SURFACE ANTIGENS OF IMMUNOCOMPETENT CELLS : III. IN VITRO STUDIES OF THE ROLE OF B AND T CELLS IN IMMUNOLOGICAL MEMORY

The effect of preincubation with anti-θ or anti-mouse immunoglobulin (Ig) and complement (C') on immune responsiveness of spleen cells from BALB/c mice immunized with sheep erythrocytes (SE) was investigated. Both treatments greatly depressed the remaining ability to produce a secondary response to SE in vitro. Normal BALB/c spleen cells were far less effective in reconstituting the responses of such depleted cell populations than were much smaller numbers of untreated immune spleen cells. Thymus-derived cell (T cell) memory appeared early after immunization and showed specificity for the immunizing antigens. Recombination of anti-Ig-treated with anti-θ-treated immune spleen cells resulted in virtually complete reconstitution of responsiveness. The presence of immunological memory in T cells and the nature of their surface receptors are discussed.     

GENETIC CONTROL OF IMMUNE RESPONSES IN VITRO : V. STIMULATION OF SUPPRESSOR T CELLS IN NONRESPONDER MICE BY THE TERPOLYMERL-GLUTAMIC ACID60-L-ALANINE30-L-TYROSINE10 (GAT)

In recent studies we have found that GAT not only fails to elicit a GAT-specific response in nonresponder mice but also specifically decreases the ability of nonresponder mice to develop a GAT-specific PFC response to a subsequent challenge with GAT bound to the immunogenic carrier, MBSA. Studies presented in this paper demonstrate that B cells from nonresponder, DBA/1 mice rendered unresponsive by GAT in vivo can respond in vitro to GAT-MBSA if exogenous, carrier-primed T cells are added to the cultures. The unresponsiveness was shown to be the result of impaired carrier-specific helper T-cell function in the spleen cells of GAT-primed mice. Spleen cells from GAT-primed mice specifically suppressed the GAT-specific PFC response of spleen cells from normal DBA/1 mice incubated with GAT-MBSA. This suppression was prevented by pretreatment of GAT-primed spleen cells with anti-θ serum plus C or X irradiation. Identification of the suppressor cells as T cells was confirmed by the demonstration that suppressor cells were confined to the fraction of the column-purified lymphocytes which contained θ-positive cells and a few non-Ig-bearing cells. The significance of these data to our understanding of Ir-gene regulation of the immune response is discussed.     

CELL-TO-CELL INTERACTION IN THE IMMUNE RESPONSE : X. T-CELL-DEPENDENT SUPPRESSION IN TOLERANT MICE

Specific immunological tolerance was induced in CBA mice by a single injection of deaggregated fowl immunoglobulin G (FγG). The unresponsive state was stable on adoptive transfer and irreversible by pretreatment of tolerant cells with trypsin. Tolerant spleen cells could suppress the response of normal syngeneic recipients. They also suppressed the adoptive primary response of spleen cells to FγG in irradiated hosts. The inhibitory effect was on the indirect (7S) plaque-forming cell (PFC) response. Incubation of the tolerant cell population with anti-θ serum and complement reversed the suppressor effect. Furthermore, the addition of purified T cells from normal donors restored the capacity of the anti-θ serum-treated tolerant cells to transfer an adoptive response to FγG. The existence of FγG-reactive B cells was supported by the demonstration of normal numbers of antigen-binding cells in the spleen and thoracic duct lymph from tolerant animals. Moreover, the formation of caps by these cells implied that they could bind antigen normally. These experiments provided direct evidence for the existence of suppressor T cells in the tolerant population. Further evidence was derived from examination of the effect of antigen "suicide". Tolerant spleen cells were treated with radioactive FγG under conditions known to abrogate T-cell helper function. When these cells were transferred together with normal spleen cells into irradiated hosts, suppression of the primary adoptive response to FγG was no longer observed. Inhibition of an adoptive secondary response to FγG was obtained by transferring tolerant spleen cells with primed B cells provided high doses of tolerant cells were used. By contrast low doses exerted a helper rather than a suppressor effect in this system.     

CELL-MEDIATED IMMUNE RESPONSES IN VITRO : I. SUPPRESSION OF THE GENERATION OF CYTOTOXIC LYMPHOCYTES BY CONCANAVALIN A AND CONCANAVALIN A-ACTIVATED SPLEEN CELLS

The effects of soluble concanavalin A (Con A) or Con A-activated spleen cells on the generation of cytotoxic lymphocytes (CL) in mixed leukocyte cultures (MLC) were examined. Mitogenic concentrations of soluble Con A or small numbers of Con A-activated spleen cells substantially inhibited CL responses. The suppression was partial rather than absolute and was critically dependent upon the concentration and time of addition of soluble Con A or Con A-activated spleen cells to the MLC. Suppressive effects of Con-A activated spleen cells were mediated by T cells since suppressor cell activity was abrogated by treatment of spleen cells with anti-θ serum and complement before or after Con A activation. X irradiation of spleen cells before Con A treatment also abrogated generation of suppressor cell activity. After activation by Con A, however, the function of suppressor cells was radioresistant. Although the precise mechanism(s) of suppression is, as yet, unknown, the precursors of CL must be exposed to Con A-activated cells during the early phases of the immune response for suppression to occur. Kinetic studies revealed that suppression of CL responses was not due to a failure to initiate an immune response, but represented a response which developed initially, but subsequently aborted. The relevance of these observations to the concepts of T-cell-T-cell interaction and regulatory control of immune responses by T cells is discussed.     

IMMUNOLOGICAL MEMORY IN MICE : II. CELL INTERACTIONS IN THE SECONDARY IMMUNE RESPONSE STUDIED BY MEANS OF IMMUNOGLOBULIN ALLOTYPE MARKERS

Congenic mice, differing genetically only at the loci coding for immunoglobulin H chain (or Fc) structures, have been used to study cell interactions in the 7S (γG_2a) antibody response to sheep erythrocytes (SRBC), as detected by the Jerne plaque-forming cell (PFC) method. The interaction between thymus and bone marrow cells was studied in adult thymectomized irradiated recipients, protected with syngeneic bone marrow and injected with thymus cells from the partner congenic strain. All of the γG_2a PFC detected in the spleens of these mice were of bone marrow allotype. Adoptive secondary immune responses were then studied to determine whether a similar interaction between memory cells and bone marrow derived cells could be detected. Primed spleen cells from the partner congenic strain, or a subpopulation of these cells obtained by BSA density gradient fractionation, were injected into irradiated recipients alone, or together with syngeneic nonimmune spleen or bone marrow cells. All γG_2a PFC detected in these experiments were of primed cell allotype. There was no evidence that antibody forming cell precursors in normal spleen or bone marrow participate in the adoptive secondary immune response detected 7 days after transfer of primed spleen cells. This was true regardless of whether the bone marrow cells were injected at the time of transfer, or were injected 1–2 wk earlier and allowed to become established in the spleens of recipient mice. Although no specific cell interaction was seen, bone marrow (and, to a lesser degree, normal spleen) cells were found to have a nonspecific enhancing effect on the adoptive secondary response when they were injected together with the primed spleen cells. This enhancement was not evident if the bone marrow cells were injected 1 or 2 wk prior to primed cell transfer.     

MATURATION OF THE HUMORAL IMMUNE RESPONSE IN MICE

In spite of the prenatal appearance of immunoglobulin-bearing lymphocytes and θ-positive lymphocytes in the spleens of Swiss-L mice, these mice are not able to produce detectable levels of humoral antibodies in response to antigen until after 1 wk of age. Adult levels of response are not achieved until 4–8 wk of age. In the presence of bacterial lipopolysaccharides, which can substitute for or enhance T-cell function, the B cells from young Swiss-L mice were found to be indistinguishable in function from adult B cells, both with respect to the numbers of plaque-forming cells (PFC) produced in vitro in response to antigen and with respect to the kinetics of PFC induction. The spleen cells from young Swiss-L mice are significantly less sensitive than adult spleen cells, however, to stimulation by the T cell mitogens, concanavalin A (Con A) and phytohemagglutinin (PHA). Very few Con A-responsive cells could be detected at birth but the numbers increased sharply with age until 3 wk after birth. On the other hand, PHA-responsive cells could not be detected in the spleen until about 3 wk of age. The latter cells were found to respond also to Con A, but at a lower dose (1 µg/ml) than that required for the bulk of the Con A-responsive cells (3 µg/ml). The cells that respond both to PHA and to Con A appear in the spleen at about the time that Swiss-L mice acquire the ability to produce humoral antibodies, and these cells can be depleted from the spleen by the in vivo administration of antithymocyte serum. The development of humoral immune responses in these mice therefore appears to be correlated with the appearance of recirculating T lymphocytes that are responsive both to PHA and to Con A.     

Changes in suppressor mechanisms during postnatal development in mice

The activity of suppressor cells from spleens of mice of varying ages was assessed by their addition to cultures of normal or SRBC immune spleen cells together with a challenge of SRBC. 1-wk and adult spleen cells were highly suppressive of the secondary in vitro antibody response to SRBC. 3-wk spleen cells were less active in suppressing this response. The nature of the suppression and the character of the suppressor cells changed in this period. Whereas adult spleen cells demonstrated specificity, 1-wk cells nonspecifically suppressed all responses tested. Further, unlike adult suppressor cells (which are Thy.1.2 positive), 1-wk suppressor cells are insensitive to anti-Thy.1.2 treatment in this system. Both cells are nonadherent to glass beads and nylon wool and are undetectable in the normal thymus.     

CELL-TO-CELL INTERACTION IN THE IMMUNE RESPONSE : VII. REQUIREMENT FOR DIFFERENTIATION OF THYMUS-DERIVED CELLS

Experiments were designed to test the possibility that thymus-derived (T) cells cooperate with nonthymus derived (B) cells in antibody responses by acting as passive carriers of antigen. Thoracic duct lymphocytes (TDL) from fowl γG-tolerant mice were incubated in vitro with fowl anti-mouse lymphocyte globulin (FALG), which was shown not to be immunosuppressive in mice. On transfer into adult thymectomized, irradiated, and marrow protected (TxBM) hosts together with a control antigen, horse RBC, a response to horse RBC but not to fowl γG was obtained. By contrast, TxBM recipients of nontolerant, FALG-coated TDL responded to both antigens and the antibody-forming cells were shown to be derived from the host, not from the injected TDL. These findings suggested that, under the conditions of the experiment, triggering of unprimed B cells in the spleens of TxBM hosts was not achieved with antigen-coated tolerant lymphocytes. Another model utilized the ability of B cells to bind antibody-antigen complexes. Spleen cells from TxBM mice, incubated in vitro with anti-fowl γG-fowl γG·NIP, were injected with or without normal TDL (a source of T cells) into irradiated hosts. Only mice given both cell types could produce an anti-NIP antibody response. In a further experiment, spleen cells from HGG·NIP-primed mice were injected together with NIP-coated B cells (prepared as above) into irradiated hosts. A substantial anti-NIP antibody response occurred. If, however, the T cells in the spleens of HGG·NIP-primed mice were eliminated by treatment with anti-θ serum and complement, the NIP response was abolished. It was concluded that antigen-coated B cells could not substitute for T cells either in the primary or secondary response. Treatment of T cells from unprimed or primed mice with mitomycin C impaired their capacity to collaborate with B cells on transfer into irradiated hosts. Taken together these findings suggest that before collaboration can take place T cells must be activated by antigen to differentiate and in so doing may produce some factor essential for triggering of B cells.     

Interleukins production and responsiveness in Fisher rats with adjuvant-induced disease: role of suppressor cells

Splenic macrophages from AID Fisher rats produce normal levels of IL-1, in contrast to IL-2 which is significantly lower than normal. A state of hyporesponsiveness of spleen cells to Con-A and PHA occurs with similar kinetics to and is correlated with the development of an articular arthritis; IL-1 addition to AID spleen cell cultures does restore to normal their deficient response, in contrast to addition of IL-2 or rIL-2. The spleen cells from normal or AID rats are equally sensitive to the inhibitory effects of suppressor glass adherent cells found in AID spleens on lymphocyte proliferation. Our results indicate that these suppressor cells interfere with IL-1 production or IL-1 binding to T-cells and that this interference is not due to passive absorption of interleukins by these cells.     

Bacterial cell wall-induced immunosuppression. Role of transforming growth factor beta

Group A streptococcal cell wall (SCW)-injected rats exhibit a profound immunosuppression that persists for months after the initial intraperitoneal injection of SCW. The goal of this study was to determine the mechanisms for the suppressed T lymphocyte proliferative responses in this experimental model of chronic inflammation. When spleen cell preparations were depleted of adherent cells, restoration of T cell proliferative responses to Con A and PHA occurred, implicating adherent macrophages in the regulation of immunosuppression. Furthermore, macrophages from SCW-treated animals, when cocultured with normal spleen cells in the presence of Con A or PHA, effectively inhibited the proliferative response. Supernatants from suppressed spleen cell cultures were found to inhibit normal T cell mitogenesis. Taken together, these results implicated a soluble macrophage-derived suppressor factor in the down regulation of T cell proliferation after exposure to SCW in vivo. Subsequent in vitro studies to identify this suppressor molecule(s) revealed the activity to be indistinguishable from the polypeptide transforming growth factor beta (TGF-beta). Furthermore, TGF-beta was identified by immunolocalization within the spleens of SCW-injected animals. The cells within the spleen that stained positively for TGF-beta were phagocytic cells that had ingested, and were presumably activated by, the SCW. These studies document that TGF-beta, previously shown to be a potent immunosuppressive agent in vitro, also effectively inhibits immune function in chronic inflammatory lesions in vivo.     

IMMUNE RESPONSES IN VITRO : V. SUPPRESSION OFγM, γG,ANDγA PLAQUE-FORMING CELL RESPONSES IN CULTURES OF PRIMED MOUSE SPLEEN CELLS BY CLASS-SPECIFIC ANTIBODY TO MOUSE IMMUNOGLOBULINS

Suppression of Ig class-specific PFC responses by class-specific antibody to mouse immunoglobulin was studied in cultures of spleen cells from immunized mice. In contrast to cultures from normal mice where anti-µ suppressed responses in all Ig classes, anti-µ had progressively less suppressive effect on γ₁ and γ₂ responses in cultures from immunized mice with time after immunization. This was most pronounced at 10 days after immunization when anti-µ suppressed γM and γA responses, but had no or slight effect on γ₁ or γ₂ responses which were still suppressed with anti-γ₁ and anti-γ₂. These changes in precursor cell susceptibility to anti-µ were antigen specific.     

IMMUNOLOGICAL MEMORY IN MICE : III. MEMORY TO HETEROLOGOUS ERYTHROCYTES IN BOTH T CELL AND B CELL POPULATIONS AND REQUIREMENT FOR T CELLS IN EXPRESSION OF B CELL MEMORY. EVIDENCE USING IMMUNOGLOBULIN ALLOTYPE AND MOUSE ALLOANTIGEN THETA MARKERS WITH CONGENIC MICE

Using anti-allotype sera and AKR anti θC3H sera, a requirement for two cell types has been demonstrated in the adoptive secondary response of mice to heterologous erythrocytes. The cell types have been designated B cells [precursors of plaque-forming cells (PFC)] and T cells (thymus-influenced cells, not providing precursors of detectable PFC). The in vivo indirect PFC response of spleen cells from primed mice is markedly reduced by in vitro treatment of the cells with a mixture of anti-θ serum and guinea pig serum (Anti θ + GPS). This B cell response is fully restored to control levels by thymus cells from normal mice which do not themselves provide precursors of indirect PFC. Thus memory is carried by the B cell lineage but the expression of this memory is dependent on the presence of a cell population which is sensitive to Anti θ + GPS and which is replaced functionally by unprimed T cells. When assayed for T cell activity, thoracic duct cells from specifically primed mice are better than cells from nonspecifically primed mice in restoring the B cell response of spleen cells from immunized mice. Moreover, the T cell activity of a reconstitutive cell population from primed mice is reduced by incubation with Anti θ + GPS. We conclude that memory to heterologous erythrocyte antigens is carried by the T cell lineage as well as the B cell lineage even though unprimed T cells are sufficient for expression of B cell memory.     

ACTIVE SUPPRESSION AS A POSSIBLE MECHANISM OF TOLERANCE IN TETRAPARENTAL MICE

Previous work has indicated that tetraparental mice, chimeric since the eight-cell stage because of embryo fusion using histoincompatible strain combinations, possess autospecific immune cells and blocking antibodies. Although this phenomenon has been demonstrated in vitro, it may have relevance to the self-tolerance shown by these mice in vivo. The experiments described here indicate that spleen cells from tetraparental mice can block mixed lymphocyte reactions between the two parental cell types, but not between unrelated strains. Furthermore, this suppressive ability is not affected by an otherwise effective treatment of the tetraparental spleen cells with anti-θ antibody and complement. The in vitro experimental system elaborated here should help to characterize the cell type responsible for the suppression.     

Enhancement of NK-cell activity in normal and tumor-bearing mice after administration of aclacinomycin

Aclacinomycin (ACM) a new cytotoxic antibiotic employed in cancer chemotherapy, can either enhance or inhibit the NK-cell activity of the immune system, depending on the dose administered. A single intraperitoneal injection of 2-4 mg/kg of ACM augments the cytolytic activity by spleen and peritoneal exudate cells of normal mice and spleen cells depleted of nylon-adherent cells and peritoneal exudate cells of tumor-bearing mice. In contrast to the stimulatory effect of NK-cell activity by low doses of ACM, a single injection of 8 mg/kg of this agent leads to depression in the level of NK-cell activity in both normal and tumor-bearing animals. We suggest that the mechanism through which the ACM enhances NK-cell activity may be through the deletion of a suppressor cell population acting on the NK cells.     

SURFACE ANTIGENS OF IMMUNOCOMPETENT CELLS : I. EFFECT OF ϑ AND PC.1 ALLOANTISERA ON THE ABILITY OF SPLEEN CELLS TO TRANSFER IMMUNE RESPONSES

Spleen cell transfer studies were done in BALB/c strain mice in an attempt to define the role of θ-antigen-bearing lymphoid cells in immune responses to SE. Incubation with alloantiserum to θ-C3H and rabbit C' virtually completely abolished the ability of the cells to transfer both primary and secondary (IgM and IgG) responses to 650 R irradiated recipients. Normal thymus cells partially reconstituted the ability of such treated cells to transfer the primary but not the secondary response. The results are interpreted as showing immunological memory for SE in the θ-bearing thymus-derived cells. Incubation of the spleen cells with alloantiserum to the PC.1 antigen present on antibody-forming cells did not significantly affect the ability to transfer either primary or secondary response.     

SYNERGY AMONG LYMPHOID CELLS MEDIATING THE GRAFT-VERSUS-HOST RESPONSE : V. DERIVATION BY MIGRATION IN LETHALLY IRRADIATED RECIPIENTS OF TWO INTERACTING SUBPOPULATIONS OF THYMUS-DERIVED CELLS FROM NORMAL SPLEEN

Spleen cells from normal adult mice were injected into lethally irradiated adult syngeneic recipients. 24 h later, cell suspensions were prepared from the recipients' spleens or peripheral lymph nodes and tested either alone or combined for their capacity to elicit graft-versus-host (GVH) reactions in neonatal F₁ recipients, using the Simonsen spleen weight assay. Either the lymph node-seeking subpopulation or the spleen-seeking subpopulation alone was markedly deficient in its ability to provide a GVH reaction when compared with the normal population from which it was derived. However, an appropriate mixture of the two had a reactivity characteristic of the parent population. Both subpopulations were sensitive to treatment with anti-θ antibody and complement in vitro. These results provide a convincing demonstration of the functional heterogeneity within the pool of thymus-derived cells present in a single normal lymphoid tissue. They strongly suggest that the normal expression of GVH reactivity of such a tissue involves an interaction among distinct subpopulations of thymus-derived cells.     

BOUND COMPLEMENT AND IMMUNOLOGIC INJURY OF BLOOD VESSELS

Rats and guinea pigs were depleted of complement (C') by treatment with heat aggregated human γ-globulin (agg HGG), zymosan, anti-β1C globulin, and carrageenan. Although antigen and antibody were bound to vascular structures, Arthus reactions were inhibited. This inhibition was characterized by the lack of C' binding to walls of vessels, the lack of polymorphonuclear (PMN's) cellular infiltrates, and the lack of significant vascular damage. When the same animals were followed for several hours thereafter, levels of serum C' began to rise, C' was bound in tissues, PMN infiltrates appeared, and immunologic vasculitis developed. Blood counts, chemotaxis of PMN's induced by lysates of PMN granules, together with studies on motility and phagocytosis by PMN's obtained from C' depleted rats, failed to establish any abnormality in these cells which would account for inhibition of Arthus reactions. The specificity of C' depletion in terms of effects in the first four reacting components of guinea pig C' was studied. Treatment with agg HGG led to loss of activity in all components, whereas zymosan and anti-β1C globulin predominately affected the third component (C'3c). Carrageenan mainly affected the first two reacting components of C'. Thus, the availability of the 3c component, or a subsequently reacting component, correlated with the attraction of PMN's to immune reactants in vivo. Various antibodies with different C' fixing capacities in vitro were tested for their ability to induce immunologic vasculitis in normal animals. In rats, only those antibodies which fixed C' in vitro possessed biological activity, whereas in guinea pigs, all antibodies tested, regardless of C' fixation in vitro, induced Arthus reactions. For a given antibody in rats the vasculitis-inducing property was reflected in its ability to bind C' in vascular structures. Rats depleted of circulating PMN's by specific antibody were tested for Arthus activity. Although concentrations of immune reactants and C' were readily detected in vascular structures, no PMN infiltration occurred and significant vascular damage was averted.     

Immune response to murine neuroblastoma: effects of in vitro culture of the tumor. Mitogen and mixed lymphocyte culture responses, interleukin-2 production, suppression and natural killer activity

The cellular immune response in A/J mice inoculated with in vitro cultured neuroblastoma (NB) cells is completely different from the response obtained after inoculation of in vivo passaged NB cells. Indeed, inoculation of in vivo grown tumor cells leads to a strongly decreased MLC and PHA response of the host spleen cells. This depressed response is not reversed by in vitro addition of indomethacin, but correlates with a low IL-2 production by the spleen cells. In addition, non-specific suppressor cells are present in the spleen and in the peritoneal cavity. The splenic suppressor cells are of low specific gravity and they are nylon wool adherent. The suppressor capacity is not reduced by anti-Thy plus rabbit complement treatment. Another effect of in vivo maintained NB cells is that the natural killer (NK) activity of the spleen cells of the host is increased 4-5 fold 2 days after inoculation of the tumor cells. On the contrary, in vitro passaged NB cells do not induce a reduced MLC and PHA responsiveness, and the IL-2 production of the host spleen cells remains nearly normal. No non-specific suppression can be demonstrated and the NK activity is not augmented 2 days after inoculation. We can conclude that it is very important in which condition tumor cells are maintained when used to study anti-tumor immunity.     

IMMUNOLOGIC REACTIONS TO HAPTENS ON AUTOLOGOUS CARRIERS : I. PARTICIPATION OF BOTH THYMUS-DERIVED AND BONE MARROW-DERIVED CELLS IN THE SECONDARY IN VITRO RESPONSE

Both thymus-derived (T) and bone marrow-derived (B) lymphocytes participate in the response to a hapten 4-hydroxy-3-iodo-5-nitrophenylacetic acid (NIP), coupled to a nonimmunogenic isologous carrier, mouse gamma globulin (MGG). Spleen cells from mice immunized with NIP-MGG show increased DNA synthesis in vitro when cultured with NIP-MGG. The participation of and requirement for T cells in the response was demonstrated by treating the spleen cells with anti-θ serum. This treatment resulted in a 77% inhibition of the antigen response. Furthermore, adoptively transferred normal thymus cells could be specifically "activated" by NIP-MGG in vivo and they responded secondarily to the antigen in vitro. The active participation of B cells in the secondary response was demonstrated by passing the immune spleen cells through a column coated with polyvalent anti-MGG serum. Column filtration reduced the number of NIP-specific plaque-forming cells and NIP-specific rosette-forming cells (both functions of B cells) and produced a 47% inhibition of the NIP-MGG response. The ability of the cells to respond to phytohemagglutinin (PHA) was not affected by column filtration showing that T cells were not being selectively removed. The participation of B cells in the in vitro NIP-MGG response was also shown by treatment of the spleen cells with antiserum specific for MGG and MGG determinants. B cells were removed by treatment with anti-IgM or polyvalent anti-MGG serum plus complement, resulting in a respective 46 and 49% inhibition of the response to NIP-MGG. (Treatment with anti-IgM serum had no effect on T cells.) The contribution of the hapten NIP to stimulation of T cells was investigated using NIP-MGG-activated thymus cells. These activated T cells responded in vitro very well to the NIP-MGG complex but not to the MGG carrier alone demonstrating the requirement of the hapten for T cell stimulation. The response was also partially inhibited (41%) by incubating the activated cells with NIP coupled to a single amino acid (epsilon-aminocaproic acid) before addition of NIP-MGG. These results demonstrated that T cells recognize the hapten NIP when it is coupled to the isologous carrier MGG.     

CELL-TO-CELL INTERACTION IN THE IMMUNE RESPONSE : VI. CONTRIBUTION OF THYMUS-DERIVED CELLS AND ANTIBODY-FORMING CELL PRECURSORS TO IMMUNOLOGICAL MEMORY

Collaboration between thymus-derived lymphocytes and nonthymus-derived antibody-forming cell precursors occurs in the primary antibody response of mice to heterologous erythrocytes and serum proteins. The purpose of the experiments reported here was to determine whether collaboration took place in an adoptive secondary antibody response. A chimeric population of lymphocytes was produced by reconstituting neonatally thymectomized CBA mice soon after birth with (CBA x C57BL)F₁ thymus lymphocytes. These mice could be effectively primed to fowl immunoglobulin G (FγG) and their thoracic duct lymphocytes adoptively transferred memory responses to irradiated mice. The activity of these cells was impaired markedly by preincubation with CBA anti-C57BL serum and to a lesser extent by anti-θ-serum. Reversal of this deficiency was obtained by adding T cells in the form of thoracic duct cells from normal CBA mice. Cells from FγG-primed mice were at least 10 times as effective as cells from normal mice or from CBA mice primed to horse erythrocytes. These results were considered to support the concept that memory resides in the T cell population and that collaboration between T and B cells is necessary for an optimal secondary antibody response. Poor antibody responses were obtained in irradiated mice given mixtures of thoracic duct cells from primed mice and of B cells from unprimed mice (in the form of spleen or thoracic duct cells from thymectomized donors). In contrast to the situation with T cells, the deficiency in the B cell population could not be reversed by adding B cells from unprimed mice. It was considered that memory resides in B cells as well as in T cells and that priming probably entails a change in the B cell population which is fundamentally different from that produced in the T cell population.