Michael Bennett

Learning deficits occur in young mice following transfer of immunity from senescent mice

The extent to which immune processes contribute to senescence-related neurological/behavioral impairment was examined using an adoptive transfer procedure. C57BL/6 mice aged 22 to 24 months showed impaired ability for acquisition of an active avoidance response when compared with younger mice aged 3 months. An immunofluorescence assay of the sera of these mice indicated that only sera from the senescent mice reacted with brain antigen. When tested three months following irradiation and receipt of bone marrow/spleen cell suspensions from senescent mice, young mice showed senescence-like serum-brain reactivity and declines in their abilities to acquire learning. Young control mice receiving cell suspensions from age-matched donors showed no evidence of serum-brain reactivity or learning deficits, suggesting that impaired learning was related to acquisition of aged immunity and not a nonspecific effect of the transfer procedure. These findings indicate that immune processes may be involved in the etiology of senescence-related neurological/behavioral dysfunctions.

Marrow-dependent cell function in early stages of infection with Listeria monocytogenes.

Abstract Mice were infected with either Listeria monocytogenes (LM) or Yersinia pestis EV 76 stain ( YP ), which are facultative intracellular and extracellular organisms, respectively. Bacterial growth in spleen was determined at various intervals following challenge, focusing particularly on the critical period prior to the emergence of specific immunity. Natural resistance to LM during the first 2 days was diminished by treatment of adult mice with 80 Sr or silica particles, but not by treatment with lethal total-body irradiation, cortisol, or cyclophosphamide (CY). Early stages of resistance to YP were unaffected by 80 Sr, but were reduced by lethal total-body irradiation, silica particles, cortisol, and (CY). Infant mice manifested no resistance comparable to that of adults against LM prior to 19 days of age, whereas resistance against YP was attained by 14 days of age. The data are consistent with the hypothesis that marrow-dependent (M) cells function in host defense against early stages of infection with LM but not with YP.

Inhibition of an in vitro antibody response by a suppressor cell in normal bone marrow

Abstract Murine bone marrow cells can suppress the in vitro primary antibody response of normal spleen cells without apparent cytotoxicity. The bone marrow cells suppress the response to both T-dependent (SRBC) and T-independent (DNP-Ficoll) antigens. When bone marrow cells are fractionated on a sucrose density gradient, the suppressive activity is found in the residue rather than the lymphocyte fraction. The suppressive activity is either unaffected or enhanced by treatment with anti-T- and anti-B-cell serums. Pretreatment of mice with phenylhydrazine which reduces the number of pre-B cells did not reduce the suppressive activity of their bone marrow cells. Suppressive activity is abolished by irradiation of the marrow cells in vitro with 1000 R prior to assay. The activity is present in the marrow of thymus deficient (nude) mice, infant mice, and mice which have been made polycythemic by transfusion. Furthermore, the suppressor cell can phagocytize iron carbonyl particles, is slightly adherent to plastic and Sephadex G-10, and can bind to EA monolayers. We conclude that the suppressor cell is not a mature lymphocyte or granulocyte nor a member of the erythrocytic series, but is likely to be an immature cell possibly of the myeloid series. We speculate on the physiologic role of this cell.

Extended self-renewal capacity of pluripotent hemopoietic stem cells: Association with persistent friend spleen focus-forming virus

The pluripotential hemopoietic stem cells (CFU-S) of genetically resistant Fv2rr adult C57BL/6 (B6) mice can be persistently infected by Friend virus (FV) when exposed to defective spleen focus-forming virus (SFFV) and helper virus (LLV) at the time of transplantation into heavily irradiated syngeneic recipients (that is, B6 leads to B6 isologous chimeras). Whereas normal and LLV+ marrow were depleted of CFU-S after three serial transplantations at 14-day intervals, SFFV+ donor marrow exhibited prolonged self-renewal capacity. SFFV+ CFU-S from B6. Fv2rr chimeric mice gave rise to normal erythroid and myeloid progenitor cells and were easily detected and quantified over 17 serial marrow transfers equivalent to 260 cumulative days. Marrow cellularity on day 14 of each transfer remained constant during the entire transplantation time. When SFFV fell below detectable levels at passage 15, CFU-S self-renewal exhibited rapid and total decline. Since the frequency of LLV-infected cells in late marrow transfers rose during the period of CFU-S decline, we conclude that SFFV is directly associated with the triggering of CFU-S self-renewal. It is also suggested that this proliferative event may be a prerequisite for the development of FV-induced leukemia.

F1 hybrid resistance to BN rat myelogenous leukemia parallels resistance to transplantation of normal BN bone marrow.

Abstract Short-term BN bone marrow engraftment, and survival after injection of BN myelogenous leukemia were measured in three different F1 hybrid strains which had BN as one parent. The two hybrids that were resistant to BN bone marrow were resistant to BNML, while the hybrid strain that accepted BN marrow died earliest after BNML injection. The results support the hypothesis that BN bone marrow and BNML share antigens that can lead to rejection of tissue grafts. The importance of such presumptive bone marrow alloantigens in the treatment of myelogenous leukemia by bone marrow transplantation is discussed.

Bone-marrow-cell grafts involving the H-2D and H-2L mutant haplotypes.

TwoH-2d mutants,H-2dm2 (H-2L loss mutation) andH-2dm1 (gainplus-loss mutation involving bothH-2L andH-2D) were evaluated for any change in the immunogenicity of marrow stem cells. Grafts of 2 or 4 × 106 BALB/c(C) or BALB/c-H-2dm2 (C-H-2dm2) marrow cells were accepted by lethally irradiated B10.D2(H-2d) recipients and were rejected by irradiated B10(H-2b) recipients. Moreover, both (B6 × C)F1 and (B6 × C-H-2dm2)F1 mice, as irradiated recipients, resisted the growth of parental-strain B6(H-2b) marrow cells but accepted grafts from C or C-H-2dm2 parental-strain donors. Thus, theH-2 mutation involvingH-2L but notH-2D did not affect the expression ofH-2d-associated Hemopoietic or Hybrid(Hh) antigens of marrow stem cells. Grafts of 2 to 8 × 106 B10.D2 or B10.D2-H-2dm1 marrow cells were rejected by B10.BR(H-2k) and B6 hosts and were accepted by B10.D2 hosts. However, B10.D2-H-2dm1 marrow cells grew to a much greater extent than B10.D2 cells in irradiated (B6 × B10.D2)F1 or (B6 × B10.D2-H-2dm1)F1 host mice. Therefore, theH-2dm1 mutation has altered the expression of Hh antigens at least quantitatively, resulting in a relative loss of “hybrid resistance” with the retention of Hh determinants recognized by allogeneic recipient mice which are notH-2d. Since the Hh determinants of B10.D2 marrow cells have been mapped 16 cM to the right ofH-2, this mutation atH-2D/H-2L may have affected a regulatory gene.

Graft-versus-host reactions in mice. II. Antagonism between marrow and thymus cells☆

Abstract Irradiated (600 R) F1 hybrid mice were grafted with parental thymus and/or marrow cells, and survival time, proliferation, and erythropoiesis in spleen, and content of bone marrow and spleen erythropoietic progenitor cells were determined. Thymus cells alone effected a fatal graft-versus-host reaction (GVHR), and survival times were inversely related to inoculum size. Marrow syngeneic with thymus antagonized this lethal effect. Synergistic splenic proliferation by marrow-thymus cell grafts was observed to be due to enhancement of erythropoiesis and not GVHR. Marrow and spleen progenitor cells were suppressed by grafts of thymus cells alone, but were replenished by marrow-thymus cell mixtures, and were of donor origin. Marrow cells allogeneic with thymus cells failed to protect, to proliferate synergistically, or to replenish progenitor cells. A regimen of cortisol that suppresses antibody formation but not erythropoiesis did not prevent marrow-thymus cell antagonism. Thus, marrow syngeneic with thymus cells antagonizes the GVHR by supplying progenitor cells which are not subject to attack but are stimulated by a small and decreasing host stem cell pool.

Genetic Resistance to Friend Virus-Induced Erythroleukemia and Immunosuppression

The Friend virus (FV) is a complex of a replication-defective spleen focus forming virus (SFFV) and its helper lymphatic leukemia virus (LLV) (Steeves et al. 1971; Troxler et al. 1977). Infection of susceptible adult mice with FV leads to a rapidly developing erythroleukemia accompanied by extensive viral replication in the spleen and profound suppression of humoral and cellular immunity (Bennett and Steeves 1970; Mortensen et al. 1974). Within 7–9 days after infection with small doses of FV, the spleen becomes enlarged due mainly to focal proliferation of neoplastic erythroid cells. This results in the characteristic appearance of raised yellowish foci when such spleens are fixed in Bouin’s solution (Axelrad and Steeves 1964). As the disease progresses, both liver and spleen enlarge, but thymus and lymph nodes remain relatively unaffected. One variant of FV, isolated initially by Mirand (Mirand et al. 1968), leads to a progressive increase in hematocrit (polycythemia), and eventually most mice die, often with splenic rupture, in 30–60 days. Several H-2-linked and nonlinked genes which regulate the effects of FV have been described. The Fv-1 locus controls host resistance to the helper virus, Fv-1-mediated resistance is not unique to Friend LLV but rather a general phenomenon seen with respect to a variety of murine leukemia virus (MuLV) isolates (Pincus et al. 1971). Two alleles designated as Fv-1 n and Fv-1 b have been described and these define the N or B tropism of MuLV. The Fv-1 gene regulates viral replication, and it is possible to overcome Fv-1 resistance by utilizing laboratory-derived NB-tropic viruses.

Mechanism of genetic resistance to immune suppression by Friend leukemia virus: the role of marrow-dependent cells.

The Friend virus (FV) is a complex of a defective Friend spleen focusforming virus (SFFV) and its helper lymphatic leukemia virus (MuLV-F) .l Infection of susceptible adult mice by FV leads to a rapidly developing erythroleukemia accompanied by extensive viral replication and profound suppression of humoral and cellular immunity.?. 3 These effects of FV are under host genetic control. The Fv-2 locus controls host resistance to F-SFFV. Adult homozygous resistant mice (Fv-2”) such as C57BL/6 (B6), BlO.D2n/Sn (B10.D2), and C58, are refractory to FV-induced malignant erythroblastosis,‘ and quite resistant to FV-induced immunosuppression.”, Since resistance to the erythroleukemic and to the immunosuppressive effects of FV seem to go hand-in-hand, an analysis of the mechanisms of genetic resistance to leukemia could be expected to give an insight into the mechanisms of resistance and susceptibility to immunosuppression. Therefore, as a first step in our investigations, we sought to analyze the mechanisms of in vivo resistance to erythroleukemia in Fv-2-resistant strains of mice.

Aging of Natural and Acquired Immunity of Mice. II. Decreased T Cell Responses to Syngeneic Tumor Cells and Parental-Strain Spleen Cells

Cytolytic T lymphocyte (CTL) functions were compared in mice between the ages of 2 and 30 months. The stimulator cells were H-2 allogeneic spleen or tumor cells, parental-strain spleen cells, or syngeneic tumor cells. Effector cells capable of lysing syngeneic tumor cells were shown to be T cells and not NK cells. The cell-mediated lympholysis (CML) responses by spleen cells of aged mice were near normal against H-2 allogeneic spleen or tumor cells but were defective against syngeneic tumor cells or parental-strain spleen cells. The defective syngeneic tumor CML response was observed at various responder:stimulator ratios and at various days of incubation. The defect was in the nonadherent, and not in the adherent, fraction of spleen cells. Suppressor cells were detected in spleens of 30 month, but not of 18 month old mice. Aged mice were more susceptible than young mice to small inocula of syngeneic C57BL EL-4 lymphoma cells. The immunogenicity of irradiated spleen cells of old mice had not changed for the F1 antiparent CML response. Splenic CML responses of young mice treated with 89Sr demonstrated a similar pattern, i.e., good responses to H-2 allogeneic stimulator cells but poor responses to syngeneic tumor cells or to parental-strain spleen cells. This loss of certain CTL functions influenced by marrow dependent cells can partially explain the increased susceptibility of old animals to tumors.