Deciphering cell states and genealogies of human haematopoiesis

The human blood system is maintained through the differentiation and massive amplification of a limited number of long-lived haematopoietic stem cells (HSCs)1. Perturbations to this process underlie diverse diseases, but the clonal contributions to human haematopoiesis and how this changes with age remain incompletely understood. Although recent insights have emerged from barcoding studies in model systems2-5, simultaneous detection of cell states and phylogenies from natural barcodes in humans remains challenging. Here we introduce an improved, single-cell lineage-tracing system based on deep detection of naturally occurring mitochondrial DNA mutations with simultaneous readout of transcriptional states and chromatin accessibility. We use this system to define the clonal architecture of HSCs and map the physiological state and output of clones. We uncover functional heterogeneity in HSC clones, which is stable over months and manifests as both differences in total HSC output and biases towards the production of different mature cell types. We also find that the diversity of HSC clones decreases markedly with age, leading to an oligoclonal structure with multiple distinct clonal expansions. Our study thus provides a clonally resolved and cell-state-aware atlas of human haematopoiesis at single-cell resolution, showing an unappreciated functional diversity of human HSC clones and, more broadly, paving the way for refined studies of clonal dynamics across a range of tissues in human health and disease.

Somatic mutations and cell identity linked by Genotyping of Transcriptomes

Defining the transcriptomic identity of malignant cells is challenging in the absence of surface markers that distinguish cancer clones from one another, or from admixed non-neoplastic cells. To address this challenge, here we developed Genotyping of Transcriptomes (GoT), a method to integrate genotyping with high-throughput droplet-based single-cell RNA sequencing. We apply GoT to profile 38,290 CD34+ cells from patients with CALR-mutated myeloproliferative neoplasms to study how somatic mutations corrupt the complex process of human haematopoiesis. High-resolution mapping of malignant versus normal haematopoietic progenitors revealed an increasing fitness advantage with myeloid differentiation of cells with mutated CALR. We identified the unfolded protein response as a predominant outcome of CALR mutations, with a considerable dependency on cell identity, as well as upregulation of the NF-κB pathway specifically in uncommitted stem cells. We further extended the GoT toolkit to genotype multiple targets and loci that are distant from transcript ends. Together, these findings reveal that the transcriptional output of somatic mutations in myeloproliferative neoplasms is dependent on the native cell identity.

Protein expression from synthetic genes: Selection of clones using GFP

Construction of synthetic genes is today the most elegant way to optimize the heterologous expression of a recombinant protein. However, the selection of positive clones that incorporate the correct synthetic DNA fragments is a bottleneck as current methods of gene synthesis introduce 3.5 nucleotide deletions per kb. Furthermore, even when all predictable optimizations for protein production have been introduced into the synthetic gene, production of the protein is often disappointing: protein is produced in too low amounts or end up in inclusion bodies. We propose a strategy to overcome these two problems simultaneously by cloning the synthetic gene upstream of a reporter gene. This permits the selection of clones devoid of frame-shift mutations. In addition, beside nucleotide deletion, an average of three non-neutral mutations per kb are introduced during gene synthesis. Using a reporter protein downstream of the synthetic gene, allows the selection of clones with random mutations improving the expression or the folding of the protein of interest. The problem of errors found in synthetic genes is then turned into an advantage since it provides polymorphism useful for molecular evolution. The use of synthetic genes appears as an alternative to the error-prone PCR strategy to generate the variations necessary in protein engineering experiments.

Emergence and spread of two distinct clonal groups of multidrug-resistant Escherichia coli in a veterinary teaching hospital in Australia

Multidrug-resistant Escherichia coli (MDREC) expressing AmpC β-lactamases have emerged as a cause of opportunistic infections in dogs. Following a cluster of extraintestinal infections caused by two distinct clonal groups (CGs) of bla CMY-producing MDREC, a 12-month infection control study was undertaken at a veterinary teaching hospital in Brisbane, Australia. Swabs from the rectum of hospitalized dogs (n=780), hospital staff (n=16) and the hospital environment (n=220) were plated onto selective agar to obtain multidrug-resistant (MDR) coliforms. These were then tested by multiplex PCR for E. coli uspA, bla CMY and the class 1 integron-associated dfrA17-aadA5 gene cassette for rapid identification of MDREC CG 1 (positive for all three genes) and CG 2 (positive for uspA and bla CMY only). A total of 16.5 % of the dog rectal swabs and 4.1 % of the hospital environmental swabs yielded MDREC, and on the basis of multiplex PCR, PFGE and plasmid profiling, these were confirmed to belong to either CG 1 or CG 2. Both CG 1 and CG 2 isolates were obtained from clinical cases of extraintestinal infection and rectal swabs from hospitalized dogs over the same period of time, whereas only CG 1 isolates were obtained from the hospital environment. Both CGs were prevalent during the first 6 months, but only CG 2 was isolated during the second 6 months of the study. Two isolates obtained from rectal swabs of staff working in the hospital belonged to CG 2, with one of the isolates possessing the same REDP as nine isolates from dogs, including six isolates associated with cases of extraintestinal infection. CG 1 isolates belonged to E. coli serotypes O162 : H−, OR : H− or Ont : H−, whereas CG 2 isolates belonged to O153 : HR, OR : HR or OR : H34. These results confirm that in this particular outbreak, canine MDREC were highly clonal and CG 2 MDREC may colonize both humans and dogs.

Variation in Trypanosoma cruzi clonal composition detected in blood patients and xenodiagnosis triatomines: implications in the molecular epidemiology of Chile

To identify Trypanosoma cruzi clones from chronically infected individuals, they were transferred to triatomines by the xenodiagnosis test (XD) with Triatoma infestans. Polymerase chain reaction (PCR) and hybridization assays were performed to detect minicircle DNA in human blood samples and triatomine feces, using probes to determine the T. cruzi clones present. T. cruzi clone 19 (TcI) resulted the most prevalent in humans, with a frequency of 0.70 compared with a frequency of 0.53 in triatomines. T. cruzi clone 39 (TcIId) was the most prevalent in T. infestans, with a frequency of 0.65 compared with 0.33 in humans. The T. cruzi clone 43 (TcIIe) was not detected in blood samples; nevertheless, it was present at a rate of 0.17 in T. infestans feces. In conclusion, the T. cruzi clones are associated to each host, suggesting that selective amplification of clones occurs in human and triatomines.

Clonal and Capsular Types Decide Whether Pneumococci Will Act as a Primary or Opportunistic Pathogen

BACKGROUND

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. The role of the different capsular and clonal types in invasive disease severity remains to be defined.

METHODS

Disease severity and disease type were correlated to age, underlying disease, capsular serotype, and clonal type of the causative agent for 494 adult patients with invasive pneumococcal disease.

RESULTS

Pneumococcal isolates of serotypes 1 and 7F were genetically homogenous, had the highest potential to infect previously healthy individuals, and were not causing deaths. Also, type 1 isolates were only found among younger adults, whereas other serotypes were mainly found among elderly persons (e.g., type 23F). Some serotypes and/or clones were more prone to cause more-severe disease, as observed by high APACHE II scores calculated at admission, and were also associated with a high mortality (e.g., clones of type 3 and 11A). We found no evidence of an impact of penicillin resistance on disease severity and disease type.

CONCLUSIONS

We suggest that clones with capsular types 1 and 7F, which are known to have a high invasive disease potential, behave as primary pathogens, whereas clones with other capsular types with a lower relative risk of causing invasive disease are more opportunistic, primarily affecting patients with underlying disease. Disease caused by the latter group, however, was more severe, even in previously healthy individuals.

Spermatogonial stem cells: questions, models and perspectives

This review looks into the phylogeny of spermatogonial stem cells and describes their basic biological features. We are focusing on species-specific differences of spermatogonial stem cell physiology. We propose revised models for the clonal expansion of spermatogonia and for the potential existence of true stem cells and progenitors in primates but not in rodents. We create a new model for the species-specific arrangements of spermatogenic stages which may depend on the variable clonal expansion patterns. We also provide a brief overview of germ cell transplantation as a powerful tool for basic research and its potential use in a clinical setting.

The hematopoietic stem compartment consists of a limited number of discrete stem cell subsets

Hematopoietic stem cells (HSCs) display extensive heterogeneity in their behavior even when isolated as phenotypically homogeneous populations. It is not clear whether this heterogeneity reflects inherently diverse subsets of HSCs or a homogeneous population of HSCs diversified by their response to different external stimuli. To address this, we analyzed 97 individual HSCs in long-term transplantation assays. HSC clones were obtained from unseparated bone marrow (BM) through limiting dilution approaches. Following transplantation into individual hosts, donor-type cells in blood were measured bimonthly and the resulting repopulation kinetics were grouped according to overall shape. Only 16 types of repopulation kinetics were found among the HSC clones even though combinatorially 54 groups were possible. All HSC clones, regardless of their origin, could be assigned to this subset of groups, and the probability of finding new patterns is negligible. Thus, the full repertoire of repopulating HSCs was covered. These data indicate that the HSC compartment consists of a limited number of distinct HSC subsets, each with predictable behavior. Enrichment of HSCs (Lin- Rho- SP) changes the representation of HSC types by selecting for distinct subsets of HSCs. These data from the steady-state HSC repertoire could provide a basis for the diagnosis of perturbed patterns of HSCs potentially caused by disease or aging.

Analysis of T-cell clonality pattern in tumor samples of breast cancer patients

PURPOSE AND METHODS

A large body of experimental evidence has confirmed that different tumors, including breast carcinomas, can stimulate specific T-cell-mediated immune responses. In this study we have analyzed patterns of T-cell clonality in tumor samples of 54 breast cancer patients classified as lymph node negative, N0 (n=16), or lymph node positive, N+ (n=38). The clonality of T-cells was analyzed by the PCR-PAGE method.

RESULTS

Monoclonal/oligoclonal (M/O) T-cell populations were found in 15 breast cancer patients, nine N+ and six N0. In all analyzed groups (N+ + N0, N+, N0) the incidence of relapse was not significantly different between patients with M/O and patients with polyclonal T-cells. Comparison of disease-free interval (DFI) between patients divided according to the presence of TCRgamma monoclonality/oligoclonality showed a marginally significant difference only in the group of N+ patients within the first 24 months of follow-up. Patients with a M/O T-cell population had a shorter DFI than patients with a polyclonal T-cell population. This difference was not observed when the complete follow-up period was considered in the same group of patients. Furthermore, there was no significant difference in overall survival (OS) between patients with M/O and patients with polyclonal T-cells.

CONCLUSION

Our results imply that tumor infiltrating T-cells are usually polyclonal. The pattern of T-cell clonality does not correlate with the incidence of relapse and the duration of DFI and OS in the analyzed groups of breast cancer patients, excluding N+ patients with M/O T-cells who had a shorter DFI in the first 24 months of follow-up. This observation suggests that polyclonal T-cell populations may provide a broader spectrum of T-cell-mediated antitumor response.

Usefulness of Cutaneous T-Cell Clonality Analysis for the Diagnosis of Cutaneous T-Cell Lymphoma in Patients With Erythroderma

Context.—Demonstration of a dominant T-cell clone in skin biopsy specimens by a molecular assay constitutes an additional diagnostic criterion to differentiate cutaneous T-cell lymphomas (CTCLs) from inflammatory dermatoses.

Objective.—To determine which patients, depending on their clinical presentations, could most benefit from a cutaneous T-cell clonality analysis in addition to histopathologic analysis for the diagnosis of CTCL.

Design.—Comparison of sensitivity and specificity of histopathologic analysis and a combination of this method and the detection of a T-cell receptor γ chain gene rearrangement by polymerase chain reaction denaturing gradient gel electrophoresis performed on skin biopsy specimens obtained at initial presentation.

Patients.—One hundred forty consecutive patients were classified into 4 groups, depending on their clinical presentation: (1) eczematous patches suggestive of early-stage mycosis fungoides (MF) (IA and IB of the TNM classification) (n = 42); (2) plaques, nodules, or tumors that arise on or are associated with plaques suggestive of late-stage MF (IIB and III of the TNM classification) (n = 16); (3) erythroderma (n = 50); and (4) nodules or tumors that arise in normal skin, suggestive of non-MF CTCL (n = 32).

Results.—When compared with histopathologic examination, the addition of clonality analysis increased the sensitivity of CTCL diagnosis in all groups of patients except those with cutaneous lesions suggestive of late-stage MF, because the diagnosis was made based on histopathologic analysis alone in 100% of these cases. The main increase in sensitivity of CTCL diagnosis was observed in patients with erythroderma: 62% with histopathologic analysis alone to 87% with the combination of both methods (P = .04). Diagnostic specificity of molecular assays decreased from 100% to 76% (P = .01) in patients with patch lesions and from 100% to 70% (P = .04) in patients with nodules that occurred in normal skin due to the detection of a T-cell clone in 6 patients with follicular mucinosis without a histologic pattern of MF and in 5 of 20 cases of T-cell pseudolymphoma (25%), respectively. In contrast, a T-cell clone was not detected in the 34 patients with erythroderma of inflammatory origin.

Conclusion.—Polymerase chain reaction analysis of cutaneous T-cell clonality could be useful for the diagnosis of CTCL in patients who present with erythroderma.

Variations of Porphyromonas gingivalis fimbriae in relation to microbial pathogenesis

OBJECTIVES

Periodontal disease is an infectious disorder caused by a small subset of periodontal pathogens including Porphyromonas gingivalis. Accumulated evidences show that the expression of P. gingivalis heterogenic virulence properties is dependent on its clonal diversity. P. gingivalis expresses two distinct fimbria molecules, major and minor fimbriae, on its cell surfaces, both of which seem to be involved in the development of periodontitis. In this short review, variations of fimbriae in relation to microbial pathogenesis are discussed.

MATERIALS AND METHODS

Our recent findings are summarized to elucidate the relationship between clonal variation of fimbriae and bacterial pathogenicity of various strains.

RESULTS

Major fimbriae were classified into six types (I to V and Ib) based on the diversity of fimA genes encoding FimA (a subunit of major fimbriae). A majority of periodontitis patients were found to carry type II fimA organisms, followed by type IV, and type II fimA organisms were significantly occurred with more severe forms of periodontitis. Studies of clones with type II fimA have revealed significantly greater adhesive and invasive capabilities to epithelial cells than other fimA type clones. Minor fimbriae induced interleukin-1alpha (IL-1alpha), IL-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) cytokine expression in macrophages and were suggested to be a causative factor of alveolar bone resorption in animal models. The clonal diversity of minor fimbriae is unclear, however, distinct minor fimbria molecules were found in different strains.

CONCLUSION

The fimbria variations may have an influence on the development of periodontal disease.

A noninvasive genetic/pharmacologic strategy for visualizing cell morphology and clonal relationships in the mouse

Analysis of cellular morphology is the most general approach to neuronal classification. With the increased use of genetically engineered mice, there is a growing need for methods that can selectively visualize the morphologies of specified subsets of neurons. This capability is needed both to define cell morphologic phenotypes and to mark cells in a noninvasive manner for lineage studies. To this end, we describe a bipartite genetic system based on a Cre-estrogen receptor (ER) fusion protein that irreversibly activates a plasma membrane-bound alkaline phosphatase reporter gene by site-specific recombination. Because the efficiency and timing of gene rearrangement is controlled pharmacologically, a sparse subset of labeled cells can be generated from the set of CreER-expressing cells at any time during development. Histochemical visualization of alkaline phosphatase activity reveals neuronal morphology with strong and uniform labeling of all processes.

Multipotential stem cells in adult mouse gastric epithelium

Previous studies of chimeric animals demonstrate that multipotential stem cells play a role in the development of the gastric epithelium; however, despite much effort, it is not clear whether they persist into adulthood. Here, chemical mutagenesis was used to label random epithelial cells by loss of transgene function in adult hemizygous ROSA26 mice, a mouse strain expressing the transgene lacZ in all tissues. Many clones derived from such cells contained all the major epithelial cell types, thereby demonstrating existence of functional multipotential stem cells in adult mouse gastric epithelium. We also observed clones containing only a single mature cell type, indicating the presence of long-lived committed progenitors in the gastric epithelium. Similar results were obtained in duodenum and colon, showing that this mouse model is suitable for lineage tracing in all regions of the gastrointestinal tract and likely useful for cell lineage studies in other adult renewing tissues.

Polymerase chain reaction-based clonality analysis in thyroid lymphoma

A previous patho-epidemiological study indicated that thyroid lymphoma (TL) evolves among active lymphoid cells into chronic lymphocytic thyroiditis (CLTH), a thyroid-specific autoimmune disease. In this study, clonality of B-cells in the CLTH and TL lesions was analyzed using polymerase chain reaction (PCR)-based method on surgically resected samples from 10 cases of TL; 7 mucosa-associated lymphoid tissue (MALT) lymphoma and 3 diffuse large B-cell lymphoma (DLBCL). CLTH lesions coexisted in all the cases with MALT lymphoma, but not in the three DLBCL cases. In cases of MALT lymphoma, the lymphomatous and CLTH areas were separately microdissected from each section and analyzed for clonality. In the cases of DLBCL, the whole specimens were used for clonality analysis. CLTH lesions showed smear in 6 samples, two bands in one, and more than three (oligoclonal pattern) in 2. MALT lymphoma lesions showed single or two bands (monoclonal pattern) in 4, oligoclonal pattern in 4, and smear in one. DLBCL showed monoclonal pattern in two and oligoclonal pattern in one. One common band was present among two separate MALT lesions in one case, but no common bands were found in the remaining six cases. These findings suggested the clonal evolution of B-cell from polyclonal to monoclonal proliferation to take place in the continuum of lymphoproliferative lesions into autoimmune thyroiditis.

Multipotent neural stem cells reside into the rostral extension and olfactory bulb of adult rodents

The lateral walls of the forebrain lateral ventricles are the richest source of stem cells in the adult mammalian brain. These stem cells give rise to new olfactory neurons that are renewed throughout life. The neurons originate in the subventricular zone (SVZ), migrate within the rostral extension (RE) of the SVZ along the rostral migratory stream (RMS) within tube-like structures formed of glial cells, to eventually reach the olfactory bulb (OB). We demonstrate that, contrary to the current view, multipotential (neuronal-astroglial-oligodendroglial) precursors with stem cell features can be isolated not only from the SVZ but also from the entire RE, including the distal portion within the OB. Specifically, these stem cells do not derive from the migratory neuroblasts coming from the SVZ. Interestingly, stem cells isolated from the proximal RE generate significantly more oligodendrocytes, and those from the distal RE proliferate significantly more slowly than stem cells derived from the SVZ and other RE regions. These findings demonstrate that stem cells are not confined to the forebrain periventricular region and indicate that stem cells endowed with different functional characteristics occur at different levels of the SVZ-RE pathway.

When does a clone deserve a name? A perspective on bacterial species based on population genetics

Molecular population-genetic analysis has revealed that for several human diseases, including tuberculosis, plague and shigellosis, the generally accepted taxonomic status of the organisms involved does not fit the usually accepted genus or species criteria. This raises the question of what species concept to apply to bacteria. We suggest that the species definition in bacteria should be based on analysis of sequence variation in housekeeping genes, and also that the "clone" be given official status in bacterial nomenclature. This will allow demotion of the species or genus status of several traditionally recognized human pathogens, but retention of current names of anomalous species and genera as clone names.

Relationship between the ability to support differentiation of osteoclast-like cells and adipogenesis in murine stromal cells derived from bone marrow

In vitro osteoclast differentiation is supported by stromal cells. In order to isolate a stromal cell line that can support osteoclast differentiation, 22 cell lines were cloned from mouse bone marrow. One of these clones, TMS-14, is a line of preadipocytes that supports osteoclast-like cell formation without any bone resorbing factors; and another, TMS-12, is a line of preosteoblasts that supports osteoclast-like cell formation with bone resorbing factors such as prostaglandin E(2)(PGE(2)). The difference of these two lines for osteoclast formation was not related with their abilities of PGE(2)production, but with the expression of osteoclast differentiation factor (ODF, also called OPGL, RANKL, and TRANCE), which detected with RT-PCR, in both cell lines. In TMS-14 cells, ODF mRNA was detected with or without PGE(2). In TMS-12 cells, ODF expression was detected in the PGE(2)-treated cells alone. When TMS-14 cells were induced to undergo adipogenic differentiation in response to treatment with thiazolidinedione, a ligand and activator of peroxisome proliferator-activated receptor gamma (PPARgamma), the ability of TMS-14 cells to support osteoclast-like cell formation was prevented in the presence or absence of 1,25(OH)(2)D(3). The gene expression of ODF in TMS-14 cells was also inhibited by treatment with thiazolidinedione. These results suggest that adipogenesis in bone marrow cells is related to the ability to support osteoclast differentiation. This is the first report of a cloned stromal cell line that can support osteoclastogenesis without the treatment with any osteotropic factors. Furthermore, this murine clonal preadipose cell line may be useful for studying senescence-dependent osteoporosis.

Persistence of oral colonization by the same Actinobacillus actinomycetemcomitans strain(s)

BACKGROUND

The Gram-negative facultatively anaerobic coccobacillus Actinobacillus actinomycetemcomitans is the major pathogen in localized juvenile periodontitis (LJP) and some forms of adult periodontitis (AP). A. actinomycetemcomitans can be grouped into 5 serotypes (a through e) based on differences in the carbohydrate moiety of cell surface lipopolysaccharide. The A. actinomycetemcomitans population is genetically heterogeneous. Since the studies on A. actinomycetemcomitans colonization have mostly applied only culture techniques, the clonality of the follow-up isolates has not been established. Thus, it is possible that, although A. actinomycetemcomitans could be repeatedly isolated from an individual, the initial colonizing strain was replaced by another strain. The aim of the study was to determine whether oral A. actinomycetemcomitans strains change spontaneously over time or after periodontal treatment.

METHODS

A total of 922 A. actinomycetemcomitans isolates were recovered from 115 subjects. From each subject A. actinomycetemcomitans isolates were obtained from 2 to 9 follow-up samples 0.5 to 11.5 years apart. After the first sampling occasion, 99 subjects were treated for either LJP or AP, whereas the 16 non-periodontitis subjects received no treatment. All A. actinomycetemcomitans isolates were serotyped and 235 isolates from 52 subjects genotyped with AP-PCR and/or with ribotyping.

RESULTS

Isolates of only one serotype, or non-serotypeable isolates alone, were repeatedly found in 104 subjects; serotype a occurred in 25%, b in 33%, c in 23%, d in 5%, e in 7%, and non-serotypeable isolates in 8% of these subjects. Two serotypes (or serotypeable isolates together with non-serotypeable isolates) occurred simultaneously in 9 subjects and in each of these subjects at least one of the serotypes was detected at each sampling occasion. In one subject the initial serotype reappeared although a different serotype was once seen alone, whereas in another subject the initial serotype could not be recovered later. Identical genotypes of A. actinomycetemcomitans were repeatedly detected in each of 52 subjects with follow-up isolates of the same serotype.

CONCLUSIONS

The results showed that spontaneous or treatment-induced change in the oral A. actinomycetemcomitans strain(s) is extremely rare and that colonization with the same strain(s) seems to be remarkably persistent.

Novel target antigens of the variant-specific immune response to Plasmodium falciparum identified by differential screening of an expression library

A primary infection by the Plasmodium falciparum Palo Alto O and R antigenic variants induces a variant-specific immunity in the Saimiri sciureus monkey. We have shown that these variants express distinct PfEMP1 antigens and differ in their levels of expression of additional antigens, including two conserved erythrocyte membrane-associated proteins, HRP1 and PfEMP3. To identify the antigens eliciting a variant-specific response, we conducted a differential screening of a lambdagt11 library with variant-specific sera. We report here the analysis of the 46 anti-R-specific clones. Two specific targets of the anti-R response were identified: (i) PfEMP3, suggesting that immunogenicity of this antigen is modulated by its relative abundance in different variants, and (ii) Asn-rich motifs. Most anti-R-specific clones, derived from so-far-undescribed genes, were detected by a cross-reaction on poly(Asn) stretches, as indicated by elimination of the signal after absorption on Asn-rich sequences. Reverse transcription-PCR (RT-PCR) showed that expression of the gene defined by clone 13 was R specific. Pepscan analysis of clone 13 identified three Asn-rich polypeptides and one unique peptide reacting specifically with antibodies eluted from the R-infected erythrocyte surface. Antisera raised to the unique peptide reacted with an R-specific protein. Attempts to demonstrate that clone 13 was derived from a var gene by using PCRs combining clone 13 and var-derived primers were unsuccessful. The var genes expressed by O and R parasites were identified not by this strategy but by RT-PCR with var-specific primers. This work has provided novel insights into immunity to antigenic variants and has identified a novel gene switched on during antigenic variation.

Frequent clonal expansion of peripheral T cells in patients with autoimmune diseases: a novel detecting system possibly applicable to laboratory examination

To investigate T cell involvement in antigen-specific immune responses, it is important to detect accumulating T cells at a clonal level in vivo. However, thus far the clinical application of such analyses has been limited. Here we have established novel primers to anneal with T cell receptor (TCR) beta genes of multiple Vbeta families and applied them to reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis to evaluate peripheral T cell clonality of autoimmune disease patients. As a result, the new Vbeta primers could detect accumulating T cell clones in the periphery of healthy individuals and patients. It was revealed that patients with autoimmune diseases such as systemic lupus erythematosus (SLE) had a larger number of clonal accumulations of peripheral T cells compared with normal individuals. Thus, the RT-PCR-SSCP system using the new multifamily Vbeta primers is the first such laboratory examination to detect T cell clonal expansion, and will provide a simple and sensitive tool to aid in the diagnosis and also in the investigation of the pathogenesis of autoimmune diseases.

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy was studied in a five-month period in 1996, during which all S. aureus isolated were collected. All MRSA isolates (95) and a sample of methicillin-susceptible S. aureus (20) were typed with a variety of phenotypic and genotypic methods. Clonal identities were determined by pulsed-field gel electrophoresis (PFGE) of chromosomal SmaI digests and, for MRSA isolates, by probing ClaI digests with a mecA probe and a Tn554 probe. Overall, MRSA represented 32.3% of all isolates, with very high percentages from the intensive care units (adult and neonatal). PFGE after restriction with SmaI resolved genomic DNA of 95 MRSA strains into 26 major PFGE patterns. The use of southern blot hybridization of ClaI genomic digests with mecA and Tn554 allowed us a significant increase in discrimination, differentiating at least 32 different clones. Two major clones, however, each sharing common ClaI-mecA and Tn554 type and PFGE pattern as well as a common resistance phenotype, represented more than 50% of all MRSA isolates. The recovery of these two clones in the majority of the isolates of adult and neonatal intensive care units, respectively, is indicative of typical nosocomial outbreaks and clonal spread. It is concluded that intensive care units are major areas requiring preventative interventions.

Double-target fluorescence in situ hybridization distinguishes multiple genetically aberrant clones in head and neck squamous cell carcinoma

Genomic heterogeneity has been observed in several solid tumor types. To investigate this phenomenon in head and neck squamous cell carcinoma (HNSCC), we analyzed macroscopically distinct tissue samples of 12 resected tumors by a combination of fluorescence in situ hybridization (FISH) and DNA flow cytometry. Using a panel of centromeric DNA probes, numerical chromosomal aberrations were detected in 10 tumors, 9 of which showed a single DNA aneuploid peak. Imbalances in chromosomal copy numbers resulted in unique patterns of chromosomal aberrations for each tumor case. Two types of tumors could be distinguished, i.e., tumors (n = 5) containing a single aneusomic clone and tumors (n = 5) with multiple aneusomic clones. The center of this latter group of tumors was shown to be genetically more heterogeneous than the tumor margin. In conclusion, this study showed that 1) the pattern of chromosomal aberrations varies greatly between different HNSCC, 2) a major clone with a specific pattern of chromosomal aberrations has spread throughout most HNSCC, and 3) a subgroup of HNSCCs contains additional clones with a different pattern of chromosomal aberrations. Based on these results, HNSCC can be divided into a genetically more homogeneous and a genetically more heterogeneous group.

Clonal analysis by ribotyping of Fusobacterium nucleatum isolates obtained from healthy young adults with optimal plaque control

Fusobacterium nucleatum is a Gram-negative anaerobic rod implicated in the pathogenesis of periodontal disease. However, this organism has also been frequently identified in high numbers in healthy adults. These observations suggest that the species may comprise different clonal types, some of which may participate in disease. The purpose of the present investigation was to use restriction endonuclease analysis (REA) and ribotyping to characterize F. nucleatum clonal types isolated from healthy young adults with optimal plaque control and investigate the stability of some of these clonal types. A group comprising 11 dental students and 11 dental outpatients with optimal plaque control was sampled. Clonal stability was investigated by sampling the dental student group at baseline and at 16 months. One hundred and thirty-two clinical isolates of F. nucleatum were successfully recovered from 15/22 individuals. For the positive subjects, 29 different clonal types were identified by REA and ribotyping, each subject and site being colonized by 1-4 clonal types. For the dental students, 9 and 15 different clonal types were identified at baseline and 16 months, respectively. None of the students harboured identical clonal types at both sampling times. Our results show that ribotyping is a useful technique for monitoring the distributions of F. nucleatum clonal types and indicate that healthy individuals with optimal plaque control can be colonized by more than one F. nucleatum clonal type and that these clonal types appear to be unstable.

Fetal mouse NK cell clones are deficient in Ly49 expression, share a common broad lytic specificity, and undergo continuous and extensive diversification in vitro

NK cells obtained by exposing mouse fetal thymocytes to appropriate combinations of IL-4, IL-2, and PMA are phenotypically indistinguishable from cultured adult splenic NK cells with the exception that they generally lack measurable expression of all of the inhibitory Ly49 molecules that can currently be detected with Abs (Ly49A, -C, -G, and -I) and of the activating molecule Ly49D. Despite this deficiency, fetal NK cells have a similar specificity to Ly49-expressing adult splenic NK cells. Individual fetal NK cell clones display an essentially invariant and broad specificity similar to that of polyclonal populations of fetal or adult NK cells, although significant differences in the fine specificity of clones can occasionally be detected. Most remarkably, cloned fetal NK cell lines display heterogeneous expression of a restricted set of surface molecules that includes 10A7, Ly6C, 3C2, CD8, certain isoforms of CD45, and also, occasionally, Ly49 molecules. This heterogeneity is not related to the cell cycle or activation status of the cells, and micromanipulation recloning demonstrates unambiguously that it is not due to a lack of a single cell origin. Diversity is generated rapidly and the capacity for diversification appears to persist indefinitely in vitro. The expression of individual variable Ags is independent and stochastic, resulting in fetal NK "clones" being potentially composed of hundreds of phenotypically distinct cells. We hypothesize that fetal NK cells behave as progenitor cells that are undergoing a process of rapid, extensive, and continuous diversification and that are individually capable of generating and regenerating a complex NK cell repertoire.

Pulsed-field gel electrophoresis analysis of clonal relationships among Neisseria meningitidis A strains from different outbreaks

Pulsed-field gel electrophoresis was used to analyze the DNA of 67 Neisseria meningitidis A strains from five African outbreaks occurring between 1988 and 1996. Endonuclease Bg/II was used to cut chromosomal DNA, generating 19 analyzable fragments. This technique allowed comparison of clonal relationships between outbreak strains and revealed that the same pulsotype was responsible for the outbreaks. This pulsotype is closely related to strain B54, subgroup III reference strain, Finland, 1975, showing only two fragment differences.

IL-2 receptor expression in autoimmune MRL-lpr/lpr mice. The expanded L3T4-, Lyt-2- population does not express p75 and cannot generate functional high-affinity IL-2 receptors

Autoimmune MRL-lpr/lpr mice develop an SLE-like disease characterized by a profound lymphadenopathy within an L3T4-, Lyt-2- (DN), B220+ T-cell population. Despite its immature phenotype this subset expresses mature alpha beta TCR belonging predominantly to the V beta 8 gene family and appears to be identical to an activated form of a minor T cell population present in both the thymus and periphery of normal mice. However, the mechanisms underlying the greatly increased cellularity in lpr/lpr-bearing mice are not understood. In this study, the IL-2R expression of lpr/lpr T cells was examined to assess the contribution of IL-2-mediated division to their expansion. The lpr/lpr DN T cells lacked high-affinity IL-2R, even after stimulation, suggesting that IL-2-dependent proliferation plays no role in the expansion of these cells and demonstrating the existence of this unusual T cell phenotype in vivo.

Differential antigen presentation by cloned populations of mouse splenic macrophages

Soft agar colonies of mouse splenic macrophages differ in their ability to process and present complex Ag to T cell hybridomas. To determine if the basis for this differential activity was the synthesis of molecules that might interfere with the activity of either the hybridoma or the indicator cells used for the bioassay of IL-2, culture supernatants were compared from Ag-presenting and nonpresenting cultures for their content of suppressor activity, using mitogen-treated mouse SC. No correlation was found between a colony's Ag-presenting activity and its secretion of suppressor factors, nor did colonies unable to present Ag release factors that interfered with the detection of IL-2. In a second approach, paired subcultures from individual colonies were tested for their ability to present, to the same hybridoma, both native Ag and the "preprocessed" peptide of the Ag. The presentation of native Ag was restricted to the progeny of a minority of the cloned macrophage progenitors, but all of the progeny cultures presented the peptide. Together, these results suggest that the basis for differential Ag presentation may be in the manner in which the cloned macrophages degrade and process ingested Ag.

OKT4 monoclonal antibody-induced activation of an autoreactive T-cell clone

We report the presence of a CD4-mediated T-cell activation pathway on an autoreactive CD3+WT31+CD4+CD8- T-cell clone, designated 2F9, isolated from the peripheral blood of a patient with ovarian adenocarcinoma. The OKT4 mab modulated the CD4 antigen independently of the CD3 antigen or the alpha beta T-cell receptor. OKT4 mab immobilized on plastic or soluble OKT4 mab in the presence of feeder PBMC induced proliferation and IL-2 production by cells of the 2F9 clone. Mixtures of the OKT4 mab and the OKT3 or anti-WT31 mabs induced additive proliferative responses and IL-2 production. The OKT4 mab synergized with recombinant IL-2 in inducing proliferative responses. These results suggest the presence of activation pathway on 2F9 cells.

CD4+ cytolytic T cell clones restricted to HLA class II, DR beta I, and DR beta III chains

We have investigated the functional polymorphism of HLA class II antigens using CD4+ CTL clones. Seven CD4+ CTL clones were isolated from a healthy donor (HLA A2 A24; B8 B27; DRw17 DRw52a) by repeated stimulation with irradiated autologous EBV-transformed B cell lines (EBV-B). According to the HLA restriction specificity we divided CD4+ CTL clones into three subgroups: (i) DRw17-restricted CD4+ CTL clones; (ii) DRw52a-restricted CD4+ CTL clones; and (iii) the CD4+ CTL clones, of which the restriction specificity could not be assigned to products of a single HLA locus. Interestingly, DRw17-restricted CD4+ CTL clones distinguished between DRw17 and DRw18. Similarly, DRw52a-restricted CD4+ CTL clones distinguished between DRw52a, w52b, and w52c. There are four amino acids which differ between DRw17 and DRw18, whereas five differ between DRw52a and the other two alleles (DRw52b and DRw52c). The recent elucidation of the crystal structure of a human class I MHC molecule has identified the probable peptide binding site to be a cleft on the outer surface of the molecule, between two alpha-helices. On the basis of the theoretical model for HLA class II molecules, amino acid positions 26 and 28 (DRw17 vs DRw18) and amino acid positions 26, 28, and 74 (DRw52a vs the other two alleles) lie within the "cleft." We propose that amino acid positions 26 and 28 are very important sites with regard to the recognition of antigen-MHC complex by the TCR.

Accessory cell function of Th2 clones

We have investigated the ability of T helper clones to serve as accessory cells and in the presence of mitogen activate freshly-isolated, splenic T cells. In this type of costimulatory assay, the Th cells that secrete IL-4 but not the Th cells that secrete IL-2 function as AC to induce T cell proliferation in the presence of various T cell mitogens (Con A, anti-CD3 mAb, anti-TCR mAb, and anti-Thy-1 mAb). The signal provided by the accessory Th2 cells occurred independently of MHC restriction, and the analysis of dose-response curves showed the involvement of a single stimulator cell. CD4, as well as CD8 expressing splenic T cells were induced to proliferate by the Th2 clones and mitogen, but mAb specific for CD4 or CD8 failed to affect the response. These findings indicate that cloned Th2 cells functioned as accessory cells and induced naive T cells to proliferate in the presence of mitogen.

Mapping of epitopes recognized by alloreactive cytotoxic T lymphocytes using inhibition by MHC peptides

To identify epitopes recognized by alloreactive CTL we have examined H-2Kb-specific CTL for their recognition of synthetic peptides with sequences derived from the native Kb class I molecule. Consecutive nested peptides spanning the immunogenic alpha 1 and alpha 2 domains of Kb were tested for their capacity to inhibit CTL clones in their recognition of cells expressing the native Kb molecule. Inhibition by these peptides was found to be an extremely rare event. One peptide (Kb.111-122) did inhibit recognition by one particular CTL clone, clone 13. Upon further investigation it was observed that clone 13 also recognized peptide Kb.111-122 when presented in the context of the syngeneic MHC molecule, Kd. Considering that residues 111 to 122 are located at the base of the antigen groove, and clone 13 is able to recognize Kb.111-122 when presented by syngeneic target cells, we suggest that inhibition of this CTL clone may be due to MHC restricted, self-presentation of peptide rather than to direct binding of free peptide to the TCR. Taken together, these results suggest inhibition of allospecific CTL by MHC peptides is a rare event at least for Kb recognition. Furthermore, they demonstrate the need for caution when interpreting inhibition by peptide as evidence for recognition by the TCR of the corresponding region on the native molecule.

Membrane IgD and membrane IgM differ in capacity to transduce inhibitory signals within the same human B cell clonal populations

The relative capacity of two coexpressed membrane Ig (mIg) isotypes, mIgM and mIgD, to actively transduce tolerogenic signals was evaluated with three human B cell leukemic clonal populations. Although anti-IgM mAb directed to various domains of the mIgM molecule suppressed spontaneous or T cell factor-induced leukemic DNA synthesis at concentrations as low as 0.01 to 0.1 microgram/ml, anti-IgD antibodies of both monoclonal and polyclonal origin failed to inhibit at doses as high as 100 micrograms/ml. Several possibilities for the differential capacity of mIgM and mIgD molecules to signal inhibition in these leukemic clonal populations were evaluated. Differences in the intrinsic membrane expression of the two isotypes before in vitro clonal activation were not responsible because the above distinctions were noted in cells of a chronic lymphocytic leukemia, which expressed slightly more mIgD than mIgM. The ineffective inhibitory signaling capacity of mIgD-specific ligands was also not caused by a selective decrease in the membrane expression of mIgD during cell culture, because the density of each isotype remained relatively constant during the first 44 h of in vitro activation by T cell factors, and following capping, mIgM and mIgD were resynthesized with similar kinetics. Because anti-IgM and anti-IgD mAb with comparable affinities for their respective membrane molecules differed significantly in inhibitory potential, it was considered improbable that the IgD-specific ligands tested bound to mIgD with a suboptimal affinity for inducing tolerance. Inhibition of leukemic DNA synthesis was observed after incubation with either anti-kappa antibody or a mixture of IgM- and IgD-isotype-specific antibodies, indicating that cross-linking of mIgD does not make B cell clones refractory to tolerogenic signal transduction through mIgM. These studies provide strong clonal support for the concept that coexpressed mIgM and mIgD molecules play distinct roles in human B cell immunoregulation.

Antigen-specific, but not natural killer, activity of T cell receptor-gamma delta cytotoxic T lymphocyte clones involves secretion of N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester serine esterase and influx of Ca2+ ions

Analysis of Ag specificity of TRC-gamma delta+ T cells in humans has been hampered by the fact that cloned lines of these cells expanded in IL-2 generally display high NK-like cytotoxic activity. A TCR-gamma delta+ CTL clone, isolated in IL-4, strongly lysed a specific stimulator cell, the EBV-transformed cell line JY, but failed to lyse K562 and other target cells sensitive for NK cell activity. Subsequent culture of this clone (CD124) in IL-2 induced high cytotoxic activity against the NK sensitive target cells. K562 cells were unable to induce the secretion of N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester [(BLT)-serine esterase] or influx of Ca2+ ions in clone CD124 cultured in either IL-4 or IL-2. In contrast, JY cells induced high BLT-serine esterase secretion and an increase of cytosolic Ca2+ levels. By using a combination of a 51Cr-release assay and a BLT-serine esterase secretion assay, the reactivity of clone CD124 against a limited number of target cells was analyzed. CD124 which expresses HLA-A2 and -B7, recognized an Ag shared by JY (HLA-A2; B7; C blank; DR4,6) and one haplotype expressed by the cell line SPS (HLA-A1; B14; Cw6; DR4). The only specificity shared by SPS and JY was HLA-DR4. However, clone CD124 failed to lyse 5 other HLA-DR4+ target cells. The cytotoxic activity of clone CD124 was inhibited by the class I MHC specific mAb W6/32 and the anti-beta 2m mAb A88, but not, or only marginally, by the anti HLA-DQ mAb SPV-L3 or the anti-HLA-DR mAb 135. These data strongly suggest that clone CD124 recognizes a class I MHC Ag different from HLA-A, -B, or -C.

Functional sites on the A alpha-chain. Polymorphic residues involved in antigen presentation to insulin-specific, Ab alpha:Ak beta-restricted T cells

The interaction between the clonally selected TCR, the processed Ag peptide and the Ia molecule is not fully understood in molecular terms. Our study intended to delineate the residues of Ab alpha molecules that function as contact sites for Ag and for the TCR of a panel of T cells specific for the A chain of insulin in combination with mixed haplotype Ab alpha:Ak beta molecules. Multiple L cell transfectants expressing alpha,beta-heterodimers composed of wild-type A beta- and chimeric or mutant A alpha-chains served as antigen presenting cells. The recombinant A alpha-chains had been generated by an exchange of allelically hypervariable regions (ahv) or amino acids. The results point out a broad spectrum of b sequence requirements for the bovine insulin-specific activation of the various T cell populations. Activation of some T cells seemed quite permissive, requiring b-haplotype amino acids in any one of the three ahv, while others had strict requirements, demanding b-haplotype sequence in all three ahv. Our data stress the role of ahvII and especially ahvIII in T cell activation. Interestingly, single amino-acid substitutions in ahvII or ahvIII of Ak alpha were sufficient to bring up full stimulation potential for two T cell hybridomas. We also found that some ahv permutations influenced the Ag preference (beef insulin versus pig insulin) of some T cells. These data suggest a critical role for the three-dimensional structure of the complex formed by Ia and the processed Ag peptide. The stability of the trimolecular complex essential for T cell activation is envisioned as being the sum of the interactions between Ag/I-A, TCR/Ag, and TCR/I-A, each variable in strength and compensated for by the others.

Analysis of the functional capabilities of CD3+CD4-CD8- and CD3+CD4+CD8+ human T cell clones

The functional capabilities of human peripheral blood CD3+CD4-CD8- and CD3+CD4+CD8+ T cell clones were examined. The clones were generated by culturing purified populations of CD3+CD4-CD8- and CD3+CD4+CD8+ T cells at limiting dilution (0.3 cell/well) in the presence of PHA, rIL-2, and irradiated PBMC as feeders. Twelve CD3+CD4-CD8- and 5 CD3+CD4+CD8+ clones were generated. Clonality was documented by analyzing TCR gamma- and beta-chain rearrangement patterns. All CD3+CD4-CD8- clones were stained by the TCR-delta 1 mAb that identifies a framework epitope of the TCR delta-chain, but not by mAb WT31 that identifies the TCR-alpha beta on mature T cells. In contrast, the CD3+CD4+CD8+ clones were all stained by WT31 and not by TCR-delta 1. All 17 clones were screened for various functional activities. Each secreted IL-2, IFN-gamma, and lymphotoxin/TNF-like factors when stimulated with immobilized mAb to CD3 (64.1), albeit in varying quantities. These clones secreted far less IL-2 and IFN-gamma than CD3+CD4+CD8- or CD3+CD4-CD8+ alpha beta expressing clones, but comparable amounts of lymphotoxin/TNF. All clones also functioned as MHC-unrestricted cytotoxic cells. This activity was comparable to that mediated by the CD3+CD4+CD8- or CD3+CD4-CD8+ alpha beta clones. Nine of 12 CD3+CD4-CD8- and 4 of 5 CD3+CD4+CD8+ clones were able to support B cell differentiation when activated by immobilized anti-CD3, but usually not as effectively as the CD3+CD4+CD8- or CD3+CD4-CD8+ alpha beta clones. The differences in the functional capabilities of the various clones could not be accounted for by alterations in the signaling capacity of the CD3 molecular complex as mAb to CD3 induced comparable increases in intracellular free calcium in each clone examined. When clones were stimulated with PWM, each suppressed B cell differentiation supported by mitomycin C-treated fresh CD4+ T lymphocytes. Suppression was dependent on the number of clone cells added to culture, but could be observed with as few as 12,500 cells per microtiter well. Phenotypic analysis of the clones revealed that all expressed CD29, CD11b, and the NKH1 surface Ag. These results demonstrate that the CD3+CD4-CD8- and CD3+CD4+CD8+ T cell clones exhibit many of the functional characteristics of mature T cells, although they produce IL-2 and IFN-gamma and provide help for B cell differentiation less effectively than CD3+CD4+CD8- and CD3+CD4-CD8+ alpha beta T cell clones.

Cloned natural suppressor cell lines express the CD3+CD4-CD8- surface phenotype and the alpha, beta heterodimer of the T cell antigen receptor

Several cloned lines of natural suppressor (NS) cells were studied for their expression of the TCR complex. Almost all bore the CD3+CD4-CD8- surface phenotype with the alpha, beta TCR as judged by immunofluorescent staining. Immunoprecipitation experiments showed a spot on two-dimensional gels which is characteristic of the TCR heterodimer, but neither gamma- nor delta-chains could be precipitated with the appropriate antibodies. NS cells were stimulated to proliferate in vitro with anti-CD3 antibodies and PMA in the presence of irradiated spleen cells. However, anti-CD3 antibodies did not inhibit the suppressive activity of the NS cells. The role of the TCR complex in the suppressive function of these cells remains to be elucidated.

Occurrence of mature B (IgM+, B220+) and T (CD3+) lymphocytes in scid mice

Scid mice with and without detectable serum Ig (scid Ig+ and scid Ig- mice, respectively) were examined for the presence of mature "leaky" lymphocytes by flow microfluorimetry with the use of antibodies to B (IgM, B220) and T (CD3, CD4, CD8) lymphocyte surface Ag. The data showed that leaky scid mice are more frequent than is evident from serum Ig analysis and that the incidence of detectable B and T cells increases with age. IgM+ B220+ cells were not detectable in young adult mice (3 mo old), but in old mice (greater than or equal to 1 yr old) they were routinely present in the peritoneal cavity though not in the spleen. Striking differences in the representation of T cell subsets were seen in the thymus of these two age groups. Most young adult mice contained CD3- populations of CD4/CD8 double positive cells, and in some cases, CD4 or CD8 single positive cells as well. By contrast, identifiable T lineage cells in old mice were all CD3+ and predominantly single positive for CD4 or CD8. Detectable peripheral T cell populations numbered less than 10(5) cells, and the representation of T subset markers (CD4, CD8) varied widely among individual mice; further, Southern blot analysis of TCR gene rearrangements in the DNA of polyclonally stimulated lymphoid cultures from these mice showed very restricted heterogeneity relative to that of cultures from normal mice. We conclude that most leaky mice contain very few T cell clones.

Functional alterations of herpes simplex virus-specific CD4+ multifunctional T cell clones following infection with human T lymphotropic virus type I

In an attempt to understand the mechanisms of immunodeficiency induced by human T lymphotropic virus type I (HTLV-I), HSV-specific CD4+ human multifunctional T cell clones were infected with HTLV-I in vitro. Early after HTLV-I infection, when their growth was still IL-2-dependent, clones were found to have almost completely lost their cytotoxic activity. At that time, their HSV-Ag-induced proliferative response and helper function for anti-HSV antibody production by B cells were only partially impaired. After this initial phase, the HTLV-I-infected clone became IL-2-independent, and the helper function was also completely lost. IL-2-dependent HTLV-I-infected clones showed degrees of proliferative response and elevation of intracellular free Ca2+ concentration induced by anti-CD3 mAb equivalent to those of HTLV-I-uninfected clones. On the other hand, during the IL-2-independent stage, expression of CD3-TCR complex on the cell surface was markedly decreased, and no significant elevation of intracellular free Ca2+ concentration was detected in response to anti-CD3 mAb. These data indicated that the loss of cytotoxic activity of HSV-specific T cell clones observed early after HTLV-I infection was not the result of impaired antigen recognition via the CD3-TCR complex, but might be due to dysfunction in the effector phase. On the other hand, the dysfunction of helper activity found late after HTLV-I infection might have mainly occurred in the recognition phase due to the decreased expression of CD3-TCR complex. The present data appear to suggest certain aspects of the pathogenesis of the immunodeficiency occurring in HTLV-I infection.

Clonogenic potential of murine CD4+8+ thymocytes. Direct demonstration using a V beta 6-specific proliferative stimulus in Mlsa mice

Although considerable indirect evidence supports the hypothesis that CD4+8+ thymocytes are developmental intermediates in the generation of mature (CD4+8- or CD4-8+) T cells, the ability of these cells to proliferate in vitro has been highly controversial. We demonstrate here that a fraction of purified murine CD4+8+ thymocytes can be induced to proliferate in response to immobilized anti-TCR mAb. To exclude possible proliferation by trace mature T cell contaminants, we have exploited our recent finding that in Mlsa mice mature V beta 6-bearing thymic T cells are virtually absent (less than or equal to 0.5%) due to clonal deletion, whereas V beta 6 +CD4+8+ thymocytes are present in much higher numbers (approximately 3%). Proliferation of sorted CD4+8+ thymocytes from Mlsa mice was therefore induced at limiting dilution with immobilized anti-V beta 6 mAb to select against any contaminating mature T cells. Under optimal culture conditions, the frequency of CD4+8+ thymocytes proliferating specifically to anti-V beta 6 mAb (1/1000) was higher than those obtained for purified CD4-8+ (1/2000) or CD4+8- (1/5000) subsets, thus demonstrating directly that a proportion (in this case 3%) of CD4+8+ thymocytes are potentially clonable. During culture, V beta 6 +CD4+8+ thymocytes gave rise to a mixture of phenotypically "immature" (CD4-8-) and "mature" (CD4-8+) T cells. This system should be valuable for further analysis of the elusive CD4+8+ thymocyte subset.

A new murine CD4+ T cell subset with an unrestricted cytokine profile

CD4+ T cell clones were derived from mice immunized to keyhole limpet hemocyanin to characterize the cytokine profiles of newly isolated clones. Surprisingly, several of the clones had an unrestricted profile, producing IL-2, IL-3, IL-4, IFN-gamma, and TNF after either Con A or Ag stimulation. The coproduction of IL-2 and IL-4 was confirmed at the mRNA level. Subclones were derived which contained RNA transcripts for, as well as secreted, both IL-2 and IL-4 thus confirming the clonality of the original T cell clones. CD4+ T cell clones that expressed an unrestricted cytokine profile upon Con A stimulation were also isolated from mice immunized to other Ag (hen egg lysozyme, OVA, or type II collagen). These data indicate that CD4+ T cell clones newly isolated from immunized mice do not necessarily segregate into the Th1 and Th2 subsets. We propose this new murine CD4+ cell subset with an unrestricted pattern of cytokine production be called Th0.

Arsonate-specific murine T cell clones. V. Antigen presentation by L cells transfected with normal and mutant class II genes

Class II-restricted murine T cell clones specific for the immunogenic determinant L-tyrosine-p-azobenzenearsonate failed to proliferate to Ag presented by L cell lines transfected with and expressing the appropriate class II genes, but are activated to kill the APC in an Ag-dependent, MHC-restricted manner. Inhibition of APC proliferation was used as an assay to determine the relative contributions of polymorphic sites on the class II alpha- and beta-chains to MHC-restricted activation of I-A beta k-restricted cloned T cells. Transfectants expressing A beta k in conjunction with the alpha chain of k, u, or d were equally effective APCs, whereas transfectants expressing A beta u were completely ineffective, implicating the beta-chain as more critical for the presentation of L-tyrosine-p-azobenzenearsonate. Site-directed mutagenesis of polymorphic positions in the beta chain revealed a remarkable stringency for the k haplotype, in contrast to the relaxed alpha-chain requirement. These results, in conjunction with others, indicate that the relative contribution of polymorphic sites on class II alpha- and beta-chains to T cell Ag recognition can differ markedly, and, furthermore, may vary as a function of the Ag.

Antigen specific and MHC nonrestricted cytotoxicity of T cell receptor alpha beta+ and gamma delta+ human T cell clones isolated in IL-4

IL-4 has been shown to act as a growth factor for human T cells. In addition, IL-4 can enhance CTL activity in MLC, but blocks IL-2 induced lymphokine activated killer cell activity in PBL. In our study, the cloning efficiencies, Ag-specific CTL activity and non-MHC-restricted cytotoxicity of CTL clones generated in IL-2 were compared to those generated in IL-4. In a first experiment, T cells were stimulated with the EBV-transformed B cell line JY and cloned 7 days later with feeder cells and either IL-2 or IL-4. In a second experiment, stimulation of the T cells was carried out in the presence of IL-2 plus anti-IL-4 antibodies or IL-4 plus anti-IL-2 antibodies in order to block the effects of IL-4 and IL-2, respectively, produced by the feeder cells. Although the cloning efficiencies in the second experiment were lower than those obtained in the first experiment, the cloning efficiencies obtained with IL-2 or IL-4 were similar in both experiments. The overall proportion of TCR alpha beta+ T cell clones cytotoxic for the stimulator cell JY established in IL-2 or IL-4 were comparable. A striking difference between the clones obtained in IL-2 or IL-4 was that a large proportion of the clones obtained in IL-4 expressed CD4 and CD8 simultaneously, whereas none of the clones isolated in IL-2 were double positive. Also gamma delta+ T cell clones could be established with IL-4 as a growth factor. TCR gamma delta+ T cell clones isolated in either IL-2 or IL-4 were CD4-CD8- or CD4-CD8+, but the proportion of CD4-CD8+ clones isolated in IL-4 was higher. Interestingly, one TCR gamma delta+ clone isolated in IL-2 was CD4+CD8-. Most of the TCR alpha beta+ and TCR gamma delta+ CTL-clones isolated in IL-2 lysed the NK cell sensitive target cell K562. In contrast, only a small proportion of the TCR alpha beta+ or TCR gamma delta+ CTL clones isolated in IL-4, lysed K562. One TCR gamma delta+ T cell clone (CD-124) isolated in IL-4 and subsequently incubated in IL-2 acquired lytic activity against K562.(ABSTRACT TRUNCATED AT 400 WORDS)

Hydrolysis of inositol phospholipids induced by stimulation of the T cell antigen receptor complex in antigen-specific, murine helper T cell clones. Requirement for exogenous calcium

Two murine, keyhole limpet hemocyanin-specific, Th cell clones were studied for their ability to respond to antibody-mediated stimulation of the TCR complex or to Ag-pulsed accessory cells by hydrolyzing inositol phospholipids. Both clones were positive for the determinant expressed on the epsilon chain of CD3 that is recognized by the mAb, 145-2C11 (2C11 mAb); one clone also expressed the V beta 8 epitope of the alpha/beta chains of the TCR recognized by the F23.1 mAb. Treatment of these cells with 2C11 or F23.1 mAb adsorbed onto polystyrene beads induced a time-dependent accumulation of inositol phosphates (IP). Keyhole limpet hemocyanin-pulsed accessory cells which expressed the appropriate MHC phenotype also induced IP accumulation, whereas no response was induced by medium-treated or MHC congenic accessory cells. The hydrolysis of inositol phospholipids induced by TCR perturbation depended upon the presence of exogenous Ca2+; Mg2+ did not substitute for Ca2+. Treatment of cells with ionomycin at concentrations up to 30 microM was unable to induce hydrolysis of inositol phospholipids, indicating that entrance of Ca2+ was itself insufficient to generate IP. Stimulated IP generation was rapidly blocked upon addition of EGTA to the incubation medium. Reducing the level of exogenous Ca2+ decreased the production of inositol mono-, bis-, and trisphosphate isomers similarly, suggesting that extracellular Ca2+ was required for the initiation of the hydrolysis rather than affecting phospholipase C affinity for its substrates. We concluded that activation of inositol phospholipid hydrolysis by perturbation of the TCR complex in the Th cell clones under investigation displays a Ca2+-dependent component which is likely to be proximal to IP generation.

Antiproliferative effect of IFN-gamma in immune regulation. III. Differential selection of TH1 and TH2 murine helper T lymphocyte clones using recombinant IL-2 and recombinant IFN-gamma

Supernatants collected after primary or secondary stimulation of spleen cells contain different arrays of lymphokines. Primary supernatants from spleen cells stimulated with Con A or allogeneic spleen cells (MLC-SF) contain IL-2 but little IL-4 or IGN-gamma; in contrast, secondary MLC-SF contains IL-2 as well as substantial IL-4 and IFN-gamma. Our laboratory previously had always used secondary MLC-SF for cloning T cells, and had routinely obtained TH1 helper T lymphocyte clones. In the present study, when primary Con A-SF was used as source of growth factors, TH2 and not TH1 clones were preferentially derived. Considering the possibility that IFN-gamma may be one important factor in determining whether TH1 or TH2 clones are preferentially obtained, clone derivation was then performed either in the presence of rIL-2 or rIL-2 plus rIFN-gamma. The majority of clones derived using rIL-2 alone were TH2 cells, whereas the majority of clones derived using rIL-2 plus rIFN-gamma were TH1 cells. Using either procedure, some clones were obtained that produced IL-2, IL-4, and IFN-gamma. These data are consistent with our previous observations that IFN-gamma inhibits the proliferation of TH2 but not TH1 clones, and suggest that the presence of IFN-gamma during an immune response would result in the preferential expansion of helper T lymphocytes of the TH1 phenotype. Our procedure for the differential selection of TH1 and TH2 clones reactive with the same Ag should be useful for designing in vitro systems for studying the function of these cell subsets in specific immune responses.

Transformation of growth factor-dependent myeloid stem cells with retroviral vectors carrying c-myc

Myeloid progenitor cells and macrophages derived from bone marrow and spleen were efficiently transformed in vitro by infection with Moloney-based retroviral vectors carrying a human c-myc gene. Infected cells were plated in agar in the presence of combinations of the murine lymphokines CSF-1, IL-3, GM-CSF and IL-1. Between 20% and 100% of the colony-forming cells in the initial bone marrow or spleen population could be infected and gave rise to drug-resistant colonies. A large fraction of the infected cells showed continued proliferation after transfer to liquid media and we have derived over 200 growth factor-dependent cell lines. These include adherent and non-adherent CSF-1 or GM-CSF dependent macrophages and macrophage precursors and cell lines which require complex combinations of growth factors for optimal growth. Each of the cell lines displays a unique pattern of expression of surface markers specific for the myeloid lineage including the Mac-1, Mac-2, Mac-3, Ser-4 and F4/80 antigens. Surface markers not specifically associated with the myeloid lineage such as the MHC class II antigens and the Fc-receptor; and surface markers normally associated with the B-cell and T-cell lineages such as B220, L3T4 and Thy1.2 are also found on these cell lines.

Clonal analysis of childhood acute lymphoblastic leukemia with "cytogenetically independent" cell populations

Acute lymphoblastic leukemia (ALL) is generally regarded as a clonal disease in which a single abnormal progenitor cell gives rise to neoplastic progeny. Five of 463 cases of childhood ALL with adequately banded leukemic cells were found to have two cytogenetically independent cell populations. In addition, two of the four cases tested had more than two rearranged immunoglobulin genes and (or) T cell receptor genes. To investigate the clonality of these unusual leukemias, we examined the neoplastic cells for X-linked markers extrinsic to the disease. Leukemic cells from each of the three patients heterozygous for an X-linked, restriction fragment length polymorphism showed a single active parental allele, suggesting that both apparently independent cell populations developed from a common progenitor. These cases provide evidence that leukemogenesis involves a multistep process of mutation and suggest that karyotypic abnormalities may be a late event of malignant transformation.

An alternative pathway of induction of lymphokine production by T lymphocyte clones

We have previously described a variant murine CTL clone that in contrast to all other clones tested, exhibited a novel capacity to produce IFN-gamma in response to IL-2. This alternative pathway of IFN-gamma induction differed from the conventional TCR complex-mediated pathway in that it was independent of elevated intracellular Ca2+ and insensitive to cyclosporine A. We report here the presence of an analogous pathway in the majority of T lymphocyte clones tested, when these clones are stimulated with IL-2 in the presence of syngeneic or third-party splenocytes. The accessory function of splenocytes in this alternative pathway is mediated by the MAC-1+ subpopulation and apparently involves cell-cell contact. However, the structure with which the MAC-1 antibody reacts probably is not involved directly. No involvement of Ag or the TCR for Ag could be demonstrated in this alternative pathway of lymphokine induction. The array of lymphokines induced by this alternative pathway is only a subset of those induced by antigenic stimulation. Finally, as with the previously described variant clone, IL-2-mediated induction of IFN-gamma production by the normal T lymphocyte clones is independent of normal extracellular Ca2+ levels and insensitive to cyclosporine A. Thus, this alternative pathway of lymphokine induction apparently constitutes a distinct signaling pathway in cloned T lymphocytes.

TCR gamma delta bearing lymphocyte clones with lymphokine-activated killer activity against autologous leukemic cells

Activated T lymphocytes with the T-cell receptor (TCR) gamma delta (CD3+ and TCR delta 1+) exhibit strong cytotoxic activity against the standard natural killer (NK) and lymphokine-activated killer (LAK) sensitive target cells. In order to test the cytotoxic activity of gamma delta T lymphocytes against autologous leukemic cells, 84 clones of gamma delta T lymphocytes were obtained from the peripheral blood of three acute lymphoblastic leukemia (ALL) patients. Forty-four of these T-cell clones were active against an LAK-sensitive cell line and the other 40 were active against K562, an NK target cell line. In each of the three patients, cytotoxic clones against autologous leukemic cells were obtained. Among the 84 clones, ten were able to kill autologous tumor cells, including eight that lyse the LAK-sensitive target and two with NK activity. The clones were highly cytotoxic, stable, and easily expanded in large quantity.