Cells involved in the immune response. VII. The demonstration, using allotypic markers, of antibody formation by irradiation-resistant cells of irradiated rabbits injected with normal allogeneic bone marrow cells and sheep erythrocytes

Dual regulatory role of the thymus in the maturation of immune response in the rabbit

Rabbits thymectomized in early adulthood produced more antihapten antibody than sham-thymectomized controls after hyperimmunization with 2,4-dinitrophenyl bovine gamma globulin (DNP-BGG). The average associated constant of anti-DNP antibody produced by thymectomized animals was more than 10 times higher than that of the controls. Similar effects were obtained by extensive treatment of rabbits with antithymocyte serum (ATS) before and during the immunization with DNP-BGG. The results indicated that relative diminution of thymus-derived lymphocytes (T cells) resulted in a stimulation of antibody-forming cells with a higher affinity. On the other hand, preimmunization of rabbits with different doses of BGG caused either enhancement or suppression of the hapten-specific antibody response, depending on the priming dose of BGG. The suppressed antibody response was always associated with a marked decrease in the antibody affinity. If rabbits were partially tolerized with a large dose of soluble BGG, some of the animals produced little antibody against hapten (DNP) coupled to this carrier, and the affinity of produced antibody was low. However, other rabbits tolerized with BGG produced large amounts of anti-DNP antibody upon hyperimmunization with DNP-BGG, whose affinity was only slightly lower than that of the control. These results can be harmonized if it is assumed that the thymus plays an important role in the maturation of the immune response. It is postulated that T cells, in numbers ordinarily available, would first assist in the proliferation of antihapten antibody-forming cell precursors already selected by antigen, thus accounting for the rapid increase of antibody affinity in the early stage of immunization. However, after a larger number of carrier-specific T cells are made in response to continued immunization, these would suppress antibody-forming cells. The suppression would be greater for cells with higher affinity for antigen, resulting in a decrease in antibody affinity. This postulate explains preferential stimulation and suppression of cells having higher affinity receptors under circumstances in which T cell are relatively depleted or overstimulated, and further permits an explanation for the decrease of antibody affinity after long-term immunization.

Successful treatment of an infant with severe combined immunodeficiency by transplantation of bone marrow cells from an uncle

A 4½-month-old boy suffering from congenital severe combined immunodeficiency was successfully treated by transplantation of bone marrow-derived cells. His parents were cousins in the first degree. The donor was a 32-year-old maternal uncle, who was HL-A genotypically identical with the patient as was shown by serological typing and MLC. A stem cell rich fraction of the donor's bone marrow was prepared by albumin gradient centrifugation. The infant showed a full immunological reconstitution without any sign of GVH disease. Remarkably the only allotypic marker of his IgG which was different from the donor allotype remained in the serum after transplantation, and even showed an increase of its level.

The infant was nursed in strict reverse isolation and his unfavourable endogenous microflora of high potential pathogenicity was eliminated by antibiotic decontamination.

Bursal origin of bone marrow cells with competence for antibody formation

The impaired antibody response of neonatally bursectomized chickens was restored by bone marrow cells from normal—but not from bursectomized—syngeneic donors. Chimaerism of donor cells in the recipients was demonstrated using the sex chromosomal marker. Attempts to substitute autologous bursal cell suspensions for the bursa in situ were unsuccessful. It is concluded that B lymphocytes in chicken bone marrow have matured in the bursa.

Time-dependent synergism of rats spleen and bone marrow cells

Normal rat spleen cells, when cultured with solubilized sheep erythrocyte stroma in vitro, did not produce antibody but did show an increased rate of thymidine uptake. Normal rat bone marrow cells did not show a similar increase in thymidine uptake when cultured with solubilized stroma. Culture of these two cell types together with antigen resulted in a synergistic increase in thymidine uptake which decreased in intensity as the animals aged. The bone marrow population is responsible for this diminished synergistic activity.

In vitro-initiated secondary anti-hapten response. II. Increasing cell avidity for antigen

Decreasing antigen in vivo may preferentially stimulate cells with the potential for synthesis of high-affinity antibody through activation of surface receptors with similarly high affinity. This selection should result in cells with increased sensitivity to lower antigen concentrations, cells with greater avidity for antigen. We have followed the in vivo changes in anti-TNP memory-cell sensitivity by initiating the secondary anti-hapten response in vitro. This response was determined by anti-TNP plaque assay. The results indicate that cell populations with increased sensitivity for antigen continue to emerge with time after priming and that this sensitivity may increase 1000-fold in a 4 month period. Increased sensitivity to stimulation by antigen is concomitant with suppression by higher, previously stimulatory doses as in high zone immune tolerance. The data support the hypothesis that memory cells of high avidity result from the selective pressure of diminishing in vivo antigen concentration.

Cells involved in cell-mediated and transplantation immunity. II. A consideration of the functional identity of the cells involved in both humoral and cell-mediated immunity: a phylogenetic approach

The literature concerned with the types of cells that participate in the humoral and cell-mediated immune response has been reviewed. It is postulated that the initial cells that are involved in mediating both types of immunity are functionally identical in that both are antigen-reactive cells. In the case of the humoral immune response, the interaction of the antigen-reactive cells with the antigen leads to the release or transfer of "information" to the antibody-forming cell, resulting in the synthesis and secretion of antibody molecules. In the case of cell-mediated immunity, it is considered that the primitive antigen-reactive cell itself transforms into the sensitized cell which infiltrates the site of antigen administration.

Cells involved in cell-mediated and transplantation immunity in the rabbit. I. The noninvolvement of the bone marrow antigen reactive cell in the transplant rejection reaction

Rabbits were subjected to 800 r total body irradiation to render them immunoincopetent with respect to the humoral immune response. These rabbits were, however, only slightly less capable of rejecting skin allografts than nonirradiated rabbits. Furthermore, the administration of normal or specifically "primed" bone marrow cells (bone marrow obtained from a rabbit injected one to two days previously with the spleen cells obtained from the prospective skin donor) did not enhance or inhibit the graft rejection reaction. It is concluded that the cells mediating the humoral immune response are different from those mediating the cellular immune response.

In vitro induction of specific unresponsiveness of immunologically reactive, normal bone marrow cells

Normal rabbit bone marrow cells have been studied according to their immunological reactivity in vitro. The test system involved stimulation by antigen after the subsequent stimulation into cellular proliferation by measuring the uptake of tritium-labeled thymidine. Specific separation of immunological reactivity was obtained by filtration of cells through antigen-coated bead columns. All experimental evidence supported the view that this separation was due to the existence of preformed antibody molecules on the outer cell surface of the antigen-recognizing cells. The response to antigenic stimulation was shown to be strictly dose related and, using supraoptimal concentrations of one antigen, no increased DNA synthesis was recorded. That this state of unresponsiveness represented a state of immunological paralysis was indicated by the normal response of these cells to stimulation by a second antigen in optimal concentration. Thus both methods, cell separation on antigen-coated columns or induction of specific unresponsiveness by antigen in vitro, can produce a cell population specifically devoid of cells reactive against a given antigen.

Cells involved in the immune response. XII. The differing responses of normal rabbit lymphoid cells to phytohemagglutinin, goat anti-rabbit immunoglobulin antiserum and allogeneic and xenogeneic lymphocytes

Cells of the different lymphoid organs in the normal adult rabbit were investigated for their capacity to respond in vitro to a number of stimuli, such as phytohemagglutinin (PHA), anti-rabbit immunoglobulin antiserum (GARIG) and allogeneic and xenogeneic lymphoid cells, and for their capacity to adsorb radioactively-labeled anti-immunoglobulin antiserum. The bone marrow cells responded minimally to PHA, GARIG, and the allogeneic and xenogeneic stimuli. The thymus cells were unable to respond to stimulation with GARIG although they responded to the other stimuli. The cells of the other lymphoid organs tested responded to all the mitogenic agents, to varying degrees. On the basis of the results presented and the findings of other investigators, it is concluded that: 1. The response of the cells to GARIG indicates a potential capacity to mediate humoral immunity and requires the presence of immunoglobulin or immunoglobulin-like recognition sites on the cell surface. 2. The response of the cells to PHA and allogeneic and xenogeneic cells indicates a potential capacity to mediate cellular immunity and does not necessitate the presence of immunoglobulin-recognition sites on the cell surface. 3. The thymus in the normal adult rabbit consists of cells capable of mediating cellular immunity only. 4. The other lymphoid organs appear to possess cells capable of mediating humoral and cellular immunity.

Cells involved in the immune response. 8. The relationship between the loss and reappearance of antigen-reactive cells and immune responsiveness after irradiation of normal adult rabbits

By appropriate irradiation and cell transfer experiments, a direct correlation was observed between the presence of viable and immunologically active antigen-reactive cells and the capacity of the rabbits to respond following immunization. Rabbits given 800 R total body irradiation were unable to elicit a humoral immune response nor did they possess significant numbers of antigen-reactive cells. The ability to respond with humoral antibody formation did not reappear until antigen-reactive cells could be detected. These results strongly indicate that the presence of competent antigen-reactive cells are necessary for the successful induction of the humoral immune response in the rabbit.

Cells involved in the immune response. 13. The nature of the cellular interactions relating antibody formation and immunologic tolerance: a unified hypothesis

The various cells and cell pathways involved in the induction of the primary humoral immune response have been discussed from the point of view of the unitary, as opposed to the multiple, pathway concept. The immunocompetent cells made unresponsive in the immunologically tolerant animal and the cells capable of responding with antibody formation were considered. It is concluded that there exist multiple cellular pathways through which the humoral immune response may be expressed.

Cells involved in the immune response, IX. Depletion from the normal rabbit bone marrow of antigen-reactive cells directed toward human peripheral leukocytes

Normal adult rabbits were injected intravenously with peripheral leukocytes obtained from a normal human volunteer (donor A). The animals were sacrificed 24 hours later, and their bone marrow cells (primed bone marrow) or bone marrow cells obtained from a normal, unimmunized rabbit (normal bone marrow) were injected intravenously into irradiated (800 r) rabbits. The latter were immunized with peripheral leukocytes of donor A. The antisera obtained from the irradiated rabbits given primed bone marrow cells displayed minimal or no cytotoxic activity toward white cells of either donor A or an unrelated donor B. On the other hand, antisera obtained from irradiated rabbits given normal bone marrow cells displayed high titers of cytotoxic activity with respect to donor A cells only. It is concluded that rabbit bone marrow can be depleted of antigen-reactive cells directed toward white cell antigens following injection of the white cells intravenously and that these bone marrow cells are incapable of conferring antibody-forming capacity, in irradiated recipients, directed to this particular species of white cells. The relevance of these findings to the field of transplantation in general is discussed.

Cells involved in the immune response. XI. Identification of the antigen-reactive cell as the tolerant cell in the immunologically tolerant rabbit

Rabbits were made immunologically tolerant to either human serum albumin or bovine gamma globulin by the neonatal administration of antigen. At 10 wk of age, they were challenged with the tolerogenic antigen and found to be non-responsive. However, these tolerant rabbits could respond with humoral antibody formation directed toward the tolerogenic antigen if they were treated with normal, allogeneic bone marrow or bone marrow obtained from a rabbit made tolerant toward a different antigen. They were incapable of responding if they were given bone marrow obtained from a rabbit previously made tolerant to the tolerogenic antigen. Irradiated rabbits were unable to respond if treated with tolerant bone marrow, but could respond well if given normal bone marrow. Since it has previously been demonstrated that the antibody-forming cell, in an irradiated recipient of allogeneic bone marrow, is of recipient and not donor origin, the data presented strongly indicate that the unresponsive cell in the immunologically tolerant rabbit is the antigen-reactive cell.

Cells involved in the immune response. X. The transfer of antibody-forming capacity to irradiated rabbits by antigen-reactive cells isolated from normal allogeneic rabbit bone marrow after passage through antigen-sensitized glass bead columns

The antigen-reactive cells in normal rabbit bone marrow could be isolated from a suspension of marrow cells by passage of the cells through an antigen-sensitized glass bead column. The cells which passed through the column were deficient in antigen-reactive cells directed to the antigen used to sensitize the glass beads, whereas the cells eluted from the column could transfer antibody-forming capacity to irradiated recipients only with respect to the specific sensitizing antigen. Separation of the bone marrow antigen-reactive cells could not be achieved by passage of the cells through nonsensitized glass bead columns or in the presence of excess free antigen in the column. Cells which were retained by, and later eluted from, the antigen-sensitized glass bead columns were mostly small mononuclear cells, whereas cells which passed through the columns were morphologically similar to the original unfractionated bone marrow cell suspension. The data indicate the presence of an antibody or antibody-like structure, with defined immunological specificity, on the surface of the normal bone marrow antigen-reactive cell.