomas--nHL and LL showed positive fluorescence with both nHL and LL suspensions. The absorption of these rabbit antibodies with individual cell extracts or with antigen preparations also entirely blocked the cytoplasmic staining. The antigen moiety (PK-II) may have a common origin in the disease process. Pleural effusions from patients with unfavorable and favorable prognoses showed identical patterns of separation of IC components.

Natural killer and antibody-dependent cellular cytotoxicity in cervical carcinoma patients

Natural killer (NK) cell activity and antibody dependent cell-mediated cytotoxicity (ADCC) was measured in 62 untreated cervical carcinoma patients and 25 normal healthy women, using a short-term chromium release assay. A significant reduction in NK and ADCC activity was observed in disseminated disease than in localized disease, when compared with normal donors. The majority of the patients received radiotherapy and both NK and ADCC activity recovered after therapy. Furthermore, interferon-alpha was demonstrated to augment NK activity of peripheral blood mononuclear cells from healthy donors as well as patients. Also large granular lymphocytes separated on Percoll density gradient were the same in number in both the populations studied, although in cervical cancer there seemed to be a defect in killing activity.

Evaluation of circulating immune complexes in lymphomas and leukemias using two different assays

Circulating immune complexes (CICs) have been detected in the sera of patients with non-Hodgkin's lymphoma (NHL), Hodgkin's disease, chronic myeloid leukemia, and acute lymphoblastic leukemia by using C1q-binding and L1210-binding assays. Both assays gave broadly similar patterns of reactivity in terms of frequency and magnitude, though there are some differences. Significantly elevated CIC levels were observed in all pathologic groups. However, sera from NHL patients with an unfavorable prognosis consistently exhibited the highest frequency of positive values and mean CIC levels in both these assays. The two tests showed concordance in 66.6% of the NHL patients' sera and were significantly correlated. Of the sera from NHL patients 12.7% were positive in the C1q-binding assay only and 15.9% in the L1210-binding assay only. Both the assays gave positive results in some patients, and a degree of overlap indicates the presence of different types of CIC in cancer patients' sera. The combined use of two methods for detecting CICs may be useful for evaluation of the activity, the extent, and the prognosis of the malignant disease.

Pattern of subtypes of acute lymphoblastic leukemia in India

Leukemic cells from 124 acute lymphoblastic leukemia (ALL) and 31 chronic lymphatic leukemia (CLL) were examined for sheep erythrocyte receptor (E), surface immunoglobulin (SIg) and their reactivity with a panel of monoclonal antibodies recognizing specific surface antigens including pan-T, Common ALL and Ia antigens. In acute lymphatic leukemia, 33% of patients reveal T-cell receptor associated with higher age group, mediastinal mass and high WBC count. Common ALL was predominant between 2 and 9-yr age group. Among chronic lymphatic leukemia, 2 patients were found to be T-CLL while 29 revealed presence of SIg. Ia antigen was detected in 44.4% of ALL and 64% fo CLL patients. The pattern of surface marker observed in our series may be related to our life style, socio-economic and environmental factors.

A case of Sézary syndrome with non-rosetting cells and unusual cytogenetic findings

A rare case of Sézary syndrome with typical, clinical and haematological picture is described. The absence of any lymphoid surface markers on Sézary cells and the consistent presence of distinct clone 45 XY-F cytogenetic abnormality are very unusual features observed in the present case. In spite of these peculiar findings, response to chlorambucil and prednisolone was excellent.

Synthesis of immunoglobulins by biopsied tissues and cell lines from Burkitt's lymphoma

Cell suspensions of Burkitt's lymphomas and cell lines derived from the same tumours were compared for immunoglobulin synthesis by analysis of the culture fluid. Thirty-one out of fifty tumour cell suspensions (i.e. twenty-one out of thirty-five patients) synthesized IgG (γ-chains) with type κ and/or type λ light chains; IgM synthesis was found in only five cases. Of the Burkitt's lymphoma cell lines, twelve out of nineteen synthesized IgG (γ-chains); type κ light chains were produced by ten of these cell lines and type λ light chains by three. Only three cell lines synthesized μ chains. IgA synthesis was not detected in any of the biopsied tissues or cell lines.

Comparison of the immunoglobulin synthesis by the cells of the biopsied tissue and the derived cell line showed very good agreement. This leads to the conclusion that the pattern of immunoglobulins synthesized by Burkitt's lymphoma cell lines is representative of the original tumour.

Investigation of cells from repeat biopsies, and serial testing of the derived cell lines showed that the capacity to synthesize particular immunoglobulins and chains remained constant.

The fact that many of the biopsied tumour tissues and cell lines synthesized more than one immunoglobulin, or different classes of heavy chains and types of light chains, raises the question whether these immunoglobulin-producing cells originate from one or more cells.

Solubilization of IgM-kappa specific surface material from Burkitt lymphoma cell lines

Two Burkitt lymphoma (BL)-derived cell lines, characterized by the accumulation of IgM-κ reactive material in their cell membrane, and one BL-line with no such reactivity were studied. Attempts were made to isolate and further characterize the reactive membrane material. Pepain digests of crude membrane preparations from the surface reactive cell lines were capable of blocking the direct membrane fluorescence reaction while the digest obtained from the non-reactive line demonstrated no blocking activity. Gel filtered and papain digested membrane material, from all three cell lines, produced similar elution curves when rechromatographed on a calibrated Sephadex G-150 column. The membrane fluorescence blocking activity of papain digests, derived from cells with μ and κ chain reactivity, appeared to be associated with material of a molecular weight less than 50,000. When this gel filtered material, and the corresponding fraction from the non-reactive cell line, were subjected to polyacrylamide gel electrophoresis a difference in electrophoretic mobility was noted. Electron microscopy revealed small protein fragments, some of linear dimensions compatible with a molecular weight of roughly 50,000 and the majority even smaller in all three preparations. μ and κ chain reactivity was demonstrable by indirect haemagglutination only in papain digested and gel filtered fractions from the two membrane reactive cell lines. Haemagglutation inhibition with Fc μ fragments indicated that these fragments inhibited the anti-IgM reactivity of red cells coated with the proteolytic products of the two membrane reactive cell lines.

Complement-fixation test for detection of herpes-like viruses in cell cultures of Burkitt's lymphoma

Although biopsies of Burkitt's tumors contained no detectable complement-fixing (CF) antigen or antigens, tumor cell lines contained CF antigen or antigens related to the presence of a herpes-like virus particle.

Relation between Epstein-Barr viral and cell membrane immunofluorescence of Burkitt tumor cells. I. Dependence of cell membrane immunofluorescence on presence of EB virus

A comparison was made of the immunofluorescence tests for detection of cell membrane and Epstein-Barr virus antigens in cells from Burkitt tumor biopsies or continuous cultures derived therefrom. On the whole, cell membrane fluorescence in established lines appeared to depend not only upon the presence of EBV but to a considerable degree also upon the extent of the persistent viral infection. There was no constant relationship, however, between the results of the two tests and exceptions to the rule were noted. These observations indicate that different antigens are involved in the two tests. Biopsy cells in general and young cultures may reveal strong MIF activity but few, if any, EBV-positive cells. The reverse, the presence of relatively large numbers of EBV antigen-containing cells in the absence of significant MIF reactions, was also noted on occasion in a few established cultures. The possible interpretations of these findings have been discussed.