Lymphoid bone marrow cultures can reconstitute heterogeneous B and T cell-dependent responses in severe combined immunodeficient mice

Long-term lymphoid bone marrow cultures (LBMC) produce B lymphocytes and their precursors for several months in vitro. To assess their differentiative potential and determine their capacity to function as immune effectors, cells from the cultures were transplanted into mice with severe combined immune deficiency disease (SCID). SCID mice are deficient in T and B lymphocytes and are serum immunoglobulin (Ig) negative, but grafts of normal lymphoid precursors can expand and differentiate in them, thereby restoring immunocompetence. The results of these studies indicate that cells from LBMC are able to reconstitute splenic B lymphocytes in the SCID mice. Upon in vivo transfer, LBMC cells secreted Ig that displayed isotype distribution and a pattern of heterogeneity comparable with normal BALB/c mice, as determined by two-dimensional gel electrophoresis. The transplanted LBMC cells were functional, because reconstituted mice could respond to immunization with the T-independent antigen TNP-Ficoll. The results also indicate that cultured cells could reconstitute T cell activity in SCID mice. Splenocytes from approximately one-third of the recipients could generate a cytotoxic response to alloantigens after 5 days of sensitization in a mixed lymphocyte culture, and all reconstituted SCID mice could respond to immunization with the T cell-dependent antigen TNP-BSA. These results demonstrate that B cells, as well as T cell activity, are present in LBMC-reconstituted SCID mice, and show that LBMC cells have the capacity to mediate an immune response.     

Apparent T cell function of bone marrow cells from mice experiencing a graft-versus-host reaction.

The graft-versus-host (GVH) reaction, induced in adult F₁ mice by the injection of parental strain lymphoid cells (GVH mice), suppressed the in vitro plaque-forming cell (PFC) response to sheep erythrocytes (SRBC) of spleen cells obtained from the GVH mice (GVH-SC). In vitro restoration of the PFC response of GVH-SC was carried out employing a modified Marbrook culture chamber consisting of an inner culture compartment (IC) separated from an outer culture compartment (OC) by a cell-impermeable membrane. Thymus cells (TC) and lymph node cells (LNC) but not bone marrow cells (BMC) from normal mice placed in the IC restored the PFC response of GVH-SC cultured with SRBC in the OC. The restoring ability of TC and LNC was markedly reduced following treatment with anti-theta serum plus complement. BMC taken from GVH mice 3 or more days post-GVH induction (GVHBMC) and placed in the IC restored the PFC response of GVH-SC as well as TC and LNC. Treatment of GVH-BMC with anti-theta serum plus complement did not affect their restoring ability; furthermore, the number of theta-bearing cells in the bone marrow did not increase as a consequence of the GVH reaction. Two possible explanations are proposed for the T-like function of GVH-BMC.     

Cytotoxic T cell response and thymic hormonal dysfunction in graft-vs-host mice

As an approach to dissect complex mechanisms that lead to graft-vs-host (GvH)-associated immune disorders, we have compared the splenic cytotoxic T lymphocyte (CTL) response and thymic hormonal function in nonirradiated F1 hybrid mice injected with parental spleen cells. Thymic secretory function was studied by the determination of serum thymulin levels, and the number of thymic epithelial cells containing thymulin as assessed by indirect immunofluorescence with the use of an anti-thymulin monoclonal antibody. In addition, the epithelial cell network was analyzed with an anti-keratin serum, and the general histology pattern was studied by conventional histologic methods. An initial analysis was performed on day 15, which was characterized by CTL suppression mediated by parental suppressor T cells. No thymic abnormalities were detected at this time. By day 45 after GvH induction, active CTL suppression had decreased, and GvH was associated with a progressive decline in thymic hormonal function. Finally, by day 60 and thereafter, F1 GvH mice recovered normal in vitro CTL responsiveness, which contrasted with profound alterations of the epithelial cell network and severely reduced serum thymulin levels. This hormonal dysfunction was shown to be directly associated with a reduction in the number of thymulin-containing cells. Moreover, no anti-thymulin auto-antibodies could be detected. The results are discussed with respect to the role of thymic hormonal dysfunction in the modulation of F1 CTL responses observed during the course of a GvH reaction, and the additional analogy of this GvH model with human immunodeficiency.     

Suppressor T cells arising in mice undergoing a graft-vs-host response.

We investigated the ability of mice to generate antibody-forming cells when undergoing a graft-vs-host reaction. (C57BL/6 X DBA/2)F1 mice (BDF1) injected with C57BL/6 spleen cells generated suppressor T cells which inhibit antibody synthesis by BDF1 spleen cells in vitro. These T cells arose from the donor inoculum. They differ from helper T cells in size and they act directly on antigen reactive B cells. The suppressor T cells were specifically directed against components of the H-2 region of the reciprocal parental strain (DBA/2 = H-2d) in the hybrid F1 mouse.     

Anti-bacterial immunity to Listeria monocytogenes in allogeneic bone marrow chimera in mice

Protection and delayed-type hypersensitivity (DTH) to the facultative intracellular bacterium Listeria monocytogenes (L.m.) were studied in allogeneic and syngeneic bone marrow chimeras. Lethally irradiated AKR (H-2k) mice were successfully reconstituted with marrow cells from C57BL/10 (B10) (H-2b), B10 H-2-recombinant strains or syngeneic mice. Irradiated AKR mice reconstituted with marrow cells from H-2-compatible B10.BR mice, [BR----AKR], as well as syngeneic marrow cells, [AKR----AKR], showed a normal level of responsiveness to the challenge stimulation with the listeria antigens when DTH was evaluated by footpad reactions. These mice also showed vigorous activities in acquired resistance to the L.m. By contrast, chimeric mice that had total or partial histoincompatibility at the H-2 determinants between donor and recipient, [B10----AKR], [B10.AQR----AKR], [B10.A(4R)----AKR], or [B10.A(5R)----AKR], were almost completely unresponsive in DTH and antibacterial immunity. However, when [B10----AKR] H-2-incompatible chimeras had been immunized with killed L.m. before challenge with live L.m., these mice manifested considerable DTH and resistance to L.m. These observations suggest that compatibility at the entire MHC between donor and recipient is required for bone marrow chimeras to be able to manifest DTH and protection against L.m. after a short-term immunization schedule. However, this requirement is overcome by a preceding or more prolonged period of immunization with L.m. antigens. These antigens, together with marrow-derived antigen-presenting cells, can then stimulate and expand cell populations that are restricted to the MHC (H-2) products of the donor type.     

Use of lymphokine-activated killer cells to prevent bone marrow graft rejection and lethal graft-vs-host disease

Prompted by our recent finding that lymphokine-activated killer (LAK) cells mediate both veto and natural suppression, we tested the ability of adoptively transferred LAK cells to block two in vivo alloreactions which complicate bone marrow transplantation: resistance to transplanted allogeneic bone marrow cells, and lethal graft-vs-host disease. Adoptive transfer of either donor type B6D2 or recipient-type B6 lymphokine-activated bone marrow cells, cells found to have strong LAK activity, abrogated or inhibited the resistance of irradiated B6 mice to both B6D2 marrow and third party-unrelated C3H marrow as measured by CFU in spleen on day 7. The ability of lymphokine-activated bone marrow cells to abrogate allogeneic resistance was eliminated by C lysis depletion of cells expressing asialo-GM1, NK1.1, and, to a variable degree, Thy-1, but not by depletion of cells expressing Lyt-2, indicating that the responsible cells had a LAK cell phenotype. Similar findings were obtained by using splenic LAK cells generated by 3 to 7 days of culture with rIL-2. Demonstration that allogeneic resistance could be blocked by a cloned LAK cell line provided direct evidence that LAK cells inhibit allogeneic resistance. In addition to inhibiting allogeneic resistance, adoptively transferred recipient-type LAK cells prevented lethal graft-vs-host disease, and permitted long term engraftment of allogeneic marrow. Irradiation prevented LAK cell inhibition of both allogeneic resistance and lethal graft-vs-host disease. These findings suggest that adoptive immunotherapy with LAK cells may prove useful in preventing graft rejection and graft-versus-host disease in human bone marrow transplant recipients.     

Functional T cell deficits after bone marrow transplantation across minor histocompatibility barriers: effects of graft-vs-host disease on precursor frequency of reactive cells

We have studied T cell responses in mice transplanted with bone marrow from H-2-identical, minor histocompatibility loci-nonidentical donors (B10.BR----CBA) in which graft-vs-host disease is induced by the addition of donor T cells. T cell responses to mitogen were examined both in high density, conventional bulk cultures and by limiting dilution analysis. Long-lasting deficits in the frequency of functional T cells were observed, for both IL 2-producing and cytotoxic cells, in proportion to the severity of the graft-vs-host disease induced. These deficits did not reflect a corresponding loss of Thy-1+ cells nor a loss of function in conventional cultures in mice studied at later times after bone marrow transplantation. These deficits in reactive cells are not completely correctable with IL 2, and provide further insight into the nature of T cell reconstitution of the immune system after bone marrow transplantation.     

Development of immunity in human severe primary T cell deficiency following haploidentical bone marrow stem cell transplantation

Recent advances in the prevention of graft-vs-host disease (GVHD) have allowed the use of haploidentical bone marrow cells for correction of lethal genetic defects of the immune system. Sequential analyses of blood lymphocyte phenotypes and functions were done before and after transplantation of haploidentical marrow stem cells into 17 infants with severe primary T cell deficiencies. The marrow was depleted of post-thymic T cells and most other mature marrow cells by soy lectin agglutination and sheep erythrocyte rosetting. The studies were performed to define the time course and extent of appearance of immune function, and to identify factors leading to resistance to engraftment. No pretransplant immunosuppression was used. T cell function was detected between 34 and 287 days after transplantation, but a sharp rise usually occurred between 84 and 115 days, and normal function was reached between 113 and 210 days. Fifteen of the patients are alive from 6 to 41 mo post-transplantation, 12 have improved or have normal T lymphocyte function, and nine have proven T cell chimerism. Increased immunoglobulins of several isotypes have been noted in 11 patients and specific antibodies in seven patients, although B cell chimerism has been detected in only one patient. B cell function required 2 to 2.5 yr for normalization. No GVHD occurred in 14 patients, and the other three had only transient mild skin rashes. Two patients died of viral infections. Failure to engraft was correlated with some pre-transplant lymphocyte responses to mitogens and allogeneic cells (three cases), but not with the presence of pre-transplant natural killer cell function (five cases) nor with the presence of purine salvage pathway enzyme deficiencies (four cases). The latter, however, was associated with poor lymphoid function in two patients. These studies indicate that the thymic microenvironment of most infants with severe combined immunodeficiency disease is capable of differentiating donor stem cells to mature and functioning T lymphocytes which can cooperate with apparently normal host B cells for antibody production.     

Defective thymic education of L3T4+ T helper cell function in graft-vs-host mice

Our study investigates the effect of a prior graft-vs-host (GVH) reaction on the subsequent ability of irradiated, bone marrow-re-populated mice to develop T cell function. The results indicate that such GVH-bone marrow transplanted (BMT) mice do not generate CTL responses to trinitrophenyl-modified syngeneic cells (TNP-self), but do generate strong CTL activity to H-2 alloantigens. This selective deficiency in TNP-self CTL response potential appeared as early as 10 days after GVH, and required both L3T4+ and Lyt-2+ donor T cells. The in vitro addition of either soluble Th factors or L3T4-enriched spleen cells from normal mice circumvented the defect in the TNP-self response in GVH-BMT mice. These results indicate that T effector function was not defective, and instead suggest a Th defect. Cell depletion and antibody-blocking, as well as IL-2 production experiments, indicate that the Th defect was selective for L3T4+ Th population and not for Lyt-2+ Th population. This defect in L3T4 Th function is not accounted for by the approximate twofold reduction in L3T4 cell numbers in GVH-BMT mice, because IL-2 production and CTL generation to L3T4-dependent Ag were at least eightfold below control levels. Rather, defective L3T4 Th function appears to be the consequence of a GVH-induced defect in thymic maturation because the defect was corrected in vivo by a neonatal parental thymus graft before irradiation and bone marrow transplantation. This system may be useful for elucidating the role of the thymus in the maturation of Th cells. Our findings raise the possibility that impaired development of T cell function occurring in marrow grafted patients who have undergone a GVH reaction could be partly due to a GVH-induced thymic defect.     

Failure of NZB spleen to respond to prethymic bone marrow suppressor cells.

Mouse bone marrow contains theta-negative lymphocytes that can suppress an in vitro plaque response by spleen cells primed in vivo with burro red blood cells (BRBC). These bone marrow cells are radiosensitive and can be induced with thymosin fraction 5 or alpha 1 thymic peptides to express the theta antigen. Enrichment for these suppressor pre-T lymphocytes can be achieved by a one-step density centrifugation, macrophage depletion, or a combination of both procedures. NZB mice, which spontaneously develop an autoimmune disorder, have a suppressor abnormality revealed by this assay system. Upon analysis, they have normal BM pre-T suppressor cells but their spleen cells are refractory to the BM suppressor signal. NZB BM suppressor cells inhibit the response by DBA/2 spleen cells, but DBA/2 BM suppressor cells do not inhibit NZB spleen. This resistance to suppression is a property of the B cell fraction recovered from NZB spleen.     

Clonal abortion of bone marrow T cell precursors: T cells acquire specific antigen reactivity prethymically

Lethally irradiated (900 R) mice were reconstituted with bone marrow cells from syngeneic donors that had been tolerized 2 to 3 wk earlier to either DNP or TNP compounds. Five weeks after reconstitution, these animals were tested for their ability to mount a delayed hypersensitivity (DH) response to the tolerizing haptens. Recipient mice were specifically tolerant to the hapten that was used to induce tolerance in the marrow donor. Mixing experiments in which mice were reconstituted with marrow from DNP-tolerant and TNP-tolerant donors showed no indication of active suppression or effective antigen carry-over in this system. This observation held true even in experiments in which mice were reconstituted with a mixture of marrow from tolerant and normal donors at a ratio of 5:1. Thus the reduced responsiveness in recipient mice seemed to be due to the functional elimination of hapten-responsive T cell precursor (pre-T) clones. Recipient unresponsiveness was also shown to be MHC restricted. Maintenance of unresponsiveness appeared to be due to the restricted access of regenerating pre-T cell clones to the maturational influence of the recipient's thymus.     

Participation of cyclophosphamide-sensitive T cells in graft-vs-host reactions.

Cyclophosphamide (CY)3 is toxic for a population of mouse T cells which is active in graft vs host (GVH) responses. This observation contrasts with previous reports which indicate that treatment of mice with CY regimens, similar to those used in this study, enhances the reactivity of T cells which mediate delayed type hypersensitivity to sheep red blood cells. The GVH-inducing capacity of T cells is not altered by removal of B cells by nylon wool columns. We suggest that CY-sensitive T cells may be "regulatory cells," and that the effect they have depends on, among other things, the nature of the stimulating antigen to which the cells are responding and/or the assay used for study.     

Immunodominance in the graft-vs-host disease T cell response to minor histocompatibility antigens

Immunodominance controls the generation of CTL in the C57BL/6By (B6) anti-BALB.B H-2b-matched strain combination. Despite the potential of responding to numerous individual minor histocompatibility (H) Ag on BALB.B APC, the focus of the CTL response is largely specific for only a limited number of target Ag. These minor H Ag could be distinguished by their differential expression on a panel of target cells from the CXB recombinant inbred strains, the E, G, I, J, and K (all H-2b), which express different composites of the original BALB minor H Ag. A hierarchy was observed in which first-order immunodominant Ag were present on both CXBK and CXBG cells, whereas second-order dominant Ag were found on CXBE, CXBJ, and CXBI cells. To test whether immunodominance also plays a role in the development of lethal graft-vs-host disease (GVHD) directed to multiple minor H Ag, B6 T cells were transplanted along with T cell depleted bone marrow, to irradiated (825 rad) recipients of either the BALB.B or CXB recombinant inbred strains. The results indicate that a hierarchy of immunodominance does exist in GVHD, but it differs from that predicted from the in vitro CTL studies. GVHD was observed in BALB.B, CXBE, CXBI, and CXBJ recipients, but not in CXBG and CXBK recipients. Presensitization of B6 donor mice to CXBG or CXBK splenocytes 3 wk before transplant did not significantly increase the overall GVHD potential in the corresponding CXBG or CXBK recipients. Evidence for second-order immunodominance was provided by the transfer of CXBE T cells and ATBM to irradiated CXBG and BALB.B recipients with resultant, potent GVHD.     

Clonogenic stromal cell count in the bone marrow of mice

The number of fibroblast colonies in bone marrow cultures depends on FCFC concentration in explanted cells and FCFC cloning efficiency. For mouse bone marrow the efficiency of fibroblast colony formation increases in the presence of the feeder (irradiated bone marrow of spleen cells). Colony-stimulating feeder activity does not depend on the presence of phagocytic and stromal cells in the feeder cell population. Trypsinization of the bone marrow leads to the release of additional FCFC and the increase of their concentration in bone marrow cell suspensions.     

Reaction of bone marrow colony-forming cells in irradiated mice to phlogogenic factors]

The experiments on irradiated mice (600 and 800 r) demonstrated that under the influence of flogogenic factors the quantity of colonies in the spleen increases and their morphological structures change. It is suggested that under the action of the damaging agent the "hypothetic factor" which causes the pointed changes, is formed in the skin.     

Lymphokine-activated killer cells are generated before classical cytotoxic T lymphocytes after bone marrow transplantation in mice

Lymphokine-activated killer (LAK) cells are demonstrable within 2 wk after syngeneic or allogeneic (H-2-compatible) bone marrow transplantation in mice. Classical cytotoxic T lymphocytes (CTL) are not active until at least 4 wk after transplant. Both LAK cells and CTL bear the Thy-1 marker and do not possess the murine natural killer cell marker asialo GM.