Parameter perturbations in a post-treatment chronic myeloid leukemia model capture the essence of pre-diagnosis A-bomb survivor mysteries.

A model of post-diagnosis chronic myeloid leukemia (CML) dynamics across treatment cessations is applied here to pre-diagnosis scenarios of A-bomb survivors. The main result is that perturbing two parameters of a two-state simplification of this model captures the essence of two A-bomb survivor mysteries: (1) in those exposed to > 1 Sv in Hiroshima, four of six female onsets arose as a cluster in 1969-1974, well after 5-10-year latencies expected and observed in two of six female- and nine of ten male cases (about one background case was expected in this high-dose cohort); and (2) no Nagasaki adult cases exposed to > 0.2 Sv were observed though about nine were expected (~ 1.5 background + ~ 7.5 radiation-induced). Overall, it is concluded that: (1) whole-body radiation co-creates malignant and benign BCR-ABL clones; (2) benign clones are more likely to act as anti-CML vaccines in females than in males; (3) the Hong Kong flu of 1968 (and H3N2 seasonal flu thereafter) exhausted anti-CML immunity, thereby releasing radiation-induced clones latent in high-dose Hiroshima females; and (4) benign cells of 1-2 are CD4+ as human T-cell leukemia-lymphoma virus-1 endemic to Nagasaki but not Hiroshima expands numbers of such cells. The next goal is to see if these conclusions can be substantiated using banked A-bomb survivor blood samples.

RADIATION-INDUCED BYSTANDER EFFECT - MODELING, MANIFESTATION, MECHANISMS, PERSISTENCE, CANCER RISKS (literature review). / RADIATsIY̆NO-INDUKOVANYY̆ EFEKT SVIDKA ­ MODELIuVANNIa, PROIaVY, MEKhANIZMY ROZVYTKU, PERSYSTENTsIIa, ONKOLOGIChNI RYZYKY (ogliad literatury).

The review summarizes and analyzes the data of world scientific literature and the results of the own research con- cerning one of the main non-targeted effects of ionizing radiation - the radiation induced bystander effect (RIBE) - the ability of irradiated target cells to induce secondary biological changes in non-irradiated receptor cells. The his- tory of studies of this phenomenon is presented - it described under various names since 1905, began to study from the end of the twentieth century when named as RIBE and caused particular interest in the scientific community during recent decades. It is shown that the development of biological science and the improvement of research methods allowed to get new in-depth data on the development of RIBE not only at the level of the whole organism, but even at the genome level. The review highlights the key points of numerous RIBE investigations including mod- eling; methodological approaches to studying; classification; features of interaction between irradiated and intact cells; the role of the immune system, oxidative stress, cytogenetic disorders, changes in gene expression in the mechanism of development of RIBE; rescue effect, abscopal effect, persistence, modification, medical effects. It is emphasized that despite the considerable amount of research concerning the bystander response as the universal phenomenon and RIBE as one of its manifestations, there are still enough «white spots¼ in determining the mech- anisms of the RIBE formation and assessing the possible consequences of its development for human health.

Lymphoid and Myeloid Recovery in Rhesus Macaques Following Total Body X-Irradiation.

Recovery from severe immunosuppression requires hematopoietic stem cell reconstitution and effective thymopoiesis to restore a functional immune cell repertoire. Herein, a model of immune cell reconstitution consequent to potentially lethal doses of irradiation is described, which may be valuable in evaluating potential medical countermeasures. Male rhesus macaques were total body irradiated by exposure to 6.00 Gy 250 kVp x-radiation (midline tissue dose, 0.13 Gy min), resulting in an approximate LD10/60 (n = 5/59). Animals received medical management, and hematopoietic and immune cell recovery was assessed (n ≤ 14) through 370 d post exposure. A subset of animals (n ≤ 8) was examined through 700 d. Myeloid recovery was assessed by neutrophil and platelet-related parameters. Lymphoid recovery was assessed by the absolute lymphocyte count and FACS-based phenotyping of B- and T-cell subsets. Recent thymic emigrants were identified by T cell receptor excision circle quantification. Severe neutropenia, lymphopenia, and thrombocytopenia resolved within 30 d. Total CD3+ cells µL required 60 d to reach values 60% of normal, followed by subsequent slow recovery to approximately normal by 180 d post irradiation. Recovery of CD3+4+ and CD3+8+ cell memory and naïve subsets were markedly different. Memory populations were ≥ 100% of normal by day 60, whereas naïve populations were only 57% normal at 180 d and never fully recovered to baseline post irradiation. Total (CD20+) B cells µL were within normal levels by 77 d post exposure. This animal model elucidates the variable T- and B-cell subset recovery kinetics after a potentially lethal dose of total-body irradiation that are dependent on marrow-derived stem and progenitor cell recovery, peripheral homeostatic expansion, and thymopoiesis.

Aetiology of childhood acute leukaemias: current status of knowledge.

Acute leukaemia is a consequence of malignant transformation of a haematopoetic progenitor cell. Molecular studies have revealed a prenatal origin of many childhood leukaemias. According to current models, a preleukaemic stem cell clone is generated by a first mutation in utero which, in a minority of children, progresses to leukaemia after receiving further postnatal genetic hits. The nature of pre- and postnatal events involved in leukaemogenesis in children is not well understood. Although genetic predisposition and specific environmental exposures may account for individual cases, the bulk of childhood leukaemia cannot be explained by any of these factors. The higher incidence of the most common leukaemia subtype in affluent societies, as well as the age peak between 2-5 y, suggest a contributory role of socioeconomic factors. An abnormal immune response during delayed exposure to common infections provides a plausible mechanism for malignant progression of preleukaemic clones in a subgroup of children. As highlighted in this review, a common cause for all types and subtypes of childhood leukaemia is highly unlikely. Deeper insights into the pathogenesis of childhood leukaemia will rely on large-scale and combined epidemiological and biomolecular studies.

Identification of a CD4 T-cell epitope in tumor rejection antigen RLakt on BALB/c radiation-leukemia RL male 1.

We have previously shown that the RLakt antigen was predominantly recognized by CD8 cytotoxic T lymphocytes (CTL) in RL male 1-bearing or -rejected syngeneic BALB/c mice. CD8 CTL were directed to the octamer pRL1a peptide IPGLPLSL of which recognition was H-2L(d)-restricted. In this study, we identified a CD4 T-cell epitope peptide in the tumor rejection antigen RLakt on BALB/c radiation-leukemia RL male 1. Analyses of the recognition of a bulk CD4 T-cell line using several recombinant RLakt proteins suggested the presence of multiple CD4 T-cell epitopes in the molecule. However, cloning from a bulk CD4 T-cell line resulted in only two clones from 200 wells seeded at three cells per well, and those two CD4 T-cell clones recognized the same epitope peptide in RLakt. The epitope peptide was 14-mer p12-25, AYREETLSIIPGLP, and its recognition was H-2IA(d)-restricted. This sequence overlapped with the CD8 T-cell epitope pRL1a in its N-terminal 5 amino acid residues. The relationship of the epitope to the pRL1a peptide predominantly recognized by CD8 CTL suggests that the 14-mer epitope is predominantly recognized by CD4 T-cells.

Phenotype and natural killer cell sensitivity of a radiation-induced acute T-cell leukaemia (Roser leukaemia) in PVG rats.

A radiation-induced T-cell leukaemia [Roser leukaemia (RL)] in the rat was conditioned for growth in vitro by repeated in vivo-in vitro passages. This in vitro cell line, termed RL-T, maintained its leukaemia-inducing property when transferred to syngeneic PVG rats. It expresses several T-cell markers and the T-cell alpha/beta receptor-CD3 complex. RL-T, furthermore, expresses major histocompatibility complex (MHC) I antigens, both classical (RT1.A) and nonclassical (RT1.C), which makes it susceptible to killing by alloreactive natural killer cells in vitro.

Analysis of CD8 T-cell response by IFNgamma ELISPOT and H-2L(d)/pRL1a tetramer assays in pRL1a multiple antigen peptide-immunized and RL male 1-bearing BALB/c and (BALB/c x C57BL/6) F(1) mice.

We previously identified an H-2L(d)-binding peptide pRL1a (IPGLPLSL) on RL male 1 that is predominantly recognized by cytotoxic T-lymphocytes (CTLs). MAP is a multibranched lysine core with antigenic peptides. Immunization of BALB/c mice with pRL1a MAP effectively induced pRL1a CTLs. Here, we demonstrate the presence of pRL1a-recognizing CD8(+) T-cells in pRL1a MAP-immunized and RL male 1-bearing BALB/c and (BALB/c x C57BL/6)F(1) mice by using IFNgamma ELISPOT and H-2L(d)/pRL1a tetramer assays. A few IFNgamma ELISPOTs and no tetramer-positive cells were detected ex vivo in spleen cells from BALB/c mice immunized with pRL1a MAP. After a single in vitro stimulation with RL male 1, 432 and 741 IFNgamma ELISPOTs/10(5) cells were detected and tetramer-positive CD8(+) T-cells occurred at relative frequencies of 5.7% and 30.8% in splenic CD8(+) T-cells from mice that had been doubly and triply immunized, respectively, against pRL1a MAP. Tetramer-positive cells displayed two distinct cell populations, CD62L(low) and CD62L(high). Secondary in vitro stimulation expanded CD62L(high) cells more efficiently than CD62L(low) cells. Furthermore, a higher frequency of IFNgamma-producing and tetramer-positive CD8(+) T-cells was detected ex vivo in RL male 1-bearing semi-allogeneic (BALB/c x C57BL/6)F(1) than in BALB/c mice on day 14 after tumor inoculation.

[Spontaneous leukosis as a model for an investigation of low and very low physical and physico-chemical effects on oncological process]. / Spontannyi leikoz -- model' dlia izucheniia éffektov malykh i sverkhmalykh doz fizicheskikh i fiziko-khimicheskikh vozdeistvii na opukholevyi protsess.

Kinetic investigation of spontaneous leukosis in AKR mice have been carried in connection with a number of indices: changes in the mass of principal organs of the immune systems (thymus, spleen, lymphatic nodes), liver, alterations of haematological data (the sum of leukocytes, the percentage composition of blood cells, the quantity of undifferentiated cells), changes of physico-chemical conditions in cells (NMR-investigation). The dynamics of some of these indices and also life-spans of animals with leukosis after irradiation with doses 1.2-2.4 cGy (dose-rate 0.6 cGy/day) have been investigated. The enhancement of the frequency of leukosis and shortening the average and maximum life-spans of irradiated mice has been found.

The combination of chemotherapy and systemic immunotherapy with soluble B7-immunoglobulin G leads to cure of murine leukemia and lymphoma and demonstration of tumor-specific memory responses.

Major mechanisms underlying poor immune responses to autologous tumor-associated antigens are overwhelming tumor kinetics and the absence of effective T-cell costimulation by antigen-presenting cells. To address these issues, leukemia and lymphoma mice were treated with the combination of chemotherapy and systemic immunotherapy with recombinant soluble murine B7-immunoglobulin G (IgG) molecules. In this report, 3 murine models were used, a radiation-induced SJL acute myeloid leukemia, a transplantable spontaneous SJL lymphoma, and the C57BL/6 EL-4 thymic lymphoma. Various treatment modalities were evaluated: single treatments with either B7-IgG or chemotherapy as well as combination therapies. The results demonstrate the following: (1) in all tumor models, the combination of chemotherapy and soluble B7-IgGs is more potent than either therapy alone, leading to cure of tumor-bearing animals; (2) the therapeutic responses are T-cell-dependent, because combined therapy is not efficacious in severe combined immunodeficient mice; (3) the rejection of tumor cells leads to the development of tumor-specific immunity, because cured mice are immune to the rejected tumor but not to a different syngeneic tumor; and (4) (51)Cr release assays show that rejection of tumor cells leads to the development of very potent tumor-specific cytotoxic T-lymphocyte activity. On the basis of these results, it is proposed that chemotherapy-mediated tumor reduction, together with consequent augmented tumor-antigen presentation to activated T cells, are primary mechanisms leading to curative responses. The safety profile of the B7-IgG fusion proteins and their synergy with chemotherapy strongly suggest that the combination regimen is a promising strategy in cancer treatment.

ELISPOT cloning of tumor antigens recognized by cytotoxic T-lymphocytes from a cDNA expression library.

The methodology of cloning genes coding for antigens recognized by T-cells from cDNA expression libraries was improved technically by using enzyme-linked immunospot (ELISPOT) assays instead of enzyme-linked immunosorbent assays (ELISA) or bioassays to detect cytokines produced by T-cells in response to antigens. Combining large and small scale ELISPOT assays for expression cloning has the following advantages compared to conventional cDNA expression cloning: i) the number of recombinant plasmids which can be screened is greater than 10,000 per well in a 24-well plate in a large scale ELISPOT assay compared to fewer than 100 per well in a 96-well plate in an IFN-gamma ELISA or a TNF-alpha bioassay; ii) the total number of recombinant plasmids which can be screened in a routine assay is 2 x 10 (5) in only one 24-well plate in a large scale ELISPOT assay compared to 1 x 10 (5) in ten 96-well plates in an IFN-gamma ELISA or a TNF-alpha bioassay. Thus the screening efficiency of large scale ELISPOT cloning is approximately 200 times that of conventional expression cloning approaches. The efficiency of the method was confirmed by detecting the model gene RLakt from a cDNA library of a murine leukemia RL male 1.

Induction of CTL responses by simultaneous administration of liposomal peptide vaccine with anti-CD40 and anti-CTLA-4 mAb.

Activation of APC via CD40-CD40 ligand pathway induces up-regulation of costimulatory molecules such as B7 and production of IL-12. Interaction between B7 on APC and CD28 on naive T cells is necessary for priming the T cells. On the other hand, interaction between B7 on APC and CTLA-4 on activated T cells transduces a negative regulatory signal to the activated T cells. In the present study, we attempted to generate tumor-specific CTL by s.c. administration of antigenic peptides encapsulated in multilamellar liposomes (liposomal peptide vaccine) with anti-CD40 mAb and/or anti-CTLA-4 mAb. Liposomal OVA257-264 and anti-CD40 mAb or anti-CTLA-4 mAb were administrated to C57BL/6 mice and the splenocytes were cocultured with OVA257-264 for 4 days. The splenic CD8+ T cells showed a significant cytotoxicity against EL4 cells transfected with cDNA of OVA. In addition, administration of both anti-CD40 and anti-CTLA-4 mAb enhanced the CTL responses. Considerable CTL responses were induced in MHC class II deficient mice by the same procedure. This finding indicated that CTL responses could be generated even in the absence of Th cells. When BALB/c mice were immunized with pRL1a peptide that are tumor-associated Ag of RLmale symbol1 leukemia cells using the same procedure, significant CTL responses were induced and prolonged survival of the BALB/c mice was observed following RLmale symbol1 inoculation. These results demonstrate that anti-CD40 mAb and anti-CTLA-4 mAb function as immunomodulators and may be applicable to specific cancer immunotherapy with antitumor peptide vaccine.

Tumor rejection by in vivo administration of anti-CD25 (interleukin-2 receptor alpha) monoclonal antibody.

Immune regulation has been shown to be involved in the progressive growth of some murine tumors. In this study, we demonstrated that a single in vivo administration of an amount less than 0.125 mg of anti-CD25 interleukin 2 receptor alpha monoclonal antibody (mAb; PC61) caused the regression of tumors that grew progressively in syngeneic mice. The tumors used were five leukemias, a myeloma, and two sarcomas derived from four different inbred mouse strains. Anti-CD25 mAb (PC61) showed an effect in six of the eight tumors. Administration of anti-CD25 mAb (PC61) caused a reduction in the number of CD4+ CD25+ cells in the peripheral lymphoid tissues. The findings suggested that CD4+ CD25+ immunoregulatory cells were involved in the growth of those tumors. Kinetic analysis showed that the administration of anti-CD25 mAb (PC61) later than day 2 after tumor inoculation caused no tumor regression, irrespective of depletion of CD4+ CD25+ immunoregulatory cells. Two leukemias, on which the PC61-treatment had no effect, seemed to be incapable of eliciting effective rejection responses in the recipient mice because of low or no antigenicity.

Detecting the health risks of radiation.

Radiation can cause both non-stochastic (cell-killing) effects, leading to burns, epilation, immune system damage and lens opacities, and mutational or stochastic effects due to low dose damage to single cells. If the latter are followed by clone formation or fertilization, the mutants are not recognized by the immune system, and there is no competing cause of death, cancer or leukaemia can result. These effects did not become public knowledge until after the A-bombings of Hiroshima and Nagasaki. Subsequent analysis of the data on A-bomb survivors suggests, contrary to official views, that the immune system has a complex role in the aetiology of cancer and leukaemia, and that the A-bomb survivors were unusually resistant to the harmful effects of the bombings. These findings require the re-evaluation of the effects of low-level radiation, which has increased with the growth of the nuclear industry, both civil and military.

Expression of multiple unique rejection antigens on murine leukemia BALB/c RLmale symbol1 and the role of dominant Akt antigen for tumor escape.

Using the pRL1a Ag-loss RLmale symbol1 tumor variant cell line RM2-1, we demonstrated the presence of tumor Ags other than pRL1a that were recognized by CTLs on RLmale symbol1 cells. Semiallogeneic CB6F1 or syngeneic BALB/c CTLs generated against RM2-1 lysed RM2-1 and RLmale symbol1 cells to a similar extent, but no killing was observed with any other tumor or normal cells examined. Clonal analysis and sensitization with reversed phase-HPLC fractions revealed that there were Dd- and Ld-binding peptides recognized by RM2-1 CTLs. Lysis by bulk CTLs stimulated against RLmale symbol1 and limiting dilution analysis suggested that the pRL1a peptide was dominantly recognized to the RM2-1 peptides by CTLs on RLmale symbol1 cells. The rejection response against the parental RLmale symbol1 tumor was much less than that against RM2-1 cells in either CB6F1 or BALB/c mice, suggesting that the presence of altered Akt molecules from which the dominant pRL1a peptide was derived inhibited the rejection response against RLmale symbol1. Depletion of CD4 T cells caused the regression of RLmale symbol1 at the doses in which the tumor grew in untreated mice. The generation of pRL1a CTLs was inhibited in RLmale symbol1-bearing mice. Thus, immunoregulatory CD4 T cells were most likely activated by the altered Akt molecules and inhibited the efficient generation of CTLs against the dominant pRL1a Ag in RLmale symbol1.

Inhibition of T-cell acute lymphoblastic leukemia proliferation in vivo by re-expression of the p16INK4a tumor suppressor gene.

T-cell acute lymphoblastic leukemia (T-ALL) is characterized by the presence of differentiation-inhibited pro- and pre-T-cell blasts. The p16INK4a tumor suppressor gene has been shown to be frequently deleted in human T-ALL cases. Deletion of p16INK4a may be associated with poor prognosis and relapse of the disease. Radiation-induced murine T-ALL in C57B1/6 mice shares pathogenetic and molecular characteristics with the human disease. We used the murine disease as a model to study the status of the INK4/ARF gene locus and to examine the effect of p16INK4a-re-expression in T-ALL cells on their leukemic potential in vivo. In 9 of 17 radiation-induced murine T-ALL cell lines, the p16INK4a protein was not expressed as determined by immunoblotting. Southern blot analysis revealed homozygous deletions of the p16INK4a gene locus in three of the nine lines, along with the genes encoding p15INK4b and p19ARF. Transduction of p16INK4a-negative T-ALL lines with retrovirus encoding p16INK4a significantly inhibited their in vitro proliferation by inducing G1-arrest. Importantly, re-expression of p16INK4a in p16INK4a-negative T-ALL cells obliterated the induction of lethal disseminated leukemia in syngeneic mice. This is the first demonstration that re-establishment of p16INK4a expression is critical for in vivo growth regulation of T-ALL cells.

Immunotherapeutic potential of dendritic cells generated in long-term stroma-dependent cultures.

Long term cultures (LTC) producing dendritic cells (DC) have been established from spleen. A well developed stromal cell layer supported production of DC in numbers suitable for experimentation. Cells had obvious membrane pseudopodia and could be collected from culture every 2-3 days. Large cells produced in LTC stained with fluorescently labelled monoclonal antibodies specific for DC such as 33D1, and M1/70 which is specific for DC and myeloid cells. These staining patterns confirmed the presence of DC within the LTC population. LTC-DC were tested and shown capable of migration in vivo in B10.A(2R) mice following footpad inoculation. Most cells entered the spleen and a small number entered popliteal lymph node. LTC-DC have migratory capacity comparable with control spleen lymphocytes. LTC-DC were tested for capacity to induce an anti-tumour immune response after exposing cells to tumour cell membranes. LTC-DC pulsed with BL/VL3 tumour antigens were able to induce a BL/VL3-specific primary cytotoxic T lymphocyte (CTL) response detectable in popliteal lymph nodes and spleen of C57BL/6J mice within 6 days of priming. BL/VL3 tumour cells grew in sublethally irradiated C57BL/6J mice giving 100% mortality. Adoptive transfer of spleen cells from mice given BL/VL3 antigen-pulsed LTC-DC, two weeks previously, significantly slowed the growth of BL/VL3 tumour cells in mice. DC produced in LTC can function as antigen presenting cells (APC) when adoptively transferred into animals. Their capacity to migrate effectively, to induce a CTL response and to reduce tumour load suggests that DC grown using this in vitro system may have valuable clinical potential in humans.

Vaccination with multiple antigen peptide as rejection antigen peptide in murine leukemia.

pRL1a (IPGLPLSL) is the Ld-binding tumor rejection antigen peptide recognized by CTLs on BALB/c radiation leukemia RL(male)1. We demonstrated that in vivo and in vitro sensitization with pRL1a multiple antigen peptide (MAP), but not with the pRL1a peptide itself, generated pRL1a-specific CTLs in the spleen cells of BALB/c mice. No enhancement of cytotoxicity was observed by emulsifying pRLla MAP in incomplete Freund's adjuvant or in complete Freund's adjuvant for in vivo sensitization. Selective depletion of CD4+ T cells in mice by treatment with anti-L3T4 (CD4) monoclonal antibody and that of macrophages by treatment with carrageenan on in vivo sensitization with pRL1a MAP abrogated CTL generation. The findings suggest that CD4+ T cells and antigen-presenting cells were necessary for the in vivo priming of CD8+ T cells with pRL1a MAP. Furthermore, we demonstrated that in vivo sensitization of BALB/c mice with pRL1a MAP, but not with pRL1a peptide, showed an inhibitory effect on RL(male)1 tumor growth. No growth-inhibitory effect was observed on control RVA, RVD, or Meth A tumors.

A new immunobiological view of radiation-promoted lymphomagenesis.

Whole-body irradiation produces T-cell leukaemias/ lymphomas (TCL) in some strains of inbred mice in an X-ray dose-related manner. Radiation biologists have related the rapid "initiation' and early appearance of preleukaemic cells in these mice to unrepaired DNA damage inflicted by radiation. Following initiation, radiation-altered thymic differentiation fosters multi-step transformation changes in proto-oncogenes and suppressor gene expression in individual clones of non-invasive preleukaemia cells as they progress to malignancy. The malignant clones arising from small numbers of initiated preleukaemia thymocytes become fully transformed only after several more months to a year after irradiation in those strains of mice which develop T-cell lymphomas. When the RFM mouse was subjected to sublethal whole-body X-ray, only 50% of the mice developed TCL by 6 months, yet nearly all developed preleukaemia thymocytes. The T-cell-mediated immune response of the irradiated host has never been substantiated to contribute to malignant TCL development. Until recently, X-ray-induced TCL were not known to carry common tumour rejection antigens TATA. However, several studies have revealed that both preleukaemia cells and fully malignant TCL express an immunogenic, common oncofoetal glycoprotein, termed 44kD OFA. OFA-activated memory CD4 Tm and CD8 Ten. T-effector cells in irradiated mice expressing OFA. As most irradiated RFM mice exhibit preleukaemia thymocytes yet only half develop tumours, this finding implicates active host T-cell effector responses in X-ray-initiated tumorigenesis. Further, the recent discovery of OFA-specific CD8 Ts clones in irradiated mice, which inhibited cytotoxicity of CD8 clones to OFA or TSTA, may explain which mice develop T-cell lymphomas.

Production of murine leukemia RLmale1 rejection antigen peptide pRL1a by proteolysis of natural precursor pRL1b.

In this study, we demonstrated that NH2-terminal Ser and Ile residues of pRL1b (SI-pRL1a) (SIIPGLPLSL) are not involved in the recognition by RLmale 1-specific cytotoxic T lymphocyte. The sensitization activity observed with pRL1b (SI-pRL1a) was not greater than that of peptides substituted with irrelevant amino acids at these positions. In serum-free medium, pRLla retained sensitization activity, but pRL1b (SI-pRL1a) did not. Furthermore, addition of bestatin to serum-containing medium blocked sensitization by pRL1b (SI-pRL1a). On the other hand, the addition of captopril enhanced it, probably by inhibiting the degradation of pRL1a by ACE. pRL1a-D peptide with D-Ile in place of the L-Ile residue of pRL1a (IPGLPLSL) showed sensitization, but SI-pRLla-2,3D peptide, which has D-Iles in place of the L-Ile residues of pRLlb (SI-pRL1a), and which was not cleaved between the two D-Iles, did not. The findings suggest that pRL1a is the antigenic peptide bound to L(d) molecules and pRL1b (SI-pRL1a) peptide is its natural precursor, which generates pRL1a via proteolysis.

A hematopoietic organ-specific 49-kD nuclear antigen: predominance in immature normal and tumor granulocytes and detection in hematopoietic precursor cells.

A 49-kD protein was specifically detected in hematopoietic organs by Western blotting with a novel mouse monoclonal antibody (B92) raised against stromal cells. The protein was found in the immunizing cells using a sensitive method. However, its detection in the bone marrow by the B92 antibody seemed to stem from the abundance of p49 in immature cells of the myeloid lineage. Study of the bone marrow following in vivo irradiation or 5-fluorouracil (5-FU) treatment, in vitro culture with differentiation-inducing factors and long-term culture, and cell sorting all pointed in the same direction: the protein was found in early myeloid cells and in hematopoietic precursor cells. These results were in accordance with the specific presence of p49 in primary radiation-induced myeloid leukemia and its absence in spontaneous B lymphoma. Immunofluorescent staining using B92 antibody detected a nuclear antigen forming a dotted pattern in early myeloid cells and day 12 colony-forming units-spleen (CFU-S). Nuclear localization of p49 was further demonstrated by subcellular fractionation followed by Western blotting. We thus identified a nuclear protein that within the hematopoietic population is detected in hematopoietic precursor cells, predominates in early myeloid cells, and is reduced following differentiation. These properties imply that p49 might be involved in the regulation of hematopoietic cell growth or differentiation.