In vivo requirement for a radiation-resistant cells in the immune response to sheep erythrocytes

Distinct in vivo functions of two macrophage subpopulations as evidenced by studies using macrophage-deficient op/op mouse

The op/op mice totally lack macrophage growth factor colony-stimulating factor (CSF)-1 and thus, by definition are completely depleted of CSF-1-dependent functions of the macrophage cell lineage. Moreover, they possess a severe and generalized macrophage deficiency. However, residual macrophages of these mice should still have normal CSF-1-independent functions. Studies designed to elucidate this issue have revealed that op/op mice are capable of normal in vivo phagocytic function and demonstrate normal humoral and cellular response postimmunization with sheep red blood cells. However, release of monokines such as tumor necrosis factor and granulocyte CSF following administration of endotoxin is severely impaired in op/op mice as compared with littermate controls. These studies suggest that the CSF-1-dependent macrophage population (absent in the op/op mouse) is primarily responsible for regulatory functions of these cells mediated by monokines, while the CSF-1-independent macrophage population (present in the op/op mouse) is primarily responsible for the classical macrophage functions in immunity such as phagocytosis, antigen processing and presentation.

Autostimulatory adherent cells in the spleen of aging mice: characterization in the syngeneic host-versus-graft reaction

Enlargement of the popliteal lymph node (PLN) of 6-week-old mice were elicited by the footpad injection of spleen cells of sex-matched, syngeneic, older mice, but not of 6-week-old mice, in a fashion of host-vs.-graft reaction. Effective stimulating cells in the inoculum seem to be Ia-bearing adherent cells. On the other hand, neither B and T cells nor immunoglobulin-secreting cells were effective for host T cell stimulation. Among nonlymphocytic adherent cells, only those attached to plastic dishes after a 24 h-incubation, enriched in macrophages, showed the stimulatory activity for the young recipients, while cells which had adhered once but detached and became non-adherent during a 24 h-incubation or a crude non-macrophage fraction did not induce the PLN response. Thus, the age-related antigenic change may occur on macrophages but not on dendritic cells. The effective cells should be alive, heat-killed cells being impotent to elicite the response. Such spleen adherent cells of aged mice were found to be also stimulative for age-matched recipients, when they are older than 3 months. Autostimulation by macrophages might be responsible, at least in part, for the age-related change of immune functions.

Ontogeny of T-cell mitogen response in Lewis rats. III. Juvenile adherent suppressor cells block adult mitogen responses

Spleen cells from suckling female Lewis rats (4 to 20 days old) were able to suppress mitogenic responses to concanavalin A (Con A) and phytohemagglutinin (PHA) of spleen or thymus cells from adult female Lewis rats and thymus cells from suckling Lewis rats. Thymus cells from suckling rats were unable to suppress adult spleen cell mitogenic responses to Con A. Removal of carbonyl iron (cFe)-, plastic-, or nylon-wool-adherent cells removed the suppressive action of juvenile spleen cells, but irradiation did not. Separated plastic-adherent spleen cells from suckling animals suppressed adult mitogenic responses to Con A. at optimal Con A doses 2-mercaptoethanol (2-ME, 2 X 10(-5) M) abolished the suppressive effect of juvenile cells, however, at the hyperoptimal dose of Con A (125 micrograms/ml) even higher doses of 2-ME did not relieve suppression by juvenile cells. These suppressor cells in suckling pups were affected by early weaning which decreased suppression, resulting in enhanced mitogenic responses of juvenile cells and removal of the ability to suppress adult mitogenic response.

Ontogeny of T-cell mitogen response in Lewis rats: II. Early appearance and loss of suppressor activity

Spleen cells from rats 2 to 132 days old were cultured with 1-125 micrograms/ml Concanavalin A (Con A). At high doses of Con A, the high spontaneous thymidine uptake of spleen cells from rats 15 to 21 days old was suppressed, whereas spleen cells from younger rats showed no suppression of spontaneous mitogenesis at equally high Con A doses. Removal of either plastic-, nylon wool-, or carbonyl iron (cFe) adherent cells not only removed suppression of background by high Con A doses, but also allowed mitogenic responses at adult levels in normally unresponsive 15 to 21 day old pups. Low doses of X-irradiation did not cause a similar loss of suppression. We suggest that although there is an influx of ConA responsive cells into the rat spleens at 15 to 16 days, the mitogen responses of these cells are suppressed by an adherent cell population which is activated by high doses of Con A.

The role of macrophages in promoting the antibody response mediated by liposome-associated protein antigens

The effect of the in vivo depletion of macrophage function on the plaque-forming cell (PFC) response to liposome-associated bovine serum albumin (LSM-BSA) in mice was investigated. Suppression of macrophage activities was accomplished by the intraperitoneal administration of carrageenan (CGN), a sulphated polygalactose which selectively inhibits macrophage function without interfering with the reactivity of T- and B-lymphocytes. Thus, control animals injected with CGN were found to give a significantly suppressed PFC response to sheep red blood cells, a macrophage-dependent antigen, but not to E. coli lipopolysaccharide, a macrophage-independent antigen. The pretreatment of experimental animals with CGN virtually abolished their antibody response to LSM-BSA in terms of the circulating anti-BSA antibody titers and the BSA-specific PFC response. These results provide evidence to substantiate an obligatory role of macrophages in inducing the humoral response to liposome-associated protein antigens.

Rapid, radiolabeled macrophage culture method for detection of dapsone-resistant Mycobacterium leprae

Mycobacterium leprae cells extracted from the skin biopsies of 14 bacilliferous lepromatous patients were maintained in human-murine macrophage cultures for 3 weeks in the presence of [3H]thymidine and DDS (4,4'-diaminodiphenyl sulfone). All cultures except one containing freshly extracted viable bacilli showed significant incorporation of [3H]thymidine as compared to control cultures containing heat-killed bacilli of the corresponding strain. Six susceptible strains of M. leprae obtained from untreated, freshly diagnosed patients showed significant inhibition of the uptake of the radiolabel in the presence of 3 and 10 ng of DDS per ml per culture. Eight strains of M. leprae obtained from patients clinically suspected of DDS resistance were tested in a similar manner. These strains were also concurrently inoculated in the footpads of mice given orally 10(-2), 10(-3), and 10(-4) g of DDS per 100 g of body weight for 9 months. Concordant results were obtained by both methods: five strains were found to be resistant, one was susceptible, and one was partially resistant. Strain VIII did not incorporate [3H]thymidine in the macrophage cultures and proved to be resistant in the mouse footpad. The macrophage culture system provides a sensitive, rapid screening method for the early diagnosis of DDS resistance.

Accessory cell function in immune responses in vivo: enhancing effect of radioresistant spleen cells on antibody response to SRBC in rats

Spleen cells taken 4 days after lethal irradiation of Lewis rat were used as a source of radioresistant accessory cells. The transfer of 2 x 10(6) cells into syngeneic recipients significantly enhanced the antibody response to an immunogenic dose of SRBC, if given immediately prior to antigen. The enhancing effect was not observed if radioresistant cells were transferred 24 h or later after immunization. Elimination of adherent or phagocytic cells abolished the enhancing capacity of the radioresistant spleen cells. One hour pre-incubation in medium containing 0.4 mg/ml kappa carrageenan potentiated rather than inhibited the enhancing effect of radioresistant spleen cells. IgG PFC response appear to be more sensitive to the effect of the transferred spleen cells as compared with the direct (IgM) PFC response. It is concluded that activated splenic macrophages may enhance antibody response when transferred, at the time of immunization, into an immunocompetent host. Possible mechanisms of action are discussed.

Systemic candidiasis from Candida albicans colonizing the gastrointestinal tract of mice

Reproducible induction of systemic Candida infection was achieved by treating mice in which Candida colonization had been established in the gastrointestional tract by aminobenzylpenicillin treatment. Systemic candidiasis was induced in these mice by X-ray irradiation followed by immunosuppressive doses of dexamethasone or X-ray irradiation followed by immunosuppressive doses of trypan blue. Macrophages seem to play an important role in thie systemic infection.

Studies on the resistance to tolerance induction against human IgG in DDD mice. II. Tolerogen-resistant T-cell population in the spleen

Further studies were carried out to investigate cellular sites of the resistance to the induction of immunological tolerance to HGG in DDD mice, assuming the presence of a subset of tolerogen-resistant splenic T cells. Spleen-seeking T cells were shown to be relatively resistant in comparison with lymph node-seeking T cells. The existence of a tolerogen-resistant T-cell subpopulation was indicated from the experiments demonstrating that tolerance was easily attained after adult thymectomy and that lymph node T cells became much more resistant to tolerance induction after adult splenectomy. The latter experimental result might also exclude the possibility of differences in microenvironment (probably in A cells) between spleen and lymph node. An attempt was made to investigate a possible involvement of A cells in the induction of tolerance. A cells were deprived in vivo by irradiation of the host 3 days prior to spleen cell transfer and in vitro by passing a spleen cell suspension through a Sephadox G-10 column. The deprivation of A cells resulted in priming of the host by the tolerogen rather than easier tolerance induction. No suppressive activity was observed in lymph node cells from tolerized mice. These results suggest that there exists a set of T cells, generated relatively recently in the thymus, preferentially migrating into spleen and there becoming resistant to tolerance induction.

Immune suppression in BALB/c mice bearing the plasmacytoma TEPC-183: evidence for normal lymphocyte but defective macrophage function

This paper analyses impairment of the primary immune response of mice bearing the plasmacytoma TEPC-183. Healthy animals and mice bearing the reported non-immunosuppressive tumour MOPC-104E were used as controls. The defect was shown to affect both primary IgG and IgM responses to chicken cells (CRBC) and to be related to tumour size. However, the primary immune depression could be overcome either by increasing the antigen dose or by using Freund's complete adjuvant together with antigen. Secondary responses were also depressed. This depression was more pronounced if the animals was primed after, rather than before, tumour implantation. Further studies involved the measurement of primary immune responses of immunologically deprived syngeneic mice, after they had been reconstituted with cells from normal or tumour-bearing mice. Lymphocyte reconstitution experiments were carried out in mice which had been irradiated with 950R. Various lymphoid preparations from TEPC-183-bearing mice were unable to bring about such restoration. It is concluded that the impairment of the primary immune response of mice bearing the plasmacytoma TEPC-183 is due to a macrophage, rather than a lymphocyte, abnormality. However, none of these transfer studies suggested that positive suppression of primary immune responses was being mediated by cells from TEPC-183-bearing mice.

Effects of whole-body irradiation on antibody affinity

Mice exposed to a sublethal dose of X-rays were immunized with alum-precipitated DNP-KLH (dinitrophenyl-keyhole limpet haemocyanin) and B. pertussis either before or after irradiation. The primary anti-DNP antibody response was evaluated during 8 weeks after immunization by the equilibrium dialysis technique using ammonium sulphate- precipitated serum globulins and the ligand 3H-labelled xi-DNP-L-Lysine. The serum concentrations of antibody sites in mice immunized 1-5 days before or 2 h-8 weeks after 450 rad were below the values in unirradiated controls at all bleeding times. Antibody affinity, however, was found to be up to 20 fold higher in irradiated mice than in control mice when antigen was injected before, or 3-8 weeks after, irradiation. Spleen cells from mice exposed to 450 rad 1-9 weeks before killing were stimulated in vitro with PHA, ConA, or LPS. Recovery profiles of mitotic responsiveness suggest that enhancement of antibody affinity in irradiated mice could result from relative lack of suppressor T Cells.

Enhanced antibody affinity in sublethally irradiated mice and bone marrow chimeras

Sublethally irradiated mice primed with dinitrophenyl (Dnp)-keyhole limpet hemocyanin immediately after irradiation or 30 days later and subsequently boosted with a second injection of antigen displayed a secondary response to Dnp characterized by antibody affinity greater than that in unirradiated controls. Also, in radiation chimeras primed with Dnp-keyhole limpet hemocyanin 120 days after syngeneic or allogeneic bone marrow transplantation the antibodies against Dnp produced after boosting were of higher affinity than the antibodies raised in normal mice. These findings are tentatively attributed to lack of suppressor thymus-derived lymphocytes (T cells) in sublethally irradiated mice and bone marrow chimeras, in which the enhanced ability to produce antibodies of high affinity may compensate for quantitative defects of the immune system.

Control of the immune response: role of macrophages in regulation of antibody-and cell-mediated immune responses

The ability of peritoneal macrophage subpopulations, separated into different classes according to their size, to reconstitute antibody or cellular immune responses in macrophage-depleted spleen cells has been investigated. Data are presented to show that whether reconstitution is by "normal" or "activated" macrophages, be they syngeneic or allogeneic to the lymphocyte source, different populations reconstitute antibody and cellular immunity. Reconstitution is in general by two classes of macrophages, small and large. The former seem to reconstitute only if syngeneic to the responding lymphocyte pool, whereas large macrophages reconstitute immune responses from allogeneic lymphocytes as well as syngeneic lymphocytes. Evidence is also presented to show that syngeneic large macrophages can determine the type of immune response reconstituted; that is, with greater numbers of large cells only cytotoxic responses (and not T-dependent antibody formation) were reconstituted and vice versa.

Requirement for non-T cells in the generation of cytotoxic T lymphocytes in vitro. I. Use of nude mice as source of non-T cells

The ability of small numbers of LN cells to produce cytotoxic lymphocytes on in vitro culture with allogeneic stimulator cells is greatly augmented by the addition of spleen cells from athymic nude mice. The possibility that the synergism is a result of improved culture conditions or a "feeder effect" is excluded. All cytotoxic cells found in these cultures are shown to be T cells and to arise from precursors contained in the LN-cell component. The nude spleen cell component appears to be providing a required non-T cell which has been lost from the LN component through dilution. Synergism between the two components can occur whether they are syngeneic or allogeneic provided that both can recognize the same alloantigens in the stimulator population.

Enhancing effect of radioresistant spleen cells on the primary immune response against sheep RBC by mouse spleen cells in vitro

Irradiated spleen cells cultured for 3 days, caused a stimulation of the primary in vitro immune response by normal spleen cells. These irradiated spleen cells were fractionated by velocity sedimentation and the fractions were tested for their stimulating activity. Only the macrophage enriched fractions were found to cause stimulation. The macrophages in these fractions were stuffed with erythrocytes and dead cells. The fractions enriched in thymus derived cells, had no effect on the immune response. Irradiated spleen cells cultured for 24 hours caused inhibition. It has not yet been determined whether this inhibition was due to some transient change in the macrophage population during incubation. The stimulating effect by the irradiated spleen cells from SPF mice was strongly reduced, which at least partly could be ascribed to the naturally occurring low number of macrophages in the spleens of these mice.

Requirement for accessory cells in the antibody response to T cell-independent antigens in vitro

The antibody responses of mouse spleen cells in vitro to three thymus-independent (TI) antigens namely, polymeric flagellin (POL) of Salmonella adelaide, DNP-Ficoll and "soluble" sheep erythrocyte (SRBC) antigen, were found to be dependent on adherent accessory cells (A cells) but to a lesser degree than the response to intact SRBC. Evidence for this comes from selective depletion of A cells from spleen cells and reconstitution with A cell-rich populations. Thus, depletion of A cells by adherence on glass resulted in abolition of the response to SRBC leaving the response to POL intact. More thorough removal of A cells by treatment with carbonyl iron powder was required for appreciable reduction of the responses to POL, DNP-Ficoll and "soluble" SRBC. This reduction in responsiveness was not due to poor cell survival after A cell depletion or to the loss of immunocompetent cells since 1) the recoveries of viable cells in all cultures were similar; 2) the contents of theta- and Ig-bearing cells and tritium-labeled POL-binding cells were unaltered after carbonyl iron treatment, and 3) responsiveness was fully restored by the addition of irradiated and anti-theta-treated A cells from the peritoneal cavity or the spleen. Hence, the hitherto A cell independence of TI antigens on which some theories of B cell activation are based is a result of inadequate depletion procedures, and the minimal model for B cell activation must take into account two cell types: B cells and A cells.

Promotion of secondary anti-DNP antibody production in mice by type III pneumococcal polysaccharide (SIII) and dinitrophenylated rabbit antibody to SIII

Type III pneumococcal polysaccharide (SIII) is able markedly to increase the adoptive IgG ANTI-DNP antibody response of B cells primed to DNP-flagellin and stimulated with DNP conjugated to the heterologous carrier, rabbit globulin, provided the latter has anti-SIII activity. The stimulatory effect is apparently accessory cell-dependent as well as being unequivocally T cell-dependent. Although no positive evidence is available, the possibility exists that non-specific T-cell activation is involved in the stimulating effect of anti-SIII plus SIII.

Tolerance induction in TxXBT and TxXB mice

Adult normal mice and those mice which had been thymectomized, X-irradiated, and reconstituted either with bone marrow cells and thymus cells (TxXBT) or with bone marrow cells along (TxXB), were given varying amounts (0.1-5 mg) of deaggregated soluble bovine serum albumin (sBSA). They were challenged 10 days later with an immunogenic form of BSA. TxXB mice were supplemented with normal thymus cells 3 days before the challenge. With any dose of sBSA, TxXBT and normal mice were made tolerant. Only 5 mg of sBSA, the highest dose in these experiments, was effective in inducing the tolerance in TxXB mice. The simultaneous administration of 5 mg of sBSA and 0.1 mg of alumprecipitated BSA plus 0.01 mg of endotoxin resulted in the priming in TxXBT mice but induced tolerance in TxXB mice. These results indicate that: (a) B-cell tolerance could be induced independently of the influence of T cells; (b) the tolerogen susceptibility of B cells may be lower than that of T cells; (c) such a weakly immunogenic agent as the mixture of tolerogen and immunogen could either activate the antibody response in the presence of T cells or induce B-cell tolerance in the absence of T cells.

Role of amino groups in formation of human lymphocyte-xenogeneic erythrocyte rosettes; a proposed mechanism for antigen recognition

Formation of coulombic and possible hydrogen bonds between amino groups on human lymphocytes and negatively charged sites on sheep erythrocytes is involved in rosette formation. Supportive evidence includes rosette inhibition by chemical binding of lymphocyte membrane amino groups, and the results of changing the pH, ionic concentration, and temperature of the reaction. Although the possibility has not been excluded that the amino group dependence of this reaction is related to the property of certain proteins attached to the T-cell (thymus processed) surface, it is suggested that this dependence may be related to a charge pattern recognition in the form of "codes" present on the T-cell membrane. It is speculated that this type of recognition may be a contributory mechanism in the initiation of the T-cell-dependent immune response.

Thymus independence of a collagen-like synthetic polypeptide and of collagen, and the need for thymus and bone marrow-cell cooperation in the immune response to gelatin

Several inbred mouse strains were screened for their ability to respond to the ordered periodic collagen-like polymer (Pro-Gly-Pro)(n), to the random copolymer (Pro(66), Gly(34))(n), to the protein conjugate Pro-Gly-Pro-ovalbumin, to rat tail tendon collagen, rat tail tendon gelatin, and to Ascaris cuticle collagen. Differences were obtained in the magnitude of the antibody titers towards the above immunogens among the strains tested. The level of the response to the ordered polymer (Pro-Gly-Pro)(n) was not similar to that towards the random (Pro(66), Gly(34))(n), confirming differences in the antigenic determinants of the two immunogens. The role of the thymus in the immune response to (Pro-Gly-Pro)(n) and (Pro(66), Gly(34))(n) as well as to two collagens and gelatin, was studied in order to find out a possible correlation with the structural features of the immunogens. Heavily irradiated recipients were injected with syngeneic thymocytes, marrow cells, or a mixture of both cell populations and were immunized with the above-mentioned antigens. An efficient immune response to the ordered collagen-like (Pro-Gly-Pro)(n) was obtained in the absence of transferred thymocytes. The thymus independence of (Pro-Gly-Pro)(n) was confirmed when thymectomized irradiated mice were used as recipients. In contrast with these results, cooperation between thymus and marrow cells was necessary in order to elicit an immune response to (Pro(56), Gly(34))(n). Similarly, the immune response to the triple helical collagen was found to be independent of the thymus, whereas for an effective response to its denatured product, gelatin, thymus cells were required. These findings indicate that a unique three-dimensional structure of immunogens possessing repeating antigenic determinants plays an important role in determining the need for cell to cell interaction in order to elicit an antibody response.

Specific modulation of antibody production in vitro by soluble mediators

The in vitro 19S-PFC response to SRBC reaches a peak at 4 days. After this time, the number of 19S-PFC gradually decreases with a half-life in vitro of approximately 20 hours. The factors which influence this rate of decline of 19S-PFC after 4 days in vitro have been investigated. The decline is not the result of non-specific inhibitors in the tissue medium: medium harvested from cultures at the time of the peak PFC response can support another PFC response by fresh spleen cells. The survival of 19S-PFC in culture is a sensitive function of the number of specific T cells in the culture, since removal of T cells enhances the decline of PFC. Evidence is presented that a θ-negative cell with surface receptors for SRBC can specifically enhance the rate of decay of SRBC-specific 19S-PFC in vitro. This decay is mediated by an antigen-specific soluble mediator which cannot be absorbed by specific antigens. This factor is unlikely to be specific hyperimmune mouse IgG since addition of anti-SRBC IgG at 4 days has no affect on the rate of decay of PFC. Although the properties of the supernatant activity have not been characterized, it might be either an anti-receptor antibody or an antigen—antibody complex.

Specific suppression of immune responses

The models we have discussed in detail demonstrate specific suppression of immune reactivity produced in normal adult animals by antibody and antigen. The mechanism of homeostasis of suppression in these models depends on continued exposure to antigen and on an active response by the host. The active response may include production of antibody directed against specific receptors as well as antibody directed against antigen. Thus, specific regulation of both antibody and cell mediated immunity to an antigen might be achieved by the use of only the biological agents of the response: antigen, antibody, and possibly antibody to receptors. The general implication is that these same biological agents are responsible for autoregulation of immune reactions occurring in nature. Presumably, these agents may be used to suppress or reverse immune responses for appropriate clinical objectives.