The regulatory influence of activated T cells on B cell responses to antigen

Immunological tolerance in bone marrow-derived lymphocytes. I. Evidence for an intracellular mechanism of inactivation of hapten-specific precursors of antibody-forming cells

Administration of the 2,4-dinitrophenyl (DNP) derivative of the copolymer of D-glutamic acid and D-lysine (D-GL) to inbred mice induces a state of DNP-specific tolerance in such animals irrespective of their immune status at the time of treatment. Taking advantage of the relative ease with which DNP-D-GL can induce tolerance in an animal previously primed with an immunogenic DNP-carrier conjugate, we have established conditions for tolerance induction in an adoptive cell transfer system. Thus, the adoptive secondary anti-DNP antibody response of DNP-keyhole limpet hemocyanin (KLH)-primed spleen cells was completely, or almost completely, abolished by exposure of such cells to DMP-D-GL either in vivo or in vitro. Tolerance induction in vivo occurred irrespective of whether the DNP-primed cells were exposed to DNP-D-GL in the donor animal before adoptive transfer or in recipient mice after transfer. In the latter situation, it was possible to show that tolerance induction in this model occurs very rapidly (1 hr) and with relatively low doses of tolerogen (50 microg). Incubation of DNP-KLH-primed cells with DNP-D-GL in vitro under varying culture conditions also resulted in depression of the adoptive secondary response of such cells, although the kinetics and degree of tolerance induction in this way were slightly different from that obtained by in vivo tolerization. Utilizing the adoptive transfer tolerance system, it was possible to approach certain questions concerning the mechanism of tolerance induction and fate of tolerant bone marrow-derived (B) lymphocytes in the DNP-D-GL model. The possibility that suppression of anti-DNP antibody from the DNP-D-GL reflects blocking of surface receptor molecules on B lymphocytes has been ruled out by several experimental observations. The most conclusive evidence on this point derives from the failure of enzymatic treatment with trypsin to reverse the tolerant state induced by in vitro exposure of primed cells to DNP-D-GL, whereas trypsinization completely restored the immunocompetence of DNP-KLH-primed cells rendered unresponsive by exposure to DNP-ovalbumin in vitro. The present studies also demonstrate that the tolerant state induced by DNP-D-GL represents a predominantly irreversible inactivation of specific B lymphocytes. This conclusion is derived from experiments in which it was found that tolerance was maintained through as many as two serial adoptive transfers performed over a period of time of at least 24 days from the single exposure of such cells to the tolerogen. Moreover, the possibility that maintenance of tolerance through such serial transfers was due to inadvertent transfer of tolerogenic doses of DNP-D-GL was definitively ruled out. It appears, therefore, that DNP-specific tolerance induced by DNP-D-GL is an example of irreversible inhibition of cell reactivity to antigen reflecting yet-to-be-determined events at the intra- and subcellular levels.

Functional maturation of thymic lymphocyte populations in vitro

Mouse thymocytes were cultured for short periods of time either alone or with one of two supporting cell populations, splenic adherent cells or thymic epithelial cells. The thymus-derived (T) cell activity of thymocytes cultured on supporting cell populations increased dramatically during 2 days of culture, as assayed in the mixed lymphocyte interaction (MLI), response to phytomitogens, and helper cell activity in the in vitro antibody response. The level of activity attained was equal to that of spleen and lymph node lymphocytes and greater than that of steroid-resistant thymocytes. The cultured thymocytes had surface antigens characteristic of mature T lymphocytes with regard to theta and H-2. The appearance of functionally active lymphocytes in vitro depended upon cell division. Most of the active cultured cells arose from cells already undergoing maturation, i.e., from cells with reduced theta determinants and increased H-2 determinants. We therefore have generated a population of thymocytes indistinguishable from peripheral T lymphocytes using simple in vitro techniques. The extent to which the production of these active lymphocytes depends upon in vitro differentiation is discussed.

Radioresistance of carrier-specific helper thymus-derived lymphocytes in mice

The effect of x-irradiation on the capacity of carrier-specific mouse T (thymus-derived) lymphocytes to exert a helper function for hapten-specific B (bone marrow-derived) lymphocytes in vivo has been investigated again. Helper function is abolished by exposure of such cells to x-irradiation before, or immediately after, transfer to adoptive hosts. On the other hand, when exposure to x-irradiation occurs under circumstances in which the carrier-primed cells are well-localized in the appropriate lymphoid organs, i.e., either in the carrier-primed animal or 24 hr after adoptive transfer to syngeneic recipients, the capacity of T lymphocytes to serve as specific helper cells is clearly radioresistant. Evidence indicates that x-irradiation results in undefined, and subtle, changes in the migratory capacity of mouse T lymphocytes, but not in abrogation of T-cell helper function.

Hapten-specific tolerance. Preferential depression of the high affinity antibody response

The induction of tolerance in guinea pigs with a 2,4-dinitrophenyl (DNP) derivative of a copolymer of copolymer of D-glutamic acid and D-lysine (D-GL) leads to a preferential depression of the capacity to produce high affinity anti-DNP antibody in response to immunization with DNP-guinea pig albumin. Thus, immunization 2 wk after tolerance induction with 3 mg of DNP-D-GL results in an immune response in which individual plaque-forming cells (PFC) secreting high affinity anti-DNP antibody are absent and in which the affinity of circulating anti-DNP antibody is reduced. A similar, but less marked, suppression is seen when 0.3 mg of DNP-D-GL is used for tolerance induction. If immunization is delayed until 2 months after tolerance induction, then suppression is restricted to the highest avidity PFC group. Our data is consistent with a state of tolerance in the pool of precursors of anti-DNP antibody-secreting cells induced as a result of their interaction with DNP-D-GL in the absence of specific "helper" cells, which appear to be lacking for DNP-D-GL. In such a situation, the affinity of receptors on precursor cells for tolerogen and the concentration of tolerogen appear to be crucial determinants of whether an individual cell will become tolerant.

The allogeneic effect in inbred mice. II. Establishment of the cellular interactions required for enhancement of antibody production by the graft-versus-host reaction

Experimental conditions have been established for the elicitation of an allogeneic effect on the adoptive transfer secondary anti-2,4-dinitrophenyl (DNP) antibody response in mice. Thus, spleen cells from DNP-keyhole limpet hemocyanin (KLH)-primed mice manifest good secondary anti-DNP responses to a challenge with DNP-KLH, but not with DNP-bovine gamma globulin (BGG), after adoptive transfer to irradiated syngeneic recipients. However, a good adoptive transfer secondary anti-DNP response of such cells can be elicited with DNP-BGG when a second transfer of allogeneic lymphoid cells, in appropriate numbers, is carried out 24 hr before secondary challenge. The advantage to this system is that the DNP-primed cell population as well as the population of allogeneic lymphoid cells are accessible to experimental manipulation such that the T lymphocytes of one or the other can be removed. Utilizing this model, we have established that the allogeneic effect on antibody production can operate on a population of primed B lymphocytes which have been depleted of their isologous T lymphocytes by in vitro incubation with anti-theta serum plus complement. The potential cellular interactions involved in the mechanism of this phenomenon are considered and discussed in detail.

The allogeneic effect in inbred mice. I. Experimental conditions for the enhancement of hapten-specific secondary antibody responses by the graft-versus-host reaction

The administration of allogeneic lymphoid cells to 2,4-dinitrophenyl keyhole limpet hemocyanin (DNP-KLH)-primed mice prepares such recipients for markedly enhanced secondary anti-DNP antibody responses to a DNP conjugate of a heterologous carrier. This allogeneic effect phenomenon, reflecting the development of a graft-versus-host (GVH) reaction, was first described in guinea pigs and has been extended in the present studies to inbred mice. The expression of the allogeneic effect in mice is dependent upon critical factors such as the number and route of administration of allogeneic cells, the time interval between cell transfer and secondary challenge, and the strength of histocompatibility differences between the donor and the host. The transient GVH reaction established by the transfer of allogeneic cells obviates the requirement for carrier-specific helper T cells in secondary anti-DNP responses, as evidenced by the ability to elicit such responses with DNP-D-GL, a substance which presumably does not stimulate effective T cell helper function. These studies also demonstrate that primed B cells which are not an integral part of the active GVH reaction fail to produce enhanced levels of antibody.