[Myelodysplastic syndrome developed in a mother and her son whose bone marrow karyotype showed monosomy 7]

Two familial cases of myelodysplastic syndrome (MDS) are reported, one of whom had an abnormal karyotype of 45, XY, -7 (monosomy 7). Case 1 was a 60-year-old woman developed dizziness and nasal bleeding. She was treated with blood transfusion alone. About 11 months after diagnosis, she died of pneumonia. Case 2 was a 22 year-old man, who was the son of case 1, developed febrile disease because of recurrent skin and oral mucosa infections. He had a partial response to low-dose of cytarabine. Thirteen months after diagnosis, he died of severe pneumonia. Both cases were diagnosed as having refractory anemia with excess of blasts due to peripheral blood and bone marrow findings. Both patients had pancytopenia, erythroid hyperplasia in bone marrow, marked dyserythropoiesis, recurrent infectious diseases and severe pneumonia that resulted in death. These symptoms resembled to those reported for monosomy 7 syndrome. Familial MDS with monosomy 7 is rarely reported. These cases are of interest to investigate hereditary factors of MDS.

Expression of CD10/neutral endopeptidase in normal and malignant tissues of the human stomach and colon

The expression of common acute lymphoblastic leukemia antigen (CALLA; CD10), which is identical to neutral endopeptidase (NEP, EC3.424.11), was examined in the malignant and adjacent noninvaded tissues of the human stomach and colon (n = 27). All of 27 normal and 18 well or moderately differentiated adenocarcioma tissue specimens were positive for monoclonal antibody (mAb) NL-1 against CD10/NEP, whereas the expression level was clearly decreased in all of 9 specimens of poorly differentiated adenocarcinoma. In addition, all of 7 gastric or colorectal carcinoma cell lines tested showed decreased expression of CD10/NEP. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis of the crude antigen J5 from the normal colon tissue lysate by mAb J5 detected a single band of approximately 100 kDa that was consistent with that of NALM-6 cells used as a positive control. These findings suggest that CD10/NEP is expressed in normal epithelial cells of the human stomach and colon, whereas the expression level is decreased in the poorly differentiated type of adenocarcinoma.

Prognostic significance of abnormal p53 accumulation in primary, resected non-small-cell lung cancers

PURPOSE

This study was conducted to evaluate the prognostic significance of p53 abnormalities in primary, resected non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Methodologic validation of immunohistologic detection of p53 abnormalities in routine pathology sections was assessed using 31 lung cancer specimens for which p53 gene status was known from our previous molecular biologic studies. Applying the optimized cutoff value, we evaluated the prognostic significance of p53 abnormalities in an independent cohort of 208 NSCLC patients with complete follow-up data, whose resections were consecutively performed between January 1984 and December 1988.

RESULTS

Immunohistologic detection of p53 abnormalities appeared to be reliable and showed approximately 90% concordance with the p53 gene status. Using the selected cutoff value of 10%, 46% of 208 NSCLCs showed p53 abnormalities. There was no relationship between p53 abnormalities and clinical outcome in the entire cohort, which represented all histologic subtypes of NSCLC (P = .58). Based on the reasoning that the influence of p53 abnormalities may have been obscured by distinct biologic roles depending on histologic subtypes, we also separately analyzed subsets of patients with adenocarcinomas (n = 100) and with squamous cell carcinomas (n = 88) and found that it may be a useful prognosticator only in adenocarcinoma patients (P = .04).

CONCLUSION

p53 abnormalities are not a significant prognostic factor in primary, resected NSCLC when all histologic subtypes are combined, but may be a useful prognosticator for adenocarcinomas. Additional studies are warranted for further evaluation, specifically of adenocarcinomas.

Effect of jinkoh-eremol and agarospirol from agarwood on the central nervous system in mice

Agarwood (Jinkoh in Japanese), one of the Oriental medicines, is used as a sedative. The benzene extract of this medicine showed a prolonged effect on the hexobarbital-induced sleeping time, and hypothermic effects in terms of rectal temperature, a suppressive effect on acetic acid-writhing, and a reduction of the spontaneous motility in mice. By repeated fractionation, oral administration in mice, and pharmacological screening, the active principles, jinkoh-eremol and agarospirol, were obtained from the benzene extract. They also gave positive effects on the central nervous system by peritoneal and intracerebroventricular administration. They decreased both methamphetamine- and apomorphine-induced spontaneous motility. The level of homovanillic acid in the brain was increased by them, while the levels of monoamines and other metabolites were unchanged. Similar results were seen in chlorpromazine-administered mice. Therefore, jinkoh-eremol and agarospirol can be considered to be neuroleptic.

Modification of chemo-radiosensitivity of a human lung cancer cell line by introduction of the glutathione S-transferase pi gene

Recent studies have suggested that glutathione S-transferase pi (GST-pi) may play a role in determining tumor sensitivities to cytotoxic drugs. In order to better understand the role of this enzyme in chemo- and/or radioresistance of lung cancer cells, we examined whether introduction of GST-pi cDNA into a chemo- and radiosensitive lung cancer cell line altered its sensitivities to various chemotherapeutic agents and/or ionizing radiation, which are often used in the management of lung cancers. Modestly increased resistance of the GST-pi transfectants preferentially to sublethal damage caused by ionizing radiation as well as to adriamycin (ADM) was observed. In contrast, resistances to cisplatin (CDDP), etoposide (VP-16), irinotecan hydrochloride (CPT-11) and paclitaxel were virtually unaltered. These results suggest that GST-pi may not play a major role in chemo- and radioresistance of lung cancers, although it could afford selective and limited protection against ADM- and ionizing radiation-induced damage.

Inconsistent association of Epstein-Barr virus with CD56 (NCAM)-positive angiocentric lymphoma occuring in sites other than the upper and lower respiratory tract

We previously described nine cases of angiocentric lymphoma of a possible natural killer (NK)-cell lineage with a surface CD3-CD56+ phenotype occurring in sites other than the upper and lower respiratory tract. This study was performed to investigate the association of Epstein-Barr virus (EBV) with these lymphomas, using the polymerase chain reaction (PCR) for the presence of EBV-DNA, in situ hybridization (ISH) for EBV-encoded small RNAs (EBERs) and immunohistology for EBV-determined nuclear antigen-2 (EBNA-2) and latent membrane protein-1 (LMP-1) in paraffin sections. PCR and ISH produced almost identical results, and EBERs were identified in the nuclei of the lymphoma cells of three cases, two of which exhibited LMP-1 in the cytoplasm of tumour cells without EBNA-2 expression. Molecular genetic analysis revealed EBV to be incorporated into these three EBER-positive cases either clonally or biclonally. It was revealed by re-evaluation of their morphology with the established EBV status on each case that, in contrast to the rather variable and irregular cellular composition of the EBV-positive tumours, the EBV-negative tumours stood out because of their remarkably uniform 'blastoid' appearance, and could be grouped as blastic NK-cell lymphoma. The relationship of the EBV-positive cases with nasal NK-cell tumours has yet to be clarified.

Cloning and expression of a murine cDNA homologous to the human RCK/P54, a lymphoma-linked chromosomal translocation junction gene on 11q23

The RCK/P54 gene was previously isolated from the chromosome translocation breakpoint region on 11q23 of a human lymphoma cell line, RC-K8, with t(11;14)(q23;q32). It was found to encode a 472-483-amino-acid (aa) polypeptide belonging to an RNA helicase/translation initiation factor family. The aim of the present investigation was the isolation and comparative sequence analysis of the mouse RCK/P54 cDNA from a BALB/c spleen cDNA library. Sequence analysis revealed an open reading frame (ORF) predicting a polypeptide of 483 aa showing 97.7% identity to human RCK/p54. Northern analysis demonstrated a 7.5-kb signal in all tissues tested and in vitro translation analysis showed a 54-kDa polypeptide. These results indicate that both mouse and human RCK/P54 are highly conserved.

Angioimmunoblastic T-cell lymphoma (angioimmunoblastic lymphadenopathy with dysproteinemia [AILD]-type T-cell lymphoma) followed by Hodgkin's disease associated with Epstein-Barr virus

A patient is described with angioimmunoblastic T-cell lymphoma (AIL) (angioimmunoblastic lymphadenopathy with dysproteinemia [AILD]-type T-cell lymphoma), which was later followed by Hodgkin's disease. At the time of the initial diagnosis, histological examination of a cervical lymph node showed a typical picture of AIL with abundant clear cells which were CD45RO+, CD43+, and CD20-, and there was no evidence of a monoclonal B-cell proliferation by immunohistochemical analysis. In situ hybridization for Epstein-Barr virus (EBV) was negative. Interposed by a bout of recurrence, the patient developed, 16 years later, a left subparotid mass which showed histologic features of Hodgkin's disease, mixed cellularity type. Diagnostic Reed-Sternberg cells and their variants were CD30+, CD15- and CD20+. Neither rearrangement of TCR beta and gamma chain genes nor of immunoglobulin heavy chain and kappa light chain genes was detected in DNA extract from fresh material. In situ hybridization showed the presence of EBV within the Reed-Sternberg cells. The data show that EBV was not etiologically related to AIL in this case. Further, the deficit in cellular immunity that accompanied AIL conceivably permit primary EBV infection or reactivation of latent infection, which eventuated in development of Hodgkin's disease, but the exact pathogenesis remains uncertain.

Ki-1 (CD30) positive anaplastic large cell lymphoma of T-cell phenotype developing in association with long-standing tuberculous pyothorax: report of a case with detection of Epstein-Barr virus genome in the tumor cells

We report a case of CD30 positive anaplastic large cell lymphoma of T-cell phenotype developing in association with long-standing tuberculous pyothorax. Phenotypic analysis showed CD1a-, CD2+, CD3+, CD4+, CD5-, CD8-, CD10-, CD19-, CD20 +/-, CD21-, CD25-, CD56-, T-cell receptor (TCR) alpha/beta antigens-, and HLA-DR+ phenotype. Neither rearrangement of TCR beta and gamma chain genes or of immunoglobulin heavy chain gene was detected in DNA extract from fresh material. The lymphoma cells were also shown to express the latent membrane protein-1 and the Epstein-Barr virus (EBV)-encoded nuclear antigen-2 by immunohistochemistry and EBV-encoded small RNAs by in situ hybridization.

[Molecular approach to lung cancer]

Lung cancer is associated with a number of cytogenetic abnormalities, such as chromosomal deletions on 3p, 12q, and 17p, which suggest the involvement of multiple tumor suppressor genes. These findings led to the discovery of the inactivation of the Rb and p53 genes in lung cancer. Recent remarkable progress in molecular biology should add a number of genes to the list of tumor suppressor gene involved in the pathogenesis of lung cancer. In addition, dominant oncogenes as well growth factors and their receptors have been shown to be involved in this process. Our understanding of the molecular pathogenesis of this fatal disease will now allow us to design new strategies to better diagnose and treat lung cancer. In this symposium, we discuss how the molecular oncological approach can be used to reduce the rapidly increasing rates of death due to lung cancer.

Distinct mutational spectrum of the p53 gene in lung cancers from Chinese women in Hong Kong

Accumulating evidence suggests that the p53 gene is a good target for molecular epidemiological studies to search for risk factors in carcinogenic events. The lung cancer incidence for females in Hong Kong is unusually high, ranking among the highest in the world despite a low percentage with a history of smoking. To gain insights into possible etiological risk factors responsible for this high incidence, we examined p53 mutations in 35 lung cancer specimens from Chinese females living in Hong Kong and compared them with 35 matched cases from Japanese women as well as previously reported p53 mutations in the world literature. p53 mutations in exons 5-8 were present in 20 and 31% of the Hong Kong and Japanese cases, respectively. Notably, single-base deletions within runs of identical bases were observed in 3 (43%) of the 7 mutations in the Hong Kong cases, in contrast to the absence of such mutations in the controls and the extreme scarcity in the literature, suggesting that distinct environmental and/or genetic factor(s) might be involved. Although the frequent occurrence of characteristic single-base deletions could be a reflection of mutator mutations leading to inefficient mismatch repair of slipped strand mispairings, none of the lung cancer specimens exhibited such microsatellite instabilities.

Differential expression of the c-kit proto-oncogene in germ cell tumours

The c-kit proto-oncogene product and its ligand stem cell factor play an important role in haematopoiesis, spermatogenesis, and melanogenesis. Using an anti-c-kit antiserum raised against a synthetic peptide, we studied the immunohistochemical expression of the c-kit gene product in 60 germ cell tumours (GCTs) (53 testicular, 7 extragonadal), derived from primary GCTs in 45 cases and metastatic tumours in 15 cases. Twenty-eight out of 28 seminomas showed c-kit membranous staining in the majority of cells. A similar pattern of expression was seen in intratubular germ cell neoplasia. Nine out of 29 (32 per cent) non-seminomas displayed cytoplasmic, but not membranous, c-kit immunoreactivity in occasional cells. In three mixed GCTs, c-kit expression was limited to the seminoma component. In normal testis, c-kit expression was observed in some basal tubular cells, corresponding to undifferentiated spermatogonia. These results suggest a role for c-kit in the oncogenesis of GCT, where down-regulation of c-kit might be a critical step during progression from seminomas to non-seminomas. Immunohistochemical analysis of c-kit should be considered as a diagnostic aid for GCT and in particular may be helpful in the identification of certain extragonadal seminomas.

Effect of α-santalol and β-santalol from sandalwood on the central nervous system in mice

Sandalwood (Byakudan in Japanese; Santalum album L.) is used as a popular sedative in Oriental medicine. Extracts of the wood of Santalum album were obtained by successively extracting with benzene, chloroform, methanol and water. Each of these fractions was tested for activity on the central nervous system of mice following intraperitoneal administration, i.e. potentiation of hexobarbital sleeping time, body temperature alterations, antinociceptive and spontaneous motor activity changes. The benzene extract was active in these assays and was then separated further into fractions 1, 2 and 3. Fraction 2 was shown to be the most active in the aforementioned assays, α- and β-Santalols were isolated from this active fraction as the major CNS active constituents. They were both active by the intragastric and intracerebroventricular routes of administration. Thus, it can be considered that α- and β-santalols contribute to the reputed sedative effect of sandalwood preparations in Oriental medicine. Additionally, α- and β-santalols significantly increased the levels of homovanillic acid, 3,4-dihydroxyphenylacetic acid and/or 5-hydroxyindoleacetic acid in the brain of mice, and chlorpromazine did the ones of homovanillic acid and 3,4-dihydroxyphenylacetic acid. These results showed that α- and β-santalols could be considered as neuroleptic by resemblance to the pharmacological activities of chlorpromazine.

The positive nuclear staining observed with monoclonal antibody against PRAD1/cyclin D1 correlates with mRNA expression in mantle cell lymphoma

Recently, we produced a monoclonal antibody, 5D4, against the PRAD1/cyclin D1 product and suggested positive nuclear staining to be associated with mantle cell lymphoma (MCL). Now we have further characterized the specificity of this antibody and studied the relation of immunohistochemical detection to PRAD1/cyclin D1 mRNA expression and DNA rearrangement. Immunofluorescence and immunoblotting studies demonstrated the 5D4 antibody to be crossreactive with cyclin D2, but not cyclin D3. On immunostaining, 15 of 19 MCL cases (79%) presented the nuclear staining pattern and PRAD1/cyclin D1 mRNA expression was detected by Northern blot analysis in 12 of 15 MCL cases studied (80%): all cases with the mRNA expression showed the nuclear staining pattern. Southern blot analysis with 11q13 BCL-1 probes detected DNA rearrangements in 8 of 19 MCL cases (42%), all 8 exhibiting PRAD1/cyclin D1 mRNA expression. In 21 lymphoma cases of types other than MCL, neither the mRNA expression nor the nuclear staining were observed, although cytoplasmic staining was often apparent. These results indicated that positive nuclear staining of lymphoma cells by 5D4 antibody reflects PRAD1/cyclin D1 mRNA expression, and showed that this monoclonal antibody has diagnostic value for differentiating MCL from other types of lymphomas.

Detection of hydroxyl radical in intact cells of Chlorella vulgaris

Using ESR with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trapping reagent, we measured the levels of free radical species generated from living cells of Chlorella vulgaris var. vulgails (IAM C-534). To investigate the production of free radicals in the living Chlorella vulgaris cells, the influence of DMPO toward the intact cells of the Chlorella vulgaris using the O2 evolution rate was first studied as a guide. Since the O2 evolution rate was not changed by DMPO, it was judged that DMPO has no toxicity toward the intact cells of Chlorella vulgaris. Only hydroxyl radicals (.OH) were detected as the DMPO-OH adduct in the suspension of intact cells of Chlorella vulgaris irradiated with visible light. Moreover, since production of .OH was inhibited by some hydroxyl radical scavengers such as KI and ethanol, production of .OH was proved to be due to hydroxyl radicals. It was also clear that the intensity of .OH increased with increasing irradiation intensity of visible light. Therefore, it was suggested that .OH might be one of the photoinhibition factors of the intact Chlorella vulgaris cells in severe light conditions.

Elevated expression of Unph, a proto-oncogene at 3p21.3, in human lung tumors

The murine Unp proto-oncogene encodes a nuclear ubiquitin protease whose overexpression leads to oncogenic transformation of NIH3T3 cells. We have cloned cDNAs originating from the human homolog of this gene, designated herein as Unph (Unp, human), and have used these cDNAs to map the gene to 3p21.3, a region frequently rearranged in human tumor cells. Unph mRNA levels are consistently elevated in small cell tumors and adenocarcinomas of the lung, suggesting a possible causative role for the gene in the neoplastic process.

A 130 kDa polypeptide immunologically related to the 180 kDa catalytic subunit of DNA polymerase alpha-primase complex is detected in early embryos of Drosophila

An immunocytochemical method using specific antibodies was employed to detect DNA polymerase alpha-primase complex in Drosophila melanogaster embryos during the first 13 nuclear division cycles. A monoclonal antibody specific to the 72 kDa polypeptide stained interphase nuclei, but not metaphase chromosome, while at late anaphase and thereafter staining of the chromosome was regained. On the other hand, a polyclonal antibody specific to the 180 kDa polypeptide stained not only the interphase nuclei but also the cytoplasmic regions surrounding interphase nuclei. These results suggest that the distributions of the 180 kDa and the 72 kDa polypeptides of DNA polymerase alpha-primase complex are different. We detected the 180 kDa and the 72 kDa polypeptides in the extract prepared from a single Drosophila embryo by Western blotting, and a 130 kDa polypeptide immunologically related to the 180 kDa polypeptide was also detected in the extract. These polypeptides (180, 130, and 72 kDa) in the embryos were detected at similar levels at interphase and at the mitotic phase. These three polypeptides were also detected in unfertilized eggs, showing that they were maternally stored. The 130 kDa polypeptide was detected till cycle 10, then began to decrease, and finally disappeared at cycle 14, whereas the 180 kDa and the 72 kDa polypeptides were present without marked fluctuation in quantity throughout the developmental stages. Even in unfertilized eggs, the level of the 130 kDa polypeptide decreased gradually with a similar time course to that in fertilized ones, but the levels of the 180 kDa and the 72 kDa polypeptides remained unchanged. This is the first report suggesting the existence of the 130 kDa polypeptide in vivo in the early embryos of Drosophila. The significance of the 130 kDa polypeptide is discussed.

Frequent loss of imprinting of the H19 gene is often associated with its overexpression in human lung cancers

Accumulating evidence suggests that deregulation of the insulin-like growth factor II (IGF2) and H19 genes at 11p15, due to loss of imprinting (LOI), plays a role in the oncogenesis of Wilms' tumors. We previously reported LOI of IGF2 in carcinomas of the lung, a common cancer of adults. We show here that LOI of H19 is also a frequent event in lung cancer development, and correlated with hypomethylation of the promoter region. Furthermore, the present study also revealed that overexpression of H19 is often associated with LOI of H19 in lung cancers retaining both parental alleles, showing a contrast to LOI in Wilms' tumors. Interestingly, in contrast to frequent LOI of the imprinted genes at 11p15, LOI was not observed for the remaining gene known to be imprinted in man, SNRPN at 15q12.

canoe encodes a novel protein containing a GLGF/DHR motif and functions with Notch and scabrous in common developmental pathways in Drosophila

The canoemisty1 (cnomis1) mutation was isolated by virtue of its severe rough eye phenotype from approximately 500 fly lines, each harboring a single autosomal insertion of a P element (Bm delta w). Excision of the P element generated a lethal, null allele, cnomis10, together with many revertants with normal eye morphology. Ommatidia homozygous for cnomis10, produced in an otherwise wild-type eye by somatic recombination, typically contain a reduced number of outer photoreceptors. Some cnomis1 homozygous adults bear extra macrochaetes on the head, notum, humerus and/or scutellum. cnomis1 hemizygotes often show conspicuous wing phenotypes such as a notched blade and the loss of a cross vein. The sequence of cno cDNA clones isolated from an embryonic cDNA library revealed a long open reading frame that potentially encodes a 1893-amino-acid protein with the GLGF/DHR motif, a conserved sequence in Discs large, Dishevelled, and some other proteins associated with cellular junctions. Flies doubly mutant for cnomis1 and scabrous1 (sca1) and those for cnomis1 and the split (spl) allele of Notch (N) always have rumpled wings curved downward. The spl; cnomis1 double mutant flies also exhibit a "giant socket" phenotype. These phenotypes are rarely observed flies singly mutant for either cnomis1, sca1 or spl. The wing vein gaps caused by Abruptex1, a N allele producing an activated form of N protein, are dominantly suppressed by cnomis1. Heterozygosity for shaggy and myospheroid promotes formation of extra wing veins in cnomis1 homozygotes. The genetic interactions suggest that cno participates with members of the N pathway in regulating adhesive cell-cell interactions for the determination of cell fate.

In vivo occurrence of p16 (MTS1) and p15 (MTS2) alterations preferentially in non-small cell lung cancers

Frequent homozygous deletions of the p16 (MTS1) gene encoding a cyclin-dependent kinase inhibitor were recently reported in various tumor cell lines including examples derived from lung cancers, but direct evidence for their occurrence in lung cancer patients has not been reported thus far. In the present study, alterations of p16 and/or p15, a p16-related cyclin-dependent kinase, were observed not only in lung cancer cell lines but also in the corresponding tumor specimens in vivo, excluding the possibility of in vitro artifacts. Interestingly, a clear specificity was also noted in terms of the affected histological subtype; i.e., only non-small cell lung cancers carried alterations (6 of 20 as compared to 0 of 20 small cell lung cancer cell lines).

Bispecific antibody-mediated cytotoxicity by CD4+ and CD8(+)-activated T cells generated from leukemia patients after allogeneic bone marrow transplantation

The F(ab')2 bispecific antibody (BSAb) was prepared from anti-CD3 moAb and anti-CD10 moAb. The BSAb could react with both CD3+ T cells and CD10+ leukemia cells and triggered T cell-mediated cytotoxicity. To apply the BSAb to prevention of leukemic relapse after BMT, we investigated the generation of both CD4+ and CD8+ anti-tumor effector T cells from patient's PBMC 14 days after BMT. Neither CD4+ T cells nor CD8+ T cells, which were activated with immobilized anti-CD3 moAb plus IL-2, could lyse CD10+ leukemia cells by themselves, but they showed augmented cytotoxicity against CD10+ leukemia cells by targeting with anti-CD3 x anti-CD10 BSAb. Moreover, the activated CD4+ T cells were demonstrated to produce IL-2 and IFN-gamma when they were cultured with CD10+ leukemia cells in the presence of the BSAb. The BSAb-mediated cytotoxicity of activated T cells was demonstrated not only against the recipient leukemia cells but also against third party leukemia cells. These results suggested that anti-CD3 x anti-CD10 BSAb might be a good tool to prevent relapse after BMT in combination with activated CD4+ T cells and CD8+ T cells.

Phenotypic and molecular characterization of croaker, a new mating behavior mutant of Drosophila melanogaster

Mating of Drosophila melanogaster is a stereotypically patterned behavior consisting of a fixed sequence of actions that is primarily under genetic control. Although courtship can be easily monitored and quantified, little is known about its neural basis. To obtain a better understanding of cellular and molecular mechanisms underlying courtship, we have isolated mutants that disrupt specific aspects of mating behavior. The croaker mutant was isolated from approximately 1,000 lines harboring single P-element insertions by screening for aberrant courtship song: croaker males often generate polycyclic pulse song while most of the song pulses are monocyclic in the wild-type. The mutant is also defective in flight. Intracellular recordings of excitatory junction potentials from larval body wall muscles and Ca++ action potentials from adult indirect flight muscles demonstrated that neuromuscular transmission and Ca++ electrogenesis in the muscle fibers are not impaired by the croaker mutation. To define the croaker gene molecularly, genomic DNA surrounding the P-element insertion site was cloned by plasmid rescue and subsequent screening of a cosmid library. Northern blotting with the genomic DNA probes detected three transcripts in the wild-type, which were not expressed in the croaker mutant.

Immune function in mice lacking the perforin gene

Mice lacking the perforin gene were generated by using targeted gene disruption in embryonal stem cells. When infected with lymphocytic choriomeningitis virus (LCMV), perforin-less (-/-) mice showed clear signs of having mounted an immune response based on activation of CD8 T cells but were unable to clear the LCMV infection. This failure to eliminate virus was accompanied by a failure to generate spleen cells capable of lysing LCMV-infected fibroblasts in vitro. Spleen cells from LCMV-infected -/- mice were able to lyse hematopoietic target cells after exposure to phorbol 12-myristate 13-acetate and ionomycin, provided the target cells expressed the Fas antigen. Spleen cells from -/- mice also responded to alloantigen in mixed leukocyte culture by blastogenesis and proliferation. The resulting cells were able to lyse hematopoietic target cells, although not as well as spleen cells from +/+ littermates sensitized in the same manner. However, lysis by -/- cells was again seen only if the target cells expressed Fas antigen. We conclude that perforin-less -/- mice retain and express the Fas lytic pathway as expressed in vitro but that this pathway is insufficient to clear an LCMV infection in vivo.