Immune and non-immune control of neoplastic development: contrasting effects of host and tumor evolution

Polycyclic Aromatic Hydrocarbon Levels in Wistar Rats Exposed to Ambient Air of Port Harcourt, Nigeria: An Indicator for Tissue Toxicity

This study investigated the PAH levels in Wistar rats exposed to ambient air of the Port Harcourt metropolis. Twenty Wistar rats imported from a nonpolluted city (Enugu) were exposed to both indoor and outdoor air. Following the IACUC regulation, baseline data were obtained from 4 randomly selected rats, while the remaining 16 rats (8 each for indoor and outdoor) were left till day 90. Blood samples were obtained by cardiac puncture, and the PAH levels were determined using Gas Chromatography Flame-Ionization Detector (GC-FID). GraphPad Prism (version 8.0.2) Sidak's (for multiple data set) and unpaired t-tests (for two data sets) were used to evaluate the differences in group means. Seven of the PAHs found in indoor and outdoor rats were absent in baseline rats. The mean concentrations of PAH in indoor and outdoor animals were higher than those of baseline animals, except for Benzo(a)pyrene, which was found in baseline animals but absent in other animal groups. Additionally, Dibenz(a,h)anthracene, Indeno(1,2,3-c,d)pyrene, Pyrene, 2-methyl, and other carcinogenic PAHs were all significantly higher (p < 0.05) in outdoor groups. The vulnerable groups in Port Harcourt are at the greatest risk of such pollution. Therefore, urgent environmental and public health measures are necessary to mitigate the looming danger.

cDNA cloning, genomic structure and expression analysis of the goose (Anser cygnoides) MHC class I gene

To provide data for studies on avian disease resistance, goose MHC class I cDNA (Ancy-MHC I) was cloned from a goose cDNA library, it's genomic structure and expression analysis were investigated. The mature peptides of Ancy-MHC I cDNA encoded 333 amino acids. The genomic organization is composed of eight exons and seven introns. Based on the genetic distance, six Ancy-MHC I genes from six individuals can be classified into four lineages. A total of nineteen amino acid positions in peptide-binding domain showed high scores by Wu-kabat index analysis. The Ancy-MHC I amino acid sequence displayed seven critical HLA-A2 amino acids that bind with antigen polypeptides, and have an 85.4-98.9% amino acid homology with each genes, and a 59.8-66.0% amino acid homology with chicken MHC class I. Expression analyses using Q-RT-PCR to detect the tissue-specific expression of Ancy-MHC I mRNA in an adult goose. The result appeared that Ancy-MHC I cDNA was expressed in the liver, spleen, intestine, kidney, lung, pancreas, heart, brain, and skin. The phylogenetic tree appears to branch in an order consistent with accepted evolutionary pathways.

cDNA cloning and genomic structure of the duck (Anas platyrhynchos) MHC class I gene

In order to provide data for studies on disease resistance, duck MHC class I cDNA (Anpl-MHC I) was cloned from a duck cDNA library and the genome structure was investigated. Anpl-MHC I genes encoded 344-355 amino acids. The genomic organization is composed of eight exons and seven introns. Based on the genetic distance, Anpl-MHC I cDNA from six individuals can be classified into four lineages (from Anpl-UAA to Anpl-UDA). A total of 28 amino acid positions in the peptide-binding domain (PBD) showed high scores by Wu-kabat index analysis. The Anpl-MHC amino acid sequence displayed seven critical HLA-A2amino acids that bind with antigen polypeptides, and have an 83.6-88.5% amino acid homology with each lineage, a 55.2-64.6% amino-acid homology with chicken MHC class I (B-FIV21, B-FIV2, Rfp-Y), and a 40.3-42.8% homology with mammalian MHC class I. Nested PCR detected that Anpl-MHC I can be expressed in the brain, heart, kidney, intestines and bursa. Compared with the human HLA-A2 tertiary structure of the PBD, Anpl-MHC I had an insertion or deletion variation in four domains (A-D). The phlyogenetic tree appears to branch in an order consistent with accepted evolutionary pathways.

Immunopathology of in situ seminoma

In this study of the seminomatous human testis the composition, activity and apoptosis of lymphocytes infiltrating the immune-privileged seminiferous tubules with in situ seminoma were studied by immunohistochemistry and DNA fragmentation detection. Likewise the lymphocytes infiltrating the invasive seminomas were studied. The study showed equal numbers of CD4+ and CD8+ T cells and B cells, about 30% of the cells. Very few T gamma/delta and NK cells were present. The activity in terms of IL-2-R, FasL and perforin expression was low. Apoptosis of the lymphocytic cells was limited. No differences were observed between the lymphocytes in seminiferous tubules with in situ seminoma and the lymphocytes in invasive tumours. The study suggests that either specifically committed lymphocytes are not present or, if present, immune-suppressing mechanisms in addition to FasL may be working.

Methylcholanthrene-induced sarcomas in nude mice have short induction times and relatively low levels of surface MHC class I expression

In order to study the role of the T-cell-mediated immune defense in tumor development, a total of 93 sarcomas were induced using different doses (8 micrograms (0.1%), 40 micrograms (0.5%) and 400 micrograms (5%)) of 3-methylcholanthrene in athymic nude Balb/c mice and phenotypically normal immunocompetent Balb/c mice. A shorter tumor induction time and a higher tumor incidence after treatment with low doses of methylcholanthrene were seen in nude mice than in immunocompetent mice, indicating that they have a lower resistance to the carcinogen. Contrary to expectations we found that the MHC class I expression of tumors from nude mice was lower than that of tumors from normal mice. Higher surface expression of MHC class I was demonstrated on high dose tumors from normal mice than on low dose tumors from normal mice. The cellular composition of the individual tumors raised in nude mice was more heterogeneous with respect to MHC class I expression. Since the mice differ genetically only with respect to the nu gene, these results indicate that a lack of T-cell-mediated defense mechanisms may confer upon the bearer a lower resistance to 3-methylcholanthrene and a different MHC profile of the ensuing tumor.

Chemically induced sarcomas from nude mice are more immunogenic than similar sarcomas from congenic normal mice

To detect possible differences in immunogenicity between tumors induced in T cell-deficient mice and phenotypically normal congenic mice, 16 sarcomas, 8 having developed in nude BALB/c mice and 8 having developed in congenic normal (nu/+) mice, were transplanted to normal BALB/c recipients and the rates of rejection or acceptance were registered. The 16 tumors were chosen randomly from a panel of 39 sarcomas induced with 0.5% or 0.1% 3-methylcholanthrene and maintained as cell lines in culture. Out of the tumors originating from nude mice, 66% were rejected by the normal BALB/c recipients, while only 30% of the tumors originating from normal mice were rejected. Tumors with short induction times from normal mice were more readily accepted than tumors with long induction times. Tumors originating from nude mice had significantly longer mean latency times after transplantation to both normal and nude recipients than tumors originating from normal mice. Contrary to what has been reported by others, there was no correlation between the rejection rates of the individual tumors and their Kd, Dd or Ld major histocompatibility complex (MHC) class I surface expression as measured by flow cytometric analysis of cultured tumor cells. The Kd, Dd and Ld proteins of the transplanted tumor lines were analyzed by isoelectric focusing for the occurrence of mutations resulting in altered charge of the MHC protein. No such mutations were found, ruling out MHC mutations of that kind as the source of immunogenicity in the cell lines used in these experiments. Our results suggest the existence of a T cell-mediated selection in the original tumor cell mass of tumors induced in normal mice, adapting the tumor to growth in a host with a functional T cell system, but apparently there is no connection between this loss of immunogenicity and loss of MHC class I expression.

HLA class I antigens are expressed by Sertoli cells of intratubular germ cell neoplasia

Five frozen samples from seminomas and one from a combined seminoma/embryonal carcinoma and surrounding tissue were examined for the presence of HLA class I molecules using an antibody directed against a monomorphic epitope of the 45 kDa long chain of HLA-A, -B and -C molecules. Only tubules with intratubular germ cell neoplasia stained positively, while normal seminiferous tubules and invasive tumor cells stained negatively. The immunohistology with anti-HLA class I antibody was compared to that with anti-beta 2-microglobulin antibody which reacts with the light nonpolymorphic chain of all HLA class I molecules. Immunohistology with these two antibodies was indistinguishable. This result combined with immunohistology using anti-PLAP indicates that the stained cells are Sertoli cells. The results are discussed in relation to lymphocytic infiltration and immune surveillance of seminomas.

Sertoli cells of intratubular germ cell neoplasia express beta 2 microglobulin

The cells in intratubular germ cell neoplasia in the vicinity of 38 germ cell tumors of the testis, including 20 pure seminomas, were studied for the expression of beta 2-microglobulin (beta 2m), the constant component of all HLA class I molecules. Immunohistochemistry using antibodies towards beta 2m, vimentin, placental alkaline phosphatase, and ferritin was employed. Whereas the intratubular cells in normal testis are beta 2m negative, beta 2m positive cells were identified in intratubular germ cell neoplasia tubules in 55 per cent of all tumors and in 60 per cent of the seminomas. The tubules with beta 2m positive cells were located in areas with invasive tumor or in the vicinity of such areas. The beta 2m positive cells were identified as Sertoli cells by morphology and by their staining with anti-vimentin. Neoplastic germ cells, identified by morphology and staining with anti-placental alkaline phosphatase and anti-ferritin were beta 2-microglobulin negative. The most intensely beta 2m-stained Sertoli cells were found in tubules with high concentrations of neoplastic germ cells. Intensely stained Sertoli cells were also found in 'Sertoli cell only' tubules inside invasive tumors and in areas without lymphocytic infiltration. The cells in adjacent normal tubules were beta 2m negative.

Beta 2-microglobulin expression of AIDS-related and classical Kaposi's sarcoma

The expression of beta 2-microglobulin, the invariable light chain of HLA class I molecules, of Kaposi's sarcoma from 11 AIDS patients and from 11 patients without known immunodeficiency was studied by immunohistochemistry using a polyclonal antibody to beta 2-microglobulin. The staining intensity of spindle cells in these lesions was scored in a semiquantitative system. We found that the spindle cells of Kaposi's sarcomas from AIDS patients showed significantly increased staining intensity for beta 2-microglobulin compared to those of Kaposi's sarcomas from non-AIDS patients. The results may indicate that Kaposi's sarcomas developing in immunocompromised individuals, such as AIDS patients, are not subject to immune selection by T cells eliminating HLA class I high-expressing tumor cells, while this may be the case in non-AIDS patients. Alternatively, the results may be caused by differences in the activity of cytokines, which upregulate the expression of HLA class I molecules on the cell surface.

Expression of beta 2-microglobulin by premalignant epithelium

Many human tumors express low amounts of HLA class I molecules relative to the normal cells from which they are derived. From experimental work it is clear that the malignant behavior of a tumor cell may depend on its MHC class I expression. Therefore, it is of obvious interest to study the HLA class I expression of human tumors in their various stages. We have studied the HLA class I expression by the cells in premalignant epithelial lesions and invasive carcinoma of the bladder and uterine cervix using immunoperoxidase staining for beta 2-microglobulin of paraffin-embedded tissue. We here assume that beta 2-microglobulin expression by malignant and premalignant cells equals HLA class I expression. Thirty-two of the 36 invasive tumors expressed less overall beta 2-microglobulin than cells from the normal epithelium. In contrast, approximately two-thirds of 34 premalignant bladder epithelia and 47 premalignant cervix epithelia displayed higher overall beta 2-microglobulin expression than the normal epithelium. Thus, a systematic large-scale elimination of HLA class I high-expressing tumor cell variants may take place only after the tumor penetrates the basement membrane.

Tumors developing in nude mice express unusually large amounts of MHC class I antigens

Tumors were induced in athymic, T-cell-deficient nude mice and in syngeneic normal haired mice by treatment with low doses of 3-methylcholantrene (MCA). The tumors were studied for tumor cell expression of MHC class I molecules and for immunogenicity by transplantation to syngeneic haired recipients. Ten tumors were obtained by the MCA treatment, six from nude and four from haired mice. They were all fibrosarcomas as judged from their microscopic appearance. Five of the "nude" tumors expressed measurable amounts of MHC class I molecules and two of them expressed high amounts. Both were immunogenic in the sense that they evoked a cytotoxic T-cell response in transplanted haired recipients. Only one of the four "haired" tumors expressed measurable amounts of MHC class I, and none of them were immunogenic. These findings support the concept that some tumors are immunoselected at an early point of time in their existence in a host with a normal immune system and that this results in an elimination of tumor cell variants which are highly immunogenic for the T-cell system, leaving the low or non-immunogenic variants. These take over and grow and kill their host. The results suggest that tumor cell variants expressing high amounts of MHC class I are important targets in the immunoselection in hosts with a normal immune system.

Immunological status to Epstein-Barr virus and cytomegalovirus in patients with genital condylomata

Serological patterns against Epstein-Barr virus (EBV) and Cytomegalovirus (CMV) were determined in patients with genital condylomata (GC). The Ig G antibody values to EB-induced virus capsidic antigens (VCA), early antigens (EA) and Ig M to VCA were significantly higher in the study group than in the controls. Moreover, the concomitant presence of EBV-Ig G anti-VCA greater than or equal to 1/320, EBV-Ig G anti-EA greater than or equal to 1/20 and EBV-Ig M anti VCA greater than or equal to 1/20 was observed in 13 serum samples of genital condylomata patients, while, in only 2 serum samples of the healthy controls, the same serological pattern was present. The distribution of antibody values to CMV-induced LA, EA and IEA showed a significantly increased prevalence in the study group in comparison with the controls: the concomitant presence of antibody with a titre greater than or equal to 1/320 for CMV-LA, greater than or equal to 1/20 for CMV-EA and greater than or equal to 1/20 for CMV-IEA was observed in 15 serum samples of GC patients and in only 3 serum samples of the control group. Our results suggest that the active or recent EBV and CMV infections we observed in genital condylomata patients may be a consequence of impaired immunity in these patients, but it does not exclude a possible role of EBV and CMV in perpetuating human papilloma virus-induced cell proliferation.

Adenovirus proteins and MHC expression

Adenoviruses are able to specifically down-regulate the cell surface expression of MHC class I antigens. Most viral serotypes achieve these ends by synthesizing a protein that binds to class I antigens in the endoplasmic reticulum (ER) and impedes the transport of these molecules to the cell surface. However, viruses belonging to the highly oncogenic subgenus A do not affect the class I antigen expression during acute infection. Instead, they are distinct from other adenoviruses in that they specifically down-regulate the level of mRNAs, encoding MHC class I antigens, in virally transformed cells. The virus-induced reduction of class I antigen expression drastically diminishes the ability of CTLs to recognize cells infected or transformed by adenovirus. A number of issues concerning these viral mechanisms for class I antigen modulation need to be addressed. The molecular mechanism by which the E1A gene product of subgenus A viruses diminishes class I mRNA levels has not been elucidated. Also, the details of the interaction between the E19 protein and class I molecules should be studied, preferably by X-ray crystallography of the complexes. This would clarify the role of the antigen-binding site as well as other portions of the class I molecule in the binding to the E19 protein. Of general importance for our understanding of the sorting and intracellular transport of proteins is the exact delimitation of the signal for ER localization, which is present in the COOH-terminus of the E19 protein. The putative interaction of this peptide sequence with components of the ER membrane should also be studied. Finally, the study of the pathophysiological role of the MHC class I down-regulation will undoubtedly yield new insights into how the immune system combats virally infected and transformed cells.

Defective cell-mediated response to EBV-transformed B cells in a healthy individual with regular EBV antibody titers

We have analyzed the EBV-related immune parameters of a healthy EBV-seropositive individual (ST) who has regular antibody titers but defective inhibitory capacity toward the growth of autologous EBV-infected B cells. This in vitro function reflects the EBV-specific memory because it does not occur in experiments performed with cells of seronegative individuals. An analysis of events following in vitro EBV infection showed that lymphocytes of ST behaved in some tests in the same way as those collected from seronegative individuals. These parameters were: lack of gamma-IFN production 24 hr after EBV infection; low production of soluble factors that inhibit EBV-induced B-cell proliferation; lack of generation of LCL selective cytotoxicity after repeated stimulation with autologous LCL; and high proportion of EBNA-positive cells in 7-day-old EBV-infected cultures. On the other hand, cellular memory to the virus detected by the production of IL-2 24 hr after infection, and by the production of LIF upon exposure to EBV-encoded antigens, conformed with the results obtained with seropositive individuals. T-cell-mediated inhibition of EBV-induced B-cell growth in vitro has been regarded as a corollary of in vivo control of EBV-infected B cells. However, it is absent or has a low efficiency in certain disease categories which are not accompanied by risk of B-EBV growth. Our results with a healthy individual also indicate that several mechanisms contribute to a harmless life-long virus carrier state.

Natural killer cell activity and autologous mixed lymphocyte response of splenic, mesenteric lymph node, and colonic lymphocytes during DMH-induced colon carcinogenesis in the rat

Two in vitro models of immune surveillance were used to examine the immune status of the gut-associated lymphoid tissue, mesenteric lymph nodes, and spleen during the early stages of 1,2-dimethylhydrazine (DMN)-induced colon tumorigenesis. DMH- and vehicle-treated Fischer rats were sacrificed at one of three time points: one week, two months, or five months after cessation of treatment. Colonic, lymph node, and splenic natural killer cell cytolytic activity toward YAC-1 tumor targets and T-cell response to autologous Ia-induced blastogenesis were measured at each time point. We found little change in natural killer cell activity or T-cell proliferation induced by autologous Ia gene products at these time periods.

Development of antiretroviral therapy for the acquired immunodeficiency syndrome and related disorders. A progress report

We review the rationale for, and progress in, the development of antiviral therapy for the acquired immunodeficiency syndrome (AIDS). A consideration of the replicative cycle of the human immunodeficiency virus (HIV) can lead to the identification of several steps that represent potential targets for antiretroviral therapy, and several substances that can inhibit the replication of HIV in vitro have already been identified. The 2',3'-dideoxynucleosides are a class of nucleoside analogues in which the 3'-hydroxy group is modified so that it cannot form phosphodiester linkages for nucleic acid chains. Some are potent in vitro inhibitors of HIV replication, possibly acting as chain terminators of viral DNA during reverse transcription. One of these dideoxynucleoside analogues, 3'-azido-2',3'-dideoxythymidine (AZT), has now been administered for up to 18 months to patients with AIDS. The drug has been shown to improve immunologic function, to reverse, at least partially, HIV-induced neurologic dysfunction in some patients, and to improve certain other clinical abnormalities associated with AIDS. The principal toxic effect associated with AZT is dose-dependent suppression of bone marrow, resulting particularly in anemia and leukopenia; however, most patients in whom this toxic effect occurs can subsequently tolerate a lower dose of the drug. The demonstration that AZT can be beneficial in patients with AIDS has removed some of the uncertainty about the rationale for an antiretroviral intervention in HIV infection.

Astrocytoma as a second malignancy in patients with acute lymphoblastic leukemia

Three cases of astrocytoma, two cerebral (grades II and III) and one spinal (grade II) occurring as second malignancies in patients with previously diagnosed acute lymphoblastic leukemia are described. All had received prophylactic cranial irradiation and intrathecal methotrexate. All were in remission at the time of development of the second malignancy. The time interval between central nervous system (CNS) prophylaxis and symptoms of CNS tumor was between 3 and 5 years. The possible causes of the combination of astrocytoma with acute lymphoblastic leukemia are discussed.

Alterations in cytotoxic and helper T cell function after infection of T cell clones with human T cell leukemia virus, type I

HTLV-I is a transforming human retrovirus that is an etiologic agent of adult T cell leukemia/lymphoma. To investigate the effects of this virus on T cell functions, two OKT3+, OKT4+, OKT8- cytotoxic clones (8.7 and 8.8) specific for allogeneic cells bearing DPw2, a class II histocompatibility antigen, were studied before and after infection with HTLV-I. The clones retained cytotoxic function for up to 70 d after exposure to HTLV-I, even without subsequent antigenic stimulation, but then lost their cytotoxic activity. Prior to infection with HTLV-I, clone 8.8 also lysed OKT3 hybridoma cells; after infection, cytotoxic activity against these OKT3-antibody bearing cells was lost in parallel with the loss of activity against DPw2-bearing target cells. In addition, expression of T3 surface antigen by HTLV-I-infected 8.8 cells was decreased at a time when they lost their cytotoxic activity, possibly contributing to the loss of cytotoxic function. Finally, clone 8.8 could provide help for nonspecific IgG production by autologous B cells when stimulated with irradiated DPw2-bearing non-T cells. After infection with HTLV-I, this helper function became independent of DPw2-stimulation and persisted even when the cytotoxic activity was lost. An OKT4+ T cell clone thus could simultaneously manifest both cytotoxic and helper T cell activities, and these activities were differentially affected after HTLV-I infection.

Role of marrow stromal cells in the establishment of a transformed lymphoblastic B-cell line from a normal human subject

A monoclonal human B-lymphoblastoid cell line (UTMB-460) arose spontaneously from the bone marrow of a normal healthy woman who was seropositive for an EB-virus infection. Chromosomally, the UTMB-460 cells are near tetraploid, with a specific translocation (8;9) (p11.2; p24), and have surface IgMk. The UTMB-460 cells are resistant to killing in vitro by spontaneous and rIFN alpha 2 and rIL-2 stimulated NK cells from the patient and other normal subjects, but are killed by lymphokine activated killer cells. The index patient has not developed leukemia/lymphoma during the follow-up interval of 22 months. The growth of UTMB-460 cells is supported by undefined growth factors in FCS and by BCGF in the absence of FCS. rIL-2 stimulates DNA synthesis by UTMB-460 cells. The UTMB-460 cells were adherent to the normal MSC in the primary culture and show specific heterotypic adherence to normal MSC when compared to skin fibroblasts. In addition, 6/6 normal marrow stromal cells and 4/6 normal skin fibroblasts induced growth of colonies from UTMB-460 cells. These data suggest that MSC interacted with the transformed cells (UTMB-460) in vitro and played a critical role in the establishment of the UTMB-460 cell line.

Epstein-Barr virus-positive Burkitt's lymphoma cells not recognized by virus-specific T-cell surveillance

The pathogenesis of Epstein-Barr (EB) virus-positive Burkitt's lymphoma (BL) appears to involve the combined actions of virus-induced B-cell proliferation, and a rare chromosomal translocation juxtaposing c-myc and immunoglobulin gene loci in a single B cell; holoendemic malarial infection in some way facilitates the oncogenic process. Outgrowth of the EB virus-positive tumour suggests either breakdown or evasion of those immune controls, in particular cytotoxic T-cell responses against the virus-induced lymphocyte-detected membrane antigen LYDMA, which limit virus-infected B-cell numbers in healthy virus carriers. Immunosuppression, such as that which malarial infection may induce, cannot itself be a sufficient explanation in this regard since our studies have identified a number of BL patients who retain detectable LYDMA-specific T-cell surveillance. The present work shows that in many cases of virus-associated BL, the emerging malignant clone is insensitive to such surveillance. Several EB virus-positive BL cell lines, recently established in vitro and expressing the class I histocompatibility locus antigens (HLAs) which restrict cytotoxic T-cell function, were not killed by HLA-matched LYDMA-specific effector populations in assays where the EB virus-positive lymphoblastoid cell line (LCL), derived from normal B cells of the same patient, sustained high levels of lysis.

Allosensitization in tumor therapy and prophylaxis, and in female contraception--a prospect for clinical use

A hypothesis is presented on the possible role of allosensitization in therapy and prophylaxis of human tumors, and in human female contraception. The essence of the proposed treatment of human malignancies is allosensitization with allogeneic white blood cells by means of application of two blood transfusions from normal healthy donors within a certain time interval to patients with invasive or metastasizing cancer. The therapy should be accompanied by immunoglobulins, bacterial toxins and a single dose of cytostatics. In the case of a successful tumor regression a prophylaxis of recurrence should be made with two doses of intradermally injected allogeneic lympho-leucocytic concentrates mixed with bacterial toxins; such treatment might also be effective in tumor prophylaxis, or in long-lasting contraception in women. The hypothesis is supported by recent literature as well as by our recent results in the area of cell-mediated control of tissue proliferation, fetal allograft survival or tumor development. It is concluded that tumor rejection can be mediated not only by the direct effect of anti-tumor drugs but more effectively by the organisms mechanisms responsible for removal of undesirable tissue.

In vitro analysis of the Epstein-Barr virus: host balance in long-term renal allograft recipients

Four indices of the EB virus carrier state, for which quantitative in vitro assays now exist, have been monitored in 55 renal allograft recipients under long-term immunosuppression, each patient being tested on a single occasion. By comparison with parallel data from healthy control donors, the results indicate the extent to which virus replication in the throat and virus-infected B cells in the blood are increased as a result of immunosuppression; the concordance between these two independent indices of the level of EB virus infection in vivo, first noted with healthy donors, was again observed within this large group of patients. Immunosuppression also leads to an impairment of virus-specific memory T-cell responsiveness and to an increase in anti-viral antibody titres, but the results show that the level of virus infection prevailing in any one individual cannot be inferred directly from these immunological indices of the virus:host balance. In allograft patients on stable levels of immunosuppression, virus and host appear to establish a new equilibrium. Limited prospective studies suggest that the position of this new equilibrium depends critically upon the virus:host balance prevailing in the same individuals before immunosuppression began. This may be an important consideration in identifying patients for whom immunosuppression may carry a particularly high risk of developing EB virus genome-positive lymphoma.

A re-examination of the Epstein-Barr virus carrier state in healthy seropositive individuals

A panel of 24 healthy seropositive donors have been followed prospectively over a period of 15 months and monitored (1) for the level of EB virus shedding in the throat by means of a sensitive cord-blood transformation assay; (2) for the level of virus-infected B cells in the blood via a new in vitro protocol where "spontaneous transformation" can be seen to titrate against input cell number; (3) for anti-EB viral antibody titres and (4) for the prevailing level of virus-specific memory T cells in the circulation. Six donors shed easily detectable levels of EB virus into throat washings on every occasion of testing, whilst 16 other donors shed lower levels of virus detectable in throat washings on a majority (10 donors) or on a minority (6 donors) of test occasions; only 2/24 donors gave no evidence of virus shedding at any time. There was a direct relationship between the EB virus shedder status of an individual (i.e., the level of virus replication in the pharynx) and the number of infected B cells present in the circulation. These results indicate that chronic, usually low-grade, replication of the virus at some permissive site in the oro- and/or naso-pharynx is very often a stable accompaniment of the asymptomatic EB virus carrier state, and may indeed be essential for the long-term maintenance of that state.

T-cell-mediated regression of "spontaneous" and of Epstein-Barr virus-induced B-cell transformation in vitro: studies with cyclosporin A

The regression of Epstein-Barr (EB) virus-transformed B-cell outgrowth which is seen in experimentally-infected cultures of blood mononuclear (UM) cells from healthy seropositive donors can be abolished in medium containing the T-cell-suppressive agent cyclosporin A (CSA) at concentrations of 0.05 microgram/ml and above. CSA mediates its effect within the first 4 days post-infection of the UM cells and this prevents subsequent in vitro generation of the EB virus-specific cytotoxic-T-cell response which normally brings about regression. Regression can be fully restored by supplementing the CSA-treated culture with interleukin 2 (IL-2)-containing culture supernatants or indeed with purified IL-2 itself, suggesting that CSA mediates its effect in this system through inhibiting the endogenous production of IL-2 which is required to amplify the virus-specific cytotoxic response. "Spontaneous transformation" to EB virus genome-positive lymphoblastoid cell lines in noninfected cultures of UM cells from healthy seropositive donors, though rare in normal medium, is enhanced to such a degree in the presence of CSA that, for many donors, the phenomenon becomes titratable against input cell dose across the 2.0 X 10(6)-2.5 X 10(5) cells/culture range. Cell mixing experiments suggest that the spontaneously transformed cell lines which arise with such efficiency under these conditions do so not by direct in vitro outgrowth of progenitor cells transformed by the virus in vivo, but by a two-step mechanism involving virus release and secondary infection in vitro.

Cancer and normal ageing

Cancer has a monoclonal origin in a pre-mitotic cell and usually a multistep pathogenesis. The initiation of tumor development and most stages in tumor progression involve point mutations, chromosomal rearrangements, and often changes in gene dosage. Simultaneously, there is continuing selection of the cell clones most resistant to growth-regulating substances and/or lacking specific immunologic markers. Normal ageing is partly pre-programmed as demonstrated by the constancy of the maximum survival time for a species under various external conditions resulting in different mean survival times. Emerging evidence of characteristic DNA changes in post-mitotic cells of old individuals may turn out to be part of the programmed changes. However, random accumulation of mutational defects in both pre- and post-mitotic cells is an unavoidable consequence of physics and therefore contributes to normal ageing and the accompanying increase in cell diversity. Cancer incidence increases with age. Firstly, because extended exposure increases the risk of inflicting the DNA changes prerequisite to oncogenesis; secondly, because the progression from one malignant cell to detectable tumor is a matter of 10-30 per cent of a species maximum life span; and thirdly, because some alterations characteristic of normal ageing increase the susceptibility to carcinogens. There probably is an overlap of etiologic/accelerating factors for cancer and ageing. Such aspects of normal ageing such as decline in DNA repair capacity and decline in cellular immune reactivity should facilitate induction and early growth of neoplasia. Age changes that counteract cancer development include (hormonal) loss of proliferative stimulation and depletion of the pool of immature cells at greatest risk.

Tumorigenicity of cells transformed by adenovirus type 12 by evasion of T-cell immunity

Evidence is presented that cells transformed by adenovirus type 12 are oncogenic because they escape from T-cell immunity. This effect is brought about by reducing the expression of class I transplantation antigens and is a function of the protein translated from the 13S mRNA, transcribed from early region 1a. These findings establish a novel mechanism by which transformed cells can acquire an oncogenic phenotype.

Necrotizing pseudolymphomatous lymphadenitis and rapidly fatal lymphoma in Okinawa

Thirty-one cases of a peculiar lymphadenitis with pathognomonic necrosis and prominent infiltration with immunoblasts were studied together with 36 cases of a rapidly fatal lymphoma of distinctive morphological pattern and characterized by massive coagulative necrosis. These cases all occurred on the island of Okinawa, and the lesions have not, to our knowledge, been reported previously. This further example of a type of geographically confined lymph nodal disease may, on further study yield insights into pathogenetic mechanisms in lymphomas. Further studies should include cell marker and virological investigations, which were not available to us at the time of the study.

Immunology of metastasis. Can the immune response cope with disseminated tumor?

The application of immunologic methods to the treatment of neoplasia has been a goal of research in tumor immunology. Unfortunately, no clearly defined success for such therapy has been achieved. However, the most recent advances in tumor biology have provided for a more valid conceptual framework upon which to plan further research in this area. The more general awareness of tumor progression and heterogeneity, particularly in the context of tumor metastasis, while imposing a sense of gloom regarding all therapeutic modalities, shifted immunologic thinking toward the development of nonspecific modalities. We herein propose that this 'shift' may be premature and that immunotherapy using cytolygic T cells could still be feasible. Our views are based on newer approaches for selecting immunogenic variants of malignant tumors and a better understanding of the relationship of the immune response to metastases.

Interaction of Epstein-Barr virus with leukaemic B cells in vitro. II. Cell line establishment from prolymphocytic leukaemia and from Waldenström's macroglobulinaemia

Leukaemic B-cell populations were prepared from six patients with high-count prolymphocytic leukaemia (PLL) as well as from one patient with Waldenström's macroglobulinaemia (WM) in frankly leukaemic phase, and their response to in vitro Epstein-Barr (EB) virus infection was monitored in terms of expression of the virus-associated nuclear antigen EBNA and of virus-induced transformation to continuous cell lines. The individual leukaemic populations, tested on several occasions, gave reproducibly different responses one from another which were not obviously related to differences either of surface immunoglobulin phenotype or of immunoglobulin secretor status in vivo. After infection, four out of six PLL populations showed either transient or a more persistent expression of EBNA, always involving a minority of the cells, with no evidence of any virus-induced transformation up to six weeks. In contrast, two out of six PLL samples as well as the WM sample rapidly gave rise to EBNA-positive cell lines which, on the evidence both of restricted immunoglobulin class expression and of abnormal marker chromosomes, were clearly derived from the leukaemic cells. Further comparative studies of such leukaemic B-cell populations may help to define host cell components necessary for the triggering of EB-virus-induced cellular transformation.

Epstein-Barr virus-induced diseases in boys with the X-linked lymphoproliferative syndrome (XLP): update on studies of the registry

Analyses of 100 subjects with the X-linked lymphoproliferative syndrome (XLP) in 25 kindreds revealed four major interrelated phenotypes: infectious mononucleosis, malignant B-cell lymphoma, aplastic anemia, and hypogammaglobulinemia. Eighty-one of the patients died. Two male subjects were asymptomatic but showed immunodeficiency to Epstein-Barr virus (EBV). Seventy-five subjects had the infectious mononucleosis phenotype and concurrently, 17 subjects of this group had aplastic anemia. All subjects with aplastic anemia died within a week. Aplastic anemia did not accompany hypogammaglobulinemia or malignant lymphoma phenotypes. Hypogammaglobulinemia had been detected before infectious mononucleosis in three subjects, after infectious mononucleosis in five subjects, and was not associated with infectious mononucleosis in 11 boys with hypogammaglobulinemia. In nine subjects infectious mononucleosis appeared to have evolved into malignant lymphoma; however, the majority of patients with malignant lymphoma showed no obvious antecedent infectious mononucleosis. One subject had infectious mononucleosis following recurrent malignant lymphoma. Twenty-six of 35 lymphomas were in the terminal ileum. Results of immunologic and virologic studies of 15 survivors revealed combined variable immunodeficiency and deficient antibody responses to EBV-specific antigens. Mothers of boys with XLP exhibited abnormally elevated titers of antibodies of EBV. Subjects of both sexes with phenotypes of XLP should be investigated for immunodeficiency to EBV. Persons with inherited or acquired immunodeficiency may be vulnerable to life-threatening EBV-induced diseases.

Fetal and oncofetal antigens - regulators of immune reactions

This paper proposes the hypothesis that cells which express fetal antigen activate a variety of suppressor mechanisms and thus induce a state of immunological tolerance. Clinical and experimental evidence is cited which supports the hypothesis and indicates that foreign antigens, expressed in association with fetal antigen, are actively tolerated. Thus the fetus, which bears foreign histocompatibility antigens and neoplastic tumours which re-express fetal antigens, fail to evoke appropriate immunological rejection responses, but rather induce a state of active tolerance.

Emerging immunologic approaches to treatment of neoplastic diseases

Recent research on the immunobiology of the tumor-host relationship has demonstrated that nonspecific cellular immune reactions, like natural killer cells and cytotoxic autoreactive cells, may be far more potent antineoplastic mechanisms than specific T lymphocyte cytotoxicity. The hybridoma technique, making it possible to raise monoclonal antibodies against predefined antigens, has rendered passive immunotherapy more attractive. It is suggested that the combination of nonspecific cellular immune reactions with monoclonal antibodies may be a highly efficient antineoplastic therapy for minimal residual disease.

Natural killer cell activity in a population of leukemia-prone wild mice (Mus musculus)

Natural cell-mediated cytotoxicity against YAC-I targets was measured in splenocytes from leukemia-prone wild mice trapped near Lake Casitas (LC) in southern California. Cytotoxicity was mediated by cells that were non-adherent to nylon wool, non-phagocytic and resistant to thy-1.2 antiserum plus complement. Natural MuLV viremia in LC mice did not impair splenic cytotoxicity against TAC-I target cells, Cells infected with amphotropic and ecotropic MuLV of wild mouse origin were not appreciably lysed by LC splenic effectors. Although variable levels of cytotoxicity were detected against TAC-1 by normal spleen cells, consistently low levels of cytotoxicity against allogenic LC lymphoma, sarcoma and carcinoma targets were found using the same splenocytes. These results indicate that LC mice possess splenocytes with the characteristics of natural killer (NK) cells as defined in inbred mice. The resistance of LC-derived targets to lysis by LC NK cells suggests that NK cells may not be involved in natural tumor immunosurveillance or that the development of spontaneous tumors may involve escape from NK-mediated effector mechanisms.

Cytogenetic studies on African Burkitt's lymphoma cell lines: t(8;14), t(2;8) and t(8;22) translocations

Cytogenetic studies on ten African Epstein-Barr virus (EBV) positive Burkitt's lymphoma (BL) cell lines were performed. The usual translocation t(8;14) (q24;q32) was found in five of them, a deletion del(8) (q24 leads to qter) in another one, while four variants were observed, two of these having a t(2;8) (p12;q24) translocation and two a t(8;22) (q24;q11) translocation. Other chromosome abnormalities were seen in seven of the cell lines, but these varied from one cell line to another. Thus, variant translocations, such as we describe here, are found in endemic BL cases. Two of these variants are identical to those previously identified in BL from nonendemic areas. The common chromosome abnormality of these BL cell lines was a rearrangement of the 8q24 band. The role of this constant cytogenetic change remains to be elucidated.