Endothelial cells require functional FLVCR1a during developmental and adult angiogenesis.

The Feline Leukemia Virus Subgroup C Receptor 1a (FLVCR1a) is a transmembrane heme exporter essential for embryonic vascular development. However, the exact role of FLVCR1a during blood vessel development remains largely undefined. Here, we show that FLVCR1a is highly expressed in angiogenic endothelial cells (ECs) compared to quiescent ECs. Consistently, ECs lacking FLVCR1a give rise to structurally and functionally abnormal vascular networks in multiple models of developmental and pathologic angiogenesis. Firstly, zebrafish embryos without FLVCR1a displayed defective intersegmental vessels formation. Furthermore, endothelial-specific Flvcr1a targeting in mice led to a reduced radial expansion of the retinal vasculature associated to decreased EC proliferation. Moreover, Flvcr1a null retinas showed defective vascular organization and loose attachment of pericytes. Finally, adult neo-angiogenesis is severely affected in murine models of tumor angiogenesis. Tumor blood vessels lacking Flvcr1a were disorganized and dysfunctional. Collectively, our results demonstrate the critical role of FLVCR1a as a regulator of developmental and pathological angiogenesis identifying FLVCR1a as a potential therapeutic target in human diseases characterized by aberrant neovascularization.

Bone remodelling and integration of two different types of short stem: a dual-energy X-ray - absorptiometry study.

PURPOSE: Different kinds of bone preserving hip stems have been created to assure a more physiological distribution of the strengths on the femur. The aim of this research is to evaluate the density reaction of the periprosthetic bone while changing the conformation of the prosthetic implant on dual-energy X-ray - absorptiometry (DXA). METHODS: This is a prospective, single-centre study assessing bone remodelling changes after implantation of two short hip stems, dividing the patients in two groups according to the implant used: 20 in group A, Metha (B-Braun), and 16 in group B, SMF (Smith and Nephew). All participants had a pre-operative and a post-operative (24 months) DXA evaluating the changes in bone mass density (BMD) occurred in the five Gruen's zones. RESULTS: Compared to the pre-operative value, differences in BMD percentage were statistically significant only in ROI 4 (p < 0.05), with an increase in both groups (9 and 18%, respectively). The average increase in BMD was of 7.3% and 7.2% in the 2 groups. CONCLUSION: According to our study, both stems have proved able to provide good load distribution across the metaphyseal region favouring proper system integration. Nonetheless, is certainly needed to perform other studies with longer follow-up and bigger populations to give strength to these conclusions.

Chiral Spin Texture in the Charge-Density-Wave Phase of the Correlated Metallic Pb/Si(111) Monolayer.

We investigate the 1/3 monolayer α-Pb/Si(111) surface by scanning tunneling spectroscopy (STS) and fully relativistic first-principles calculations. We study both the high-temperature sqrt[3]×sqrt[3] and low-temperature 3×3 reconstructions and show that, in both phases, the spin-orbit interaction leads to an energy splitting as large as 25% of the valence-band bandwidth. Relativistic effects, electronic correlations, and Pb-substrate interaction cooperate to stabilize a correlated low-temperature paramagnetic phase with well-developed lower and upper Hubbard bands coexisting with 3×3 periodicity. By comparing the Fourier transform of STS conductance maps at the Fermi level with calculated quasiparticle interference from nonmagnetic impurities, we demonstrate the occurrence of two large hexagonal Fermi sheets with in-plane spin polarizations and opposite helicities.

Analysis of small-scale soil CO2 fluxes in an orange orchard under irrigation and soil conservative practices.

The quantification of soil carbon dioxide (CO2) flux represents an indicator of the agro-ecosystems sustainability. However, the monitoring of these fluxes is quite challenging due to their high spatially-temporally variability and dependence on environmental variables and soil management practices.In this study, soil CO2 fluxes were measured using a low-cost accumulation chamber, that was realized ad hoc for the surveys, in an orange orchard managed under different soil management (SM, bare versus mulched soils) and water regime (WR, full irrigation versus regulated deficit irrigation) strategies. In particular, the soil CO2 flux measurements were acquired in discontinuous and continuous modes, together with ancillary agrometeorological and soil-related information, and then compared to the agrosystem scale CO2 fluxes measured by the eddy covariance (EC) technique.Overall significant differences were obtained for the soil CO2 discontinuous fluxes as function of the WR (0.16 ± 0.01 and 0.14 ± 0.01 mg m-2 s-1 under full irrigation and regulated deficit irrigation, respectively). For the continuous soil CO2 measurements, the response observed for the SM factor varied from year to year, indicating for the overall reference period 2022-23 higher soil CO2 flux under the mulched soils (0.24 ± 0.01 mg m-2 s-1) than under bare soil conditions (0.15 ± 0.00 mg m-2 s-1). Inter-annual variations were also observed as function of the day-of-year (DOY), the SM and their interactions, resulting in higher soil CO2 flux under the mulched soils (0.24 ± 0.02 mg m-2 s-1) than under bare soil (0.15 ± 0.01 mg m-2 s-1) in certain periods of the years, according to the environmental conditions. Results: suggest the importance of integrating soil CO2 flux measurements with ancillary variables that explain the variability of the agrosystem and the need to conduct the measurements using different operational modalities, also providing for night-time monitoring of CO2. In addition, the study underlines that the small-scale chamber measurements can be used to estimate soil CO2 fluxes at orchard scale if fluxes are properly scaled.

High twinning rate in Cândido Godói: a new role for p53 in human fertility.

BACKGROUND: Cândido Godói (CG) is a small town in South Brazil, which has the highest prevalence of twin births in Brazil. Recently, a number of studies have shown that p53 plays an important role in reproduction through blastocyst implantation and intra utero embryo survival. Thus, gene polymorphisms in the p53 pathway were investigated in this population. METHODS: Single nucleotide polymorphisms from five genes in the p53 pathway were investigated, as well as background characteristics of 42 mothers of twins (cases) and 101 mothers of singletons (controls), all residents from CG. RESULTS: Mothers of twins have higher number of pregnancies and higher frequencies of P72 allele at TP53 and T allele at MDM4 genes compared with controls. Logistic regression shows that both TP53 and number of pregnancies maintained their association with twinning (P =0.004 and P =0.002, respectively), with TP53 having a higher odds ratio than number of pregnancies (2.73 versus 1.70, respectively). No interactive effect between TP53 and MDM4 (P =0.966) is observed. As expected, mothers of twins have three times more cases of cancer in their first-degree relatives than control mothers (P =0.011). CONCLUSIONS: Our results suggest that the P72 allele of TP53 is a strong risk factor for twinning in CG, while the number of pregnancies and the T allele at MDM4 may represent weaker risk factors. These two alleles are associated with infertility, but the anti-apoptotic effect of low levels of p53 in general, and of the P72 allele in particular, may play a role after implantation, enhancing the chance for a double pregnancy to succeed to term.

Central nervous system tuberculosis in non-HIV-positive children: a single-center, 6 year experience.

PURPOSE: The aim of this paper is to describe the imaging features of central nervous system (CNS) tuberculosis on computed tomography (CT) and magnetic resonance imaging (MRI) studies in non-HIV-positive children. MATERIALS AND METHODS: A retrospective descriptive evaluation was conducted on imaging studies obtained from ten children admitted to our hospital over a 6-year period who fulfilled criteria for a diagnosis of CNS tuberculosis. Data were collected with regard to patients' clinical, laboratory and demographic characteristics, as well as results of radiological investigation. RESULTS: We studied ten children, of whom five were boys and five were girls and whose mean age was 4 (range 7 months to 16) years. Neuroradiological findings on the first imaging study were basal meningeal enhancement (100%), hydrocephalus (70%), infarcts (90%), tuberculomas (40%) and cranial nerve involvement (20%). Follow-up studies revealed basal meningeal enhancement, hydrocephalus, and infarcts in all patients, tuberculomas in 70% and cranial nerve involvement in 50%. Only one patient showed a pattern of miliary tuberculosis. CONCLUSIONS: CNS tuberculosis is still an important cause of childhood morbidity and mortality even in nonimmunosuppressed children. Because prompt diagnosis results in earlier treatment, it is crucial to be aware of tuberculous meningitis and its complications at imaging, especially because of the impact on patients' prognosis.

DTI parameters in neonates with hypoxic-ischemic encephalopathy after total body hypothermia.

BACKGROUND AND PURPOSE: MR imaging provides means for discriminating different patterns of Hypoxic-ischemic encephalopathy (HIE) and may distinguish most severe cases from less severe but is unable to predict long-term outcome. Diffusion tensor imaging (DTI) offers information for a more complete characterization of HIE. The purpose of this study is to compare the modifications of DTI parameters in newborns one week and six months following total-body cooling to healthy controls. METHODS: Forty-seven cooled newborns were studied with MRI, 20 underwent follow-up at 6 months. 12 healthy newborns and nine children at 6 months were enrolled as control groups (HC). Inferior Longitudinal Fasciculus (ILF), Corpus Callosum Fasciculus (CCF), Corticospinal Tract (CST), Optical Tract (OT), Optic Radiation (OR) were generated in all subjects. DTI parameters were evaluated in basal ganglia (BG), thalamus (TH) and tracks. Statistical analysis was performed with MANOVA. RESULTS: In newborns HIE versus HC, there were significantly lower fractional anisotropy (FA) on OR and CST and higher axial diffusivity (AD), apparent diffusion coefficient (ADC) and radial diffusivity (RD) values on CST, BG and TH in HIE-N. At 6 months there were no significant grouping effects. The analysis showed a significant increase of FA, decrease of ADC, AD, RD after 6 months for HIE and HC. CONCLUSIONS: We observed modifications of parameter values in HIE newborns vs HC; however normalization of values at 6 months suggests that changes of parameters cannot be considered early biomarkers for evaluation of therapeutic hypothermia in newborns with moderate HIE and normal conventional MRI.

Childhood refractory focal epilepsy following acute febrile encephalopathy.

BACKGROUND: We describe a group of previously normal children who developed severe focal epilepsy after an acute/sub-acute illness resembling encephalitis. METHODS: This is a retrospective study. An acute phase (encephalitis/encephalopathy period) and a chronic phase (chronic focal resistant epilepsy) were defined. RESULTS: Eight patients were enrolled. The median age at onset was 6.6 years (range 8 months-17.6 years). In the acute phase, fever was the first symptom in all cases and was associated with seizures and status epilepticus. All patients had focal seizures arising in both hemispheres. Seizure onset occurred in the frontal and temporal regions. EEGs showed slowing background activity associated with focal or diffuse slow waves with rare epileptiform abnormalities. Cerebrospinal fluid oligoclonal bands were observed in four out of six patients tested. MRI images showed bilateral peri-insular hyperintensity in four cases. Five patients received corticosteroids, and in four cases, they were given along with intravenous immunoglobulins. The median duration of the acute phase was 19 days (range 15-30 days). During the chronic phase, which followed the acute phase without interval, patients presented with drug-resistant focal seizures and neuropsychological deficits, which ranged from hyperactivity and attention deficits to short-term verbal memory deficit, pervasive developmental disorders, and language delay. CONCLUSION: Considering the clinical presentations, EEG findings, and the associated occurrence of non-specific immunological activations, a possible immune-mediated pathogenesis can be hypothesized, although firm conclusions cannot be drawn out.

Complete molecular remissions induced by patient-specific vaccination plus granulocyte-monocyte colony-stimulating factor against lymphoma.

Lymphomas express a tumor-specific antigen which can be targeted by cancer vaccination. We evaluated the ability of a new idiotype protein vaccine formulation to eradicate residual t(14;18)+ lymphoma cells in 20 patients in a homogeneous, chemotherapy-induced first clinical complete remission. All 11 patients with detectable translocations in their primary tumors had cells from the malignant clone detectable in their blood by PCR both at diagnosis and after chemotherapy, despite being in complete remission. However, 8 of 11 patients converted to lacking cells in their blood from the malignant clone detectable by PCR after vaccination and sustained their molecular remissions. Tumor-specific cytotoxic CD8+ and CD4+ T cells were uniformly found (19 of 20 patients), whereas antibodies were detected, but apparently were not required for molecular remission. Vaccination was thus associated with clearance of residual tumor cells from blood and long-term disease-free survival. The demonstration of molecular remissions, analysis of cytotoxic T lymphocytes against autologous tumor targets, and addition of granulocyte-monocyte colony-stimulating factor to the vaccine formulation provide principles relevant to the design of future clinical trials of other cancer vaccines administered in a minimal residual disease setting.

Gestational Diabetes Mellitus: Clinical Characteristics and Perinatal Outcomes in a Multiethnic Population of North Italy.

AIM: To evaluate clinical characteristics and perinatal outcomes in a heterogeneous population of Caucasians born in Italy and High Migration Pressure Countries (HMPC) women with GDM living in Piedmont, North Italy. METHODS: We retrospectively analyzed data from 586 women referring to our unit (2015-2020). Epidemiological (age and country of origin) and clinical-metabolic features (height, weight, family history of DM, parity, previous history of GDM, OGTT results, and GDM treatment) were collected. The database of certificates of care at delivery was consulted in relation to neonatal/maternal complications (rates of caesarean sections, APGAR score, fetal malformations, and neonatal anthropometry). RESULTS: 43.2% of women came from HMPC; they were younger (p < 0.0001) and required insulin treatment more frequently than Caucasian women born in Italy (χ 2 = 17.8, p=0.007). Higher fasting and 120-minute OGTT levels and gestational BMI increased the risk of insulin treatment (OGTT T0: OR = 1.04, CI 95% 1.016-1.060, p=0.005; OGTT T120: OR = 1.01, CI 95% 1.002-1.020, p=0.02; BMI: OR = 1.089, CI 95% 1.051-1.129, p < 0.0001). Moreover, two or more diagnostic OGTT glucose levels doubled the risk of insulin therapy (OR = 2.03, IC 95% 1.145-3.612, p=0.016). We did not find any association between ethnicities and neonatal/maternal complications. CONCLUSIONS: In our multiethnic GDM population, the need for intensive care and insulin treatment is high in HPMC women although the frequency of adverse peripartum and newborn outcomes does not vary among ethnic groups. The need for insulin therapy should be related to different genetic backgrounds, dietary habits, and Nutrition Transition phenomena. Thus, nutritional intervention and insulin treatment need to be tailored.

Neuroradiologic Phenotyping of Galactosemia: From the Neonatal Form to the Chronic Stage.

Galactosemia is a rare genetic condition caused by mutation of enzymes involved in galactose and glucose metabolism. The varying clinical spectrum reflects the genetic complexity of this entity manifesting as acute neonatal toxicity syndrome, requiring prompt diagnosis and treatment, to more insidious clinical scenarios as observed in the subacute and chronic presentations. The current literature predominantly focuses on the long-standing sequelae of this disease. The purpose of this multicenter clinical report comprising 17 patients with galactosemia is to highlight the MR imaging patterns encompassing the whole spectrum of galactosemia, emphasizing the 3 main clinical subtypes: 1) acute neonatal presentation, with predominant white matter edema; 2) subacute clinical onset with a new finding called the "double cap sign"; and 3) a chronic phase of the disease with heterogeneous imaging findings. The knowledge of these different patterns together with MR spectroscopy and the clinical presentation may help in prioritizing galactosemia over other neonatal metabolic diseases and prevent possible complications.

Gene complementation. Neither Ir-GLphi gene need be present in the proliferative T cell to generate an immune response to Poly(Glu55Lys36Phe9)n.

The cellular requirements for immune response (Ir) gene expression in a T cell proliferative response under dual Ir gene control were examined with radiation-induced bone marrow chimeras. The response to poly(Glu55Lys36Phe9)n (GLphi) requires two responder alleles that in the [B10.A X B10.A(18R)]F1 map in I-Ab and I-Ek/Cd. Chimeras in which a mixture of the nonresponder B10.A parental cells (which possess only I-Ek/Cd) and the nonresponder B10.A(18R) parental cells (which possess only I-Ab) were allowed to mature in a responder F1 environment did not respond to GLphi, which suggests that at least one cell participating in the response needed to possess both responder alleles to function. When T cells from such A + 18R leads to F1 chimeras were primed in the presence of responder antigen-presenting cells (APC), the chimeric T cells responded to GLphi, which suggests that both responder alleles must be expressed in the APC but not necessarily in the T cell. Interestingly, acutely irradiated F1 animals were found not to be an adequate source of responder APC for priming the proliferating T cell because of the rapid turnover of peripheral APC after irradiation. In adoptive transfer experiments, T cell-depleted bone marrow had to be used as a source of responder APC. When bone marrow cells from (B10.A X B10)F1 responder animals were allowed to mature in a low-responder B10 of B10.A parental environment, neither chimera, F1 leads to A or F1 leads to B, could respond to GLphi. This demonstrated that the presence of high-responder APC, which derive from the donor bone marrow, was not sufficient to generate a GLphi response. It appears that in addition it is essential for the T lymphocytes to mature in a high-responder environment. Finally, B10.A(4R) T cells, which possess neither Ir-GLphi responder allele, could be educated to mount a GLphi-proliferative response provided that they matured in a responder environment and were primed with APC expressing both responder alleles. Therefore, the gene products of the complementing Ir-GLphi responder alleles appear to function as a single restriction element at the level of the APC. T cells that do not possess responder alleles are not intrinsically defective, because they could be made phenotypic responders if they developed in an environment in which responder major histocompatibility complex (MHC) products were learned as self and if antigen was presented to them by APC expressing responder MHC products.

Preferential differentiation of T cell receptor specificities based on the MHC glycoproteins encountered during development. Evidence for positive selection.

T cells recognize foreign antigens together with those MHC glycoproteins they have encountered during their development in the thymus. How the repertoire of antigen-specific TCRs is selected has not yet been fully defined. We have investigated the T cell repertoire specificities of CD4-CD8+ cytotoxic T cells developing under conditions where one of the class I MHC-encoded molecules is blocked, while other class I-MHC glycoproteins are still expressed. We show that antigen-specific T cells restricted to the blocked class I fail to develop, while generation of other class I-specific T cell proceeds undisturbed. This highly selective perturbation of the T cell receptor repertoire demonstrates that development of CD4-CD8+ T cells with a certain TCR specificity requires expression of particular alleles of class I MHC. Thus, TCR-MHC interactions provide signals essential to the differentiation of precursor T cells.

B lymphocyte immune response gene phenotype is genetically determined.

We examined the effects of the developmental milieu on the capacity of B cells to undergo immune response gene-controlled, T cell-dependent polyclonal proliferation. Although I-Aq poly(Glu60 Ala30 Tyr10)n (GAT)-nonresponder T cells developing in a responder environment become phenotypic GAT-responders, I-Aq B cells remain unresponsive to GAT, even after maturation in a GAT-responder animal. Conversely, (B10.A x B10.Q)F1 ([GAT responder x GAT nonresponder]F1) T cells developing in a B10.Q GAT nonresponder host fail to respond to GAT, but F1 B cells from the same F1 leads to parent chimeras make excellent proliferative responses in the presence of GAT and responder T cells. Thus, by this assay, B cell immune response gene function is genetically determined and is not affected by the developmental milieu.

Murine syngeneic mixed lymphocyte response. I. Target antigens are self Ia molecules.

A system has been described that produces a murine syngeneic mixed lymphocyte response (MLR) comparable in magnitude to an allogeneic MLR. The responder cells in these cultures exhibit the classic immunologic characteristics of both memory and specificity. Studies using radiation-induced bone marrow chimeras of F(1) {arrow} parent type indicated that, similar to many other T cell-mediated immune responses, the response of the T lymphocytes in the syngeneic MLR was major histocompatibility complex-restricted and was determined by the environment in which the T cells matured. Using responder T cells from F(1) {arrow} parent chimeras and stimulator cells from H-2 recombinant strains, it was possible to map the genes involved in the stimulation to the K and/or I regions. In addition, blocking studies with monoclonal anti-Ia antibodies suggested that in the B10.A strain the critical molecules were products of both the I-A(k) and I-E(k) subregions. The issue of whether the syngeneic MLR is directed solely at self I-region antigens or whether the response represents proliferation to an unknown antigen in association with self I-region determinants was also addressed. Secondary syngeneic MLR were successfully performed in normal mouse serum and with stimulator cells prepared in the absence of bovine serum albumin to rule out the possibility that xenogeneic serum antigens were involved in the stimulation. The possibility that the syngeneic MLR might represent a secondary response to environmental antigens was eliminated by using germ- free mice as a source of stimulator cells and by demonstrating that spleen cells from unimmunized, fully allogeneic chimeras (B10.A {arrow} B10) could generate a normal syngeneic MLR even though such chimeras could not be primed to respond to any foreign antigens unless supplemented in vivo with a source of antigen-presenting cells syngeneic to the B10 host. The possibility that the syngeneic MLR was a primary response to a foreign antigen was considered unlikely because by using our culture conditions we could not obtain a primary antigen response or a secondary antigen response after in vitro priming to a variety of potent foreign antigens. Finally, the possibility that the syngeneic MLR represents a response to a variety of minor histocompatibility self antigens in association with self Ia molecules was eliminated by showing that the secondary responses to H-2 compatible, non-H-2 different strain (A/J vs. B10.A and C3H, or BALB/c vs. B10.D2 and DBA/2) were comparable to the secondary responses to syngeneic stimulators. Thus, we conclude that the target antigens in the syngeneic MLR are solely determinants on self Ia molecules, although the functionally equivalent possibility of a single, nonpolymorphic, minor self antigen seen in association with self Ia molecules cannot be excluded.

Differential effects of growth hormone and prolactin on murine T cell development and function.

DW/J dwarf mice have a defect in their anterior pituitary and are deficient in growth hormone (GH) and prolactin (PRL). These mice have been demonstrated previously to have a deficiency in CD4/CD8 double-positive thymocytes, which could be corrected by treatment of these mice with recombinant human GH. Since PRL has been implicated in T cell function and human GH can interact with the PRL receptor, DW/J dwarf mice were treated with either ovine GH (ovGH) (20 micrograms/d) or ovine PRL (ovPRL) (20 micrograms/d). The ovine hormones can only bind their own specific receptors in the mouse. After several weeks of treatment, it was found that these two hormones produced markedly contrasting effects on T cells. Phenotypic analysis of the lymphoid organs was performed by flow cytometry and the functional capability of the peripheral T cells was assessed by immunizing the mice and determining the extent of antigen-specific proliferation of T cells obtained from the draining lymph nodes or by determining splenic mitogen responses. The results indicated that ovGH administration to dwarf mice resulted in significant increases in thymic cellularity yet had little effect on peripheral T cell responses. In contrast, the administration of ovPRL resulted in a further decrease in thymic cellularity when compared with untreated dwarf mice. No thymic effects of either ovGH or ovPRL administration were detected on the normal +/? counterparts. However, ovPRL administration resulted in a significant increase in the number and function of antigen-specific peripheral T cells in both immunized dwarf and +/? mice. The adjuvant effects of PRL occurred even though the mice also received complete Freund's adjuvant. These results suggest that neuroendocrine hormones may act in concert in T cell development. GH appears to promote thymocyte proliferation, while PRL appears to decrease thymus size and yet augment the number and function of antigen-specific T cells in the periphery.

CD8 is required during positive selection of CD4-/CD8+ T cells.

Interactions between self-MHC molecules and T cells are necessary for the proper development of mature T cells, in part due to an absolute requirement for self-MHC-TCR interactions. Recently, we showed that CD4-mediated interactions also participate in shaping the T cell repertoire during thymic maturation. We now examine the possible role of the CD8 molecule during in vivo T cell development. Our results demonstrate that perinatal thymi treated with intact anti-CD8 mAb fail to generate CD8 single-positive T cells, while the generation of the other main phenotypes remains unchanged. Most importantly, the use of F(ab')2 anti-CD8 mAb fragments gave identical results, i.e., lack of generation of CD4-/CD8+ cells, with no effect on the generation of CD4+/CD8+. Furthermore, selective blocking of one CD8 allele with F(ab')2 mAbs in F1 mice expressing both CD8 alleles did not interfere with the development of CD4-/CD8+ cells, demonstrating that the absence of CD8+ T cells in homozygous mice is not due to depletion, but rather is caused by a lack of positive selection. This is most likely attributable to a deficient CD8-MHC class I interaction. Our findings strongly advocate that CD8 molecules are vital to the selection process that leads to the development of mature single-positive CD8 T cells.

Self-recognition specificity expressed by T cells from nude mice. Absence of detectable Ia-restricted T cells in nude mice that do exhibit self-K/D-restricted T cell responses.

The presence in athymic nude mice of precursor T cells with self-recognition specificity for either H-2 K/D or H-2 I region determinants was investigated. Chimeras were constructed of lethally irradiated parental mice receiving a mixture of F1 nude mouse (6-8 wk old) spleen and bone marrow cells. The donor inoculum was deliberately not subjected to any T cell depletion procedure, so that any potential major histocompatibility complex-committed precursor T cells were allowed to differentiate and expand in the normal parental recipients. 3 mo after reconstitution, the chimeras were immunized with several protein antigens in complete Freund's adjuvant in the footpads and their purified draining lymph node T cells tested 10 d later for ability to recognize antigen on antigen-presenting cells of either parental haplotype. Also, their spleen and lymph node cells were tested for ability to generate a cytotoxic T lymphocyte (CTL) response to trinitrophenyl (TNP)-modified stimulator cells of either parental haplotype. It was demonstrated that T cell proliferative responses of these F1(nude)----parent chimeras were restricted solely to recognizing parental host I region determinants as self and expressed the Ir gene phenotype of the host. In contrast, CTL responses could be generated (in the presence of interleukin 2) to TNP-modified stimulator cells of either parental haplotype. Thus these results indicate that nude mice which do have CTL with self-specificity for K/D region determinants lack proliferating T cells with self-specificity for I region determinants. These results provide evidence for the concepts that development of the I region-restricted T cell repertoire is strictly an intrathymically determined event and that young nude mice lack the unique thymic elements responsible for education of I region-restricted T cells.

Selection of antigen-specific, idiotype-positive B cells in transgenic mice expressing a rearranged M167-mu heavy chain gene.

Flow cytometric analysis of antigen-specific, idiotype-positive (id+), B cell development in transgenic mice expressing a rearranged M167-mu gene shows that large numbers of phosphocholine (PC)-specific, M167-id+ B cells develop in the spleen and bone marrow of these mice. Random rearrangement of endogenous V kappa genes, in the absence of a subsequent receptor-driven selection, should give rise to equal numbers of T15- and M167-id+ B cells. The observed 100-500-fold amplification of M167-id+ B cells expressing an endogenous encoded V kappa 24]kappa 5 light chain in association with the M167 VH1-id transgene product appears to be an antigen driven, receptor-mediated process, since no amplification of non-PC-binding M167 VH1/V kappa 22, T15-id+ B cells occurs in these mu-only transgenic mice. The selection and amplification of antigen-specific, M167-id+ B cells requires surface expression of the mu transgene product; thus, no enhancement of M167-id+ B cells occurs in the M167 mu delta mem-transgenic mice, which cannot insert the mu transgene product into the B cell membrane. Surprisingly, no selection of PC-specific B cells occurs in M167-kappa-transgenic mice although large numbers of B cells expressing a crossreactive M167-id are present in the spleen and bone marrow of these mice. The failure to develop detectable numbers of M167-id+, PC-specific B cells in M167-kappa-transgenic mice may be due to a very low frequency of M167-VH-region formation during endogenous rearrangement of VH1 to D-JH segments. The somatic generation of the M167 version of a rearranged VH1 gene may occur in less than one of every 10(5) bone marrow B cells, and a 500-fold amplification of this M167-Id+ B cell would not be detectable by flow cytometry even though the anti-PC antibody produced by these B cells is detectable in the serum of M167-kappa-transgenic mice after immunization with PC.

Essential role of the interleukin 2-interleukin 2 receptor pathway in thymocyte maturation in vivo.

The role of the IL-2-IL-2-R pathway in thymocyte differentiation in vivo is unknown. We have examined fetal thymocyte development in vivo, under conditions where all IL-2-R were saturated from day 13 of gestation with anti-IL-2-R mAbs that were previously shown to render mature T cells unable to respond to IL-2. This produced a dramatic change in the composition of developing T cells: thymocytes from day 1 neonatal mice born to anti-IL-2-R-treated mothers did not contain CD4+ or CD8+ single-positive cell populations. In addition, no generation of surface TCR beta chain-expressing T cells or antigen-reactive functional T cells occurred in treated mice. These data suggest that IL-2-IL-2-R interactions provide signals crucial to in vivo intrathymic development of mature T cells.