The role of adherent cells in B and T lymphocyte activation

Immunosuppressive potential of astemizole against LPS activated T cell proliferation and cytokine secretion in RAW macrophages, zebrafish larvae and mouse splenocytes by modulating MAPK signaling pathway

In this study, the immunomodulatory effects of astemizole (AST) against lipopolysaccharide (LPS) mediated T cell proliferation and induction of inflammation in RAW macrophages (in vitro), and zebrafish larvae (in vivo) were determined. AST significantly suppressed the phagocytic activity of macrophages (3.303 ± 0.115) and inhibited lysosomal enzyme secretion (13.27 ± 2.52) induced by LPS (100 ng/ml). Moreover, AST subdued the morphological deformities such as yolk sac edema (YSE) and spinal curvature curving (SC) by inhibiting ROS generation in zebrafish larvae 24 h after microinjection of LPS (0.5 mg/ml). AST was also shown to inhibit the production of the major cytokines TNF-α (150.8 ± 0.6), IL-1β (276.5 ± 1.6), and PGE₂ (194.6 ± 0.6) pg/ml in RAW macrophages. It also subdued the ROS induced iNOS and COX-2 generated in response to LPS mediated immune dysfunctions in zebrafish larvae. These results suggested the immunosuppression effect of AST. Furthermore, induction of immune-suppression due to AST resulted in significant down-regulation of innate immunity directed by MAPK (p38, ERK and JNK), which was found to be associated with decreased production of acute inflammatory mediators both in vitro and in vivo. To confirm its activity, splenocytes were prepared using BALB/c mice and a mitogen activated splenocyte proliferation assay was also performed. Our findings suggest that AST has the ability to inhibit T cell proliferation and cytokine secretion both in vitro and in vivo by interfering with MAPK signaling pathway. Taken together, our results showed the potential of AST as a countermeasure to immune dysfunction and suggest its use as immunosuppressant compound in inflammatory disease.

Clinical significance of mitogen-induced responses in lymphocytes from patients with chronic lymphocytic leukemia

The mitogenic response patterns as well as surface membrane receptors of peripheral blood lymphocytes were investigated repeatedly during progression of the disease in 27 patients with chronic lymphocytic leukemia. Each patient was characterized by a reproducible mitogenic response pattern. Eleven patients, who required treatment within 0-24 months after diagnosis, had significantly higher cellular responses to dextran sulphate (DxS) and lipopolysaccharide (LPS) than 10 patients who have not required treatment within an observation time of 10-40 months from diagnosis. The high LPS and DxS responses, which may indicate leukemias composed of more immature cells, appear to predict a poor prognosis.

Immunomodulatory effect of methimazole on inbred mice

The effects of antithyroid drug, methimazole (MMI, 1-methyl-2-mercaptoimidazole), on the immune system of inbred mice, C57BL/6, were studied. The proliferative response of splenic lymphocytes to concanavalin A (Con A) and allogeneic stimulator cells was reduced when the mice were provided with 0.1% MMI in tap water ad libitum for two to four weeks. The reduction of proliferative response was correlated with a lower frequency of proliferative spleen cells in the MMI-treated mice. The ability to produce macrophage activating factor of these spleen cells and the levels of hemolytic plaque-forming cells were also reduced. However, the mitogenic response of the splenic lymphocytes to lipopolysaccharide (LPS) was enhanced. In order to investigate whether the impaired cell-mediated and humoral immune systems would increase the susceptibility of the MMI-treated animal to the growth of tumor cells, mice were challenged with a lethal dose of Moloney virus-induced T cell lymphoma of C57BL/6 mice (MBL-2). The time required for 50% of the animals to die was reduced from 15 days for the normal mice to 10 days for the MMI-treated mice.

Prostaglandin and thromboxane in liposomes: suppression of the primary immune response to liposomal antigens

Liposomes containing lipid A as adjuvant and also containing prostaglandin E2 or thromboxane B2 were examined for the ability to influence induction of humoral immunity against liposomal protein or lipid antigens in rabbits. The protein antigen consisted of cholera toxin that was bound to ganglioside GM1 on the surface of the liposomes. High titers of anti-cholera toxin antibodies were produced and IgM and IgG responses were detected. When the immunizing liposomes contained either prostaglandin E2 or thromboxane B2 as part of the lipid bilayer, the primary immune response, involving both IgM and IgG antibodies, was greatly reduced. The secondary immune response observed after a boosting immunization was not suppressed by liposomal eicosanoids. A similar inhibitory effect on the primary response was observed when liposomal lipid antigens were examined instead of cholera toxin. An inhibitory effect of liposomal prostaglandin E2 on the phagocytic uptake of opsonized liposomes by cultured macrophages was also observed, suggesting that liposomal eicosanoids can have direct local effects on macrophages that might influence the immune response to liposomal antigens.

Urtica dioica agglutinin, a new mitogen for murine T lymphocytes: unaltered interleukin-1 production but late interleukin 2-mediated proliferation

Urtica dioica agglutinin, a small-molecular-weight lectin purified from stinging nettle rhizomes, induces murine cell proliferation. U. dioica agglutinin is a specific T-cell mitogen for both thymocytes and spleen T lymphocytes; its mitogenic properties are strictly dependent on the presence of accessory cells. The kinetics of proliferation are markedly different from those of the classical T-cell mitogen concanavalin A, with a 2 to 3-day delay for both splenic and thymic populations and a rate of DNA synthesis twofold lower than that observed with concanavalin A. The late T-lymphocyte proliferation induced by U. dioica agglutinin correlates well with (i) the observed late interleukin-2 production and interleukin-2 receptor expression, and (ii) the long-lasting cyclosporin A-sensitive early activation period. In contrast, the production of interleukin-1 is not different, both in terms of concentration and kinetics, from that observed with concanavalin A.

A preliminary analysis of the effects of elliptinium on immune reactivities in mice

The immune effects of Elliptinium (2-methyl-9-hydroxyellipticinium, 9-HME), a chemical recently shown to possess clinical antineoplastic activity, were investigated in mice. Primary antibody responses to T-dependent and T-independent antigens, DTH reactivity and responsiveness to mitogens were significantly depressed only by post treatment with single drug doses of at least 5 mg/kg i.v., i.e. doses clearly above those known to exert full antitumoral effectiveness and to induce lymphoid cell depletion in the same species. Only drug doses in the LD50 range (i.e. 10 mg/kg) reduced the capacity of NK cells and of activated macrophages to express non-specific cytotoxicity towards tumor target cells. When repeated dose regimens were used, significant immune depression was again seen at doses above those displaying chemotherapeutic activity. Data obtained suggest that at chemotherapeutically effective dosages 9-HME possesses in mice a comparatively low immunodepressive potential and that immune cells mediating natural host defence mechanisms appear especially resistant to this drug.

Mitogenic effects of beryllium and zirconium salts on mouse splenocytes in vitro

The beryllium (Be) and zirconium (Zr) salts, BeSO4 and Zr(SO4)2, each exerted a concentration-dependent stimulation of mouse spleen cell proliferation as measured by an increase in [3H]thymidine incorporation into lymphocyte DNA, although the maximal response induced by Zr(SO4)4 (4-5 fold at 100-200 microM) was greater than that by BeSO4 (2-3 fold at 1-5 microM). Preincubation of splenocytes with low concentrations of BeSO4 (less than 1 microM) or a broad range of Zr(SO4)2 concentrations (2-100 microM) was also found to assist subsequent lectin (concanavalin A; ConA)-mediated lymphocyte proliferation. The results indicate that at defined concentrations Be and Zr salts can both act as lymphocyte mitogens and augment the functional responsiveness of immune cells, which may help explain the characteristic induction of delayed hypersensitivity and production of immunological granulomas by these metals in vivo.

Effect of monoclonal antibodies (MoAb) to class I and class II HLA antigens on lectin- and MoAb OKT3-induced lymphocyte proliferation

We have examined the effect of several monoclonal antibodies (MoAb) to monomorphic determinants of class II HLA antigens, and MoAb to monomorphic determinants of class I HLA antigens and to beta-2-microglobulin (beta 2-mu) on lectin- and MoAb OKT3-induced proliferation of human peripheral blood mononuclear cells (PBMNC) and cultured T cells (CTC). Some, but not all, anti-class II HLA MoAb inhibited the proliferative response of PBMNC to MoAb OKT3 and pokeweed mitogen (PWM). The degree of inhibitory effect varied considerably. This effect was not limited to anti-class II HLA MoAb since anti-class I HLA MoAb and anti-beta 2-mu MoAb also inhibited MoAb OKT3- or PWM-induced proliferative responses. In contrast, the response of PBMNC to phytohemagglutinin (PHA) and concanavalin A (Con A) was not blocked by any anti-class II HLA MoAb. However, some anti-class II HLA MoAb also inhibited the proliferative response of CTC plus allogeneic peripheral blood adherent accessory cells (AC) to PHA or Con A as well as to MoAb OKT3 or PWM. This may be attributable to the substantially greater class II HLA antigen expression by CTC than by fresh lymphocytes. Pretreatment of either CTC or AC with anti-class II HLA MoAb inhibited OKT3-induced proliferation. In contrast, pretreatment of CTC, but not AC, with anti-class I HLA MoAb inhibited the proliferative response of CTC to OKT3. Pretreatment of CTC with anti-class I HLA MoAb inhibited PHA-, Con A and PWM-induced proliferation, to a greater degree than the anti-class II HLA MoAb. It appears as if lymphocyte activation by different mitogens exhibits variable requirements for the presence of cells expressing major histocompatibility determinants. Binding of Ab to membrane markers may interfere with lymphocyte-AC cooperation, perhaps by inhibiting binding of mitogens to their receptors or by interfering with lymphocyte and AC function. We also have examined the role of class II HLA antigens on CTC by depleting class II HLA-positive cells. As expected, elimination of class II HLA-positive AC with anti-class II HLA MoAb plus complement caused a decrease in proliferation of CTC in response to all the mitogens tested. In contrast, elimination of class II HLA-positive CTC was shown to clearly increase proliferation of CTC, perhaps because this may deplete class II HLA-positive suppressor cells.

Monocyte suppressor function in burns: T cell-monocyte interaction in mediating suppression

Reduced in vitro T cell mitogen-induced transformation, low proportion of T cells and increased proportion of non-T cells were found in blood mononuclear cells of patients with severe burns 3-12 days after the injury. High spontaneous proliferation of non-T cells was observed and could be related mainly to the B cell fraction. Monocytes mediated suppression of mitogen-stimulated T cell proliferation. We further studied the role of monocytes in the enhanced suppressor activity of Con A-activated T cells and found that in this assay system, the patient's T cells mediated suppression in collaboration with monocytes. In vitro, increased suppressor function was probably the result of in vivo stimulation of inhibitory activity ascribed to both monocytes and T cells of patients. Addition of indomethacin to cell cultures markedly reduced suppression of lymphocyte proliferation. Less significant reduction was noted when the patient's T cells were activated in vitro by Con A. Adjuvant treatment of burn patients with indomethacin may play a role in alleviating suppression of immune response in these patients.

The immunological activity of plant toxins used in the preparation of immunotoxins--II. The immunodepressive activity of gelonin

The immunological activity of Gelonin, a 30,000 dalton plant protein possessing close similarity to Ricin chain A as a protein synthesis inhibitor which may be of interest for the preparation of antibody-toxin conjugates, was studied in mice. At in vitro concentrations not affecting baseline radioactivity uptake, this substance reduced mitogen responses with the following order of sensitivity PHA less than ConA less than LPS. In microgram/ml concentrations it also markedly reduced macrophage-dependent cytotoxicity while not affecting NK activity. Macrophagic (but not NK) cytotoxicity and mitogen responses were similarly depressed after in vivo treatment. When given before (but not after) stimulus, Gelonin also reduced the primary responses to a T-dependent and, although to a lower degree, to a T-independent antigen, and decreased resistance to allogeneic tumor grafts and L. monocytogenes challenges. The immunopharmacological activity of this and similar substances should be considered in the design of antibody-toxin conjugates and in the evaluation of their therapeutic activity.

Stimulatory and cytotoxic effects of beryllium on proliferation of mouse spleen lymphocytes in vitro

Low concentrations (1-5 microM) of beryllium (Be) salts were weakly mitogenic to mouse spleen cells in vitro as measured by an hydroxyurea-sensitive 2-3fold increase in pulse labelled [3H]-thymidine incorporation into lymphocyte DNA. It is proposed the activation may be induced by a direct interaction of Be2+ with the lymphocyte membranes. Higher concentrations of Be2+ (5-20 microM) produced a gradual loss of the stimulatory response, possibly as the result of either a limited cytotoxic effect or by the established property of intracellularly-accumulated Be2+ to inhibit cell division. In contrast, Concanavalin A-stimulated lymphocyte mitogenesis was markedly decreased by a 20-h preincubation of splenocytes with micromolar concentrations of Be2+, whereas similar pretreatment with lower concentrations (0.1 microM) actually enchanced the subsequent proliferative response. In both cases, supplementary addition of 0.1-1% peritoneal macrophages increased the level of Concanavalin A stimulation. It is concluded, therefore, that inhibition of the proliferative response to accessory cell-dependent mitogens may result from dose-dependent destruction by Be2+ of the macrophage/adherent cell population.

Rat bone marrow precursors develop into dendritic accessory cells under the influence of a conditioned medium

Primary in vitro immune responses require the interaction between T lymphocytes and Ia-positive antigen-presenting cells. Recently, techniques were established including discontinuous bovine serum albumin gradients, adherence, irradiation, and Fc-rosetting which led to a positive selection of rat dendritic cells and their identification as the major if not the only accessory cell for rat T lymphocytes treated with the mitogen, sodium periodate, or stimulator cells in mixed lymphocyte reactions. Rat dendritic cells which were found to be present in both lymphoid and non-lymphoid tissues have a low density, are non-adherent, radioresistant, non-specific esterase-negative, Fc-receptor negative and Ia-positive. Dendritic accessory cells were detected in cultures of low-density bone marrow cells and developed from radiosensitive precursors especially in a medium containing 10-20% of a supernatant elaborated by mitogen-preactivated syngeneic spleen cells. When compared to purified lymph node dendritic cells they were found to be identical in potency and phenotype. Adherent cells from bone marrow possessed neither accessory activity nor influenced the development of dendritic accessory cells. The mature dendritic accessory cells which could be enriched 1000-fold were no longer radiosensitive. The production of dendritic accessory cells from bone marrow precursors was influenced by the culture medium. Serum components were found to suppress their development. However, semipurified factor(s) released by mitogen-preactivated spleen cells enhanced the number of dendritic cells considerably. Activity resided in substances with a molecular weight in the range of 40,000 Daltons. This material could be separated on a Sephadex G 75 column from rat Interleukin 2 which had no effect on the formation of dendritic cells but did support proliferation of accessory cell-depleted, mitogen-treated lymph node cells.

Polysaccharides with sulfate groups are human T cell mitogens and murine polyclonal B cell activators (PBAs) II. Cellulose sulfate and dextran sulfate with two different lower molecular weights

In our previous paper, we reported that various types of carrageenan, dextran sulfate and fucoidan, which are sulfated homopolysaccharides with high molecular weights, were human T cell mitogens and murine polyclonal B cell activators (PBAs) and that heparin, a sulfated heteropolysaccharide, was a very weak human mitogen and mouse PBA. Here we used cellulose sulfate (Mr 7-9 X 10(3], dextran sulfate with two different low molecular weights (Mr 5 X 10(3) and 8 X 10(3], two different condroitin sulfates (Mr 3.5 X 10(4], polyvinyl sulfate and polygalacturonic acid to investigate mitogenic activities of polysaccharides in detail. The following results were obtained. Low-molecular-weight sulfated homopolysaccharides, dextran sulfate and cellulose sulfate, were very weak or not human T cell mitogens. However, they were better murine PBAs. Sulfated heteropolysaccharides, chondroitin 4-sulfate and chondroitin 6-sulfate, hardly induced mitogenic changes in human T cells and mouse B cells, even though the molecular weight of these substances was more than 1 X 10(4). There were no other polymers examined so far which activated both human T cells and murine B cells. The relationship among molecular size, sulfate groups and lymphocyte activation is discussed in detail.

Metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol in alveolar macrophages from rat lung

5 alpha-Reduction of testosterone was observed in lung cells obtained by bronchoalveolar lavage (greater than 95% macrophages) from the rats. This activity was inhibited by progesterone and corticosterone. Production of 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol from testosterone was higher in rat pulmonary alveolar macrophages than by the 800 g supernatant fraction of whole lung homogenate from the same animals. Alveolar macrophages from rats treated with the 5 alpha-reductase inhibitor 17 beta-N,N-diethylcarbamoyl-4-aza-4-methyl-5 alpha-androstane-3-one (5 mg/100 g b.w., s.c.) showed decreased metabolism of testosterone to 17 beta-hydroxy-5 alpha-androstane-3-one and 5 alpha-androstane-3 alpha, 17 beta-diol 4 h after treatment. This metabolism was also decreased in alveolar macrophages from rats exposed to potassium dichromate by intratracheal instillation. When bovine alveolar macrophages were incubated with potassium dichromate, 5 alpha-reduction of testosterone decreased significantly. The function of steroid 5 alpha-reduction in alveolar macrophages is currently not known.

Astrocytes present myelin basic protein to encephalitogenic T-cell lines

Astrocyte proliferation and perivascular lymphocyte infiltration are conspicuous among the cellular changes in the active brain lesions of multiple sclerosis patients. Recent observations have indicated that most of the perivascular lymphocytes are T cells which may be actively involved in the generation of the brain lesions. Much less is known about the significance of the proliferative astrocytes, although the fact that they produce an interleukin-1 (IL-1)-like factor that enhances the release of interleukin-2 by T lymphocytes, may provide a clue. We show here that rat astrocytes are able to present antigen to T lymphocytes in a specific manner which is restricted by the major histocompatibility complex (MHC) and that they can in particular activate myelin basic protein (BP)-specific, encephalitogenic T-cell lines. Only on such interaction do astrocytes express Ia antigens in easily detectable amounts. Antigen presentation by astrocytes may have a central role in the generation of immune responses in the brain.

Role of monocytes in polyclonal immunoglobulin production stimulated by sonicates of periodontally associated bacteria

These studies were initiated to investigate monocyte regulation of polyclonal antibody responses of human peripheral blood lymphocytes stimulated by sonicates of periodontally associated bacteria. With pokeweed mitogen (PWM) as a positive reference, the role of monocytes in the peripheral blood lymphocyte response to Streptococcus sanguis and Wolinella HVS was examined by manipulating the number of monocytes and lymphocytes in culture. In comparison to PWM, optimal responses to the bacterial sonicates required very few monocytes (0.3% of the total cultured cells). Restoration of monocytes to physiological levels resulted in suppression of the response. PWM-stimulated responses were optimal at 5 to 15% monocyte content and were abolished after monocyte depletion. Individuals who were low responders or nonresponders to bacterial sonicates responded at normal levels after manipulation of monocyte concentration. Nonresponders produced normal levels of antibody when the monocyte concentration was reduced to 0.3% but were inhibited after monocyte reconstitution. The effects of monocyte concentration were tested over a wide dose range of bacterial sonicate and found to conform to the observed pattern throughout the dose range tested (10 to 1,000 micrograms/ml). The contrasting monocyte requirement of peripheral blood lymphocytes stimulated with PWM versus bacterial sonicates may reflect a quantitative difference in optimal macrophage concentration or may be due to a qualitative difference in lymphocyte-monocyte interactions in response to these activators.

The effect of removal of adherent cells in lectin and allogeneic cell stimulation of bovine lymphocytes

Macrophages have been shown to play an important role in lymphocyte activation in many species but not unequivocally for bovine. In this study we have shown that when sufficient care is taken to remove macrophages by adherence or by anti-macrophage serum and complement, bovine lymphocytes respond poorly to lectins or to allogenic cells in mixed lymphocyte culture. Addition of macrophages to approximately the same level as found in the unseparated cells restores the proliferative responses. The degree of response shown by the macrophage depleted cultures depends on the lectin concentration. Stimulation with lower doses of lectin is more sensitive to macrophage concentration. The mixed lymphocyte response and the response to Concanavalin A (ConA) are more sensitive to macrophages than is the response to phytohemagglutinin (PHA).

Activation of human T lymphocytes I. Requirements for mitogen-induced proliferation of antigen-specific T lymphocyte clones

In a model system for accessory cell (AC)-dependent mitogen-induced T cell proliferation the response of several human antigen-specific HLA-restricted helper T lymphocyte clones (HTLC) to mitogens was studied. It was found that the HTLC themselves did not or only weakly respond to various mitogens or to oxidation by galactose oxidase, but that the response could be strongly increased if certain tumor cell lines were added to the assay as AC. Pretreatment with lectins or oxidation of either HTLC or AC was effective in stimulating the proliferation of the T cells in this system. Reduction of the aldehydes formed during oxidation completely abolished the stimulatory activity of oxidized B lymphoblastoid cell line. This shows that cross-linking of T cell and AC is required to induce proliferation. When several established cell lines were tested for their capacity to function as AC in this system, profound differences in AC activity were detected. The inability of cells with poor AC activity to stimulate the HTLC was not due to trivial reasons, such as requirements for different mitogen concentrations, a decreased binding of mitogens or suppressive effects. Furthermore, AC activity was not dependent on the presence of Ia antigens on the AC. These findings are discussed with regard to the mechanism of mitogen-induced T cell activation.

The mononuclear phagocyte system of the mouse defined by immunohistochemical localization of antigen F4/80. Relationship between macrophages, Langerhans cells, reticular cells, and dendritic cells in lymphoid and hematopoietic organs

The macrophage-specific antigen F4/80 has been localized in mouse lymphoid and hematopoietic tissue and skin using immunoperoxidase staining. The antigen permits identification of early mononuclear phagocyte precursors in the bone marrow, and is present also on larger cells forming the center of hematopoietic islands and lining vascular sinuses. In thymus F4/80+ cells are numerous in both cortex and medulla and are particularly concentrated around the corticomedullary region. In spleen, lymph node, and gut-associated lymphoid areas the major F4/80+ populations are in the red pulp, the medulla and subcapsular sinus, and the adjacent lamina propria, respectively. F4/80+ cells are rarely seen in T-dependent areas of lymph nodes, spleen, or Peyer's patch, but are present in large numbers in these areas during bacillus Calmette-Guerin (BCG)-induced inflammation. Macrophage infiltration occurs also in lymph nodes from athymic nu/nu mice and is therefore T cell independent. The interdigitating cell of T-dependent areas is F4/80-, but the Langerhans cell of the epidermis of the skin, which bears some ultrastructural resemblance to the interdigitating cell, is F4/80+. We conclude that the two cell types are probably not related.

The degree of monocyte participation in human B- and T-cell activation by phorbol myristate acetate

The DNA synthetic responses of mononuclear cells (MNC), highly purified B and T lymphocytes, and T-cell subsets--OKT4+ and OKT8+ cells--and immunoglobulin production by a tumor-promoting agent, phorbol myristate acetate (PMA), were investigated. The following results were obtained: (1) PMA induced a significant DNA synthesis in MNC, pure B cells, pure T cells, and OKT4+ and OKT8+ cells. (2) Addition of monocytes to B cells did not increase the mitogenic responses more significantly than that of pure B cells alone. (3) PMA induced DNA synthesis in purified T cells significantly, but the addition of monocytes to the T cells augmented the responses markedly. (4) PMA induced polyclonal IgM production but the level of IgM synthesis was lower than that induced by PWM (about 45% at Day 6 culture). (5) Cyclosporin A (CyA) inhibited DNA synthesis induced by Con A and PHA, but did not inhibit the PMA-induced DNA synthesis. It was concluded that although there is a possibility that monocytes are not depleted completely, PMA did not seem to require monocytes for B-cell activation, whereas the level of T-cell activation was potentiated by monocyte addition and PMA probably activated T cells via receptors that are different from those used by Con A and PHA or probably activated T cells without HLA-DR antigen receptors.

Carrageenans, highly sulfated polysaccharides and macrophage-toxic agents: newly found human T lymphocyte mitogens

We obtained the following results, using carrageenans (CGNs) of three types (kappa, lambda and iota), macrophage-toxic agents. 1. CGNs were toxic to human monocytes, cytotoxicity varying from 40% to 60%, as judged by trypan blue dye exclusion test. 2. CGNs were proved to be newly found mitogens for human T cells, whereas CGNs are polyclonal B-cell activators in mice and induced DNA synthesis that peaked at days 6 or 7. In addition, iota CGN induced an early peak of 3H-thymidine uptake at day 1, which found out to be cytoplasmic uptake of 3H-thymidine. 3. Only lambda and iota CGN induced slightly higher DNA synthesis in purified B cells, but both failed to induce polyclonal antibody synthesis in B cells. 4. In spite of the fact the CGNs are macrophage-toxic agents, CGNs could induce Il-1 production by the surviving monocytes. Thus CGN-induced human T-cell activation requires a relatively smaller number of monocytes. 5. The mitogenic responses of T cells induced by kappa, lambda and iota CGN were significantly inhibited by cyclosporin A (CyA) treatment (250 ng/ml) and Con A and PHA responses were also inhibited by CyA addition. It was concluded that CGNs were newly found human T-cell mitogens, which is in sharp contrast with polyclonal B-cell activators in mice, and the mechanism of T-cell activation induced by CGNs was the same as that by Con A or PHA, though there may be another possibility of inhibition mechanism by CyA.

A comparison of regulatory cells from rabbit spleen and appendix

Both spleen and appendix of the rabbit contain two types of accessory cells that regulate the response of T-cells to concanavalin A. These accessory cells are found among non-T, non-B adherent cells and among B-cells. There is, so far, no evidence for a sequential interaction of these two cell types. In addition, there is an inhibitory adherent cell type in the appendix that interferes with the B-cell-regulated proliferative T-cell response.

Cyclosporin A inhibits thymus-dependent but not thymus-independent immune responses induced by dextran B512

We have compared previous studies of the immune response to dextran (Dx) B512 in thymus-deficient nu/nu and thymectomized, lethally irradiated, and bone marrow-reconstituted mice with those obtained with cyclosporin A (CyA) as a T-cell-inhibiting drug. Our data show that only immune responses to TD forms of Dx B512 are susceptible to suppression by CyA, whereas anti-alpha 1-6 and anti-DNP antibodies induced by high molecular weight dextran and DNP-native Dx, respectively, were not inhibited. Similar results were obtained when polyclonal responses were studied. The polyclonal response induced by another dextran preparation, the polyanion dextran sulphate (DxS), was inhibited by CyA to the same extent as polyclonal T-cell activation by T-cell mitogens.

Metabolism of androstenedione by guinea-pig peritoneal macrophages: synthesis of testosterone and 5 alpha-reduced metabolites

Androstenedione metabolizing enzymes present in guinea-pig peritoneal macrophages were investigated using tritium-labeled androstenedione as the substrate. We found that the metabolites of [3H]-androstenedione produced by these macrophages were testosterone, 5 alpha-androstane-3,17-dione, isoandrosterone, androsterone, 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol. The rates of metabolite formation remained linear as a function of time of incubation for approximately 30 min and with macrophage number up to 2 x 10(7) cells per ml. The formation of these metabolites in indicative that the following androstenedione metabolizing enzymes are present in guinea-pig peritoneal macrophages: 5 alpha-reductase, 3 alpha-hydroxysteroid oxidoreductase, 3 beta-hydroxysteroid oxidoreductase and 17 beta-hydroxysteroid oxidoreductase. It is possible, therefore, that the macrophage, in vivo, may play a role in the metabolism of blood-borne androstenedione to potent androgens. These hormones are important in the regulation of many biological processes, possibly including the activity of the macrophage itself.

Effect of malignant catarrhal fever virus infection on the immune response of rabbits to sheep red blood cells

Rabbits infected with African Malignant catarrhal fever virus mounted a depressed antibody response to sheep red blood cells compared to the antibody response of uninfected rabbits. Immunodepression was observed in rabbits immunised 0, 3, 5, 7 and 10 days after infection. Antibody response was not depressed in the rabbits immunised 1 day after infection. Despite the depressed antibody response to SRBC, the rabbits died with rising virus neutralising antibody to the virus. The possible causes of the immunodepression are discussed.

A mathematical model of B lymphocyte differentiation: control by antigen

A mathematical model of B lymphocyte differentiation, based on experimental results, has been developed. The model focuses on the role of antigen in initiating and regulating B cell differentiation while other mechanisms, acting in concert with antigen but the functioning of which can be circumvented under appropriate conditions, are not considered. The importance of presence of antigen at individual stages of B cell differentiation was studied in experiments with an easily metabolizable antigen. Immunocompetent cells (ICC), arising by antigen-independent differentiation of stem cells, are activated by antigen (they become immunologically activated cells--IAC). Excess of antigen drives IAC into the terminal stage (antibody-forming cells--AFC) thereby restricting proliferation. Exhaustive terminal differentiation results in tolerance. A low primary dose permits IAC to escape antigen; IAC proliferate and later give rise to resting memory cells (MC) which are amenable to reactivation. MC have higher avidity for antigen (due to higher affinity, number and density of receptors) and the effect of different doses of antigen on MC is diverse. A very low secondary dose induces tolerance, a medium dose secondary response, and the administration of a high dose of antigen also brings about tolerance. The model suggests that the fate of memory cells is controlled by the ratio R:Ag, of the number of immunoglobulin receptors on B cells (R) to the number of available antigenic molecules (Ag), low values R:Ag favouring stimulation to differentiation while high values of R:Ag favouring inactivation. A nonlinear system of ordinary differential equations, describing the development of the populations involved in antigen-driven B cell differentiation, was used to simulate experiments and good qualitative agreement was achieved.

Concanavalin A-induced chemiluminescence in rat thymus lymphocytes. Its origin and role in mitogenesis

1. The luminol-dependent chemiluminescence of rat thymocytes responding to concanavalin A can be resolved into glucose-dependent and glucose-independent portions. 2. The glucose-dependent portion, supported by D-glucose and D-mannose oxidation, is inhibited by catalase (200 microgram/ml), amobarbital (1 mM) and hexose analogues that block D-glucose uptake. Thus concanavalin A may activate, transiently, an NAD(P)H oxidase that utilizes reducing equivalents derived from the oxidation of exogenous glucose to give dismutation products of O2- (including H2O2) as its major products. 3. The glucose-independent portion is inhibited by eicosa-5,8,11,14-tetraynoic acid but not by indomethacin. It may therefore be associated with the conversion of hydroperoxy intermediates of arachidonic acid metabolism to hydroxy products by the lipoxygenase pathway. 4. Preincubation of thymocytes for 18 h in serum-free medium enhances the subsequent chemiluminescent response to concanavalin A severalfold and evokes the response at a lower threshold concentration. The incorporation of [3H]thymidine by preincubated cells is similarly enhanced at low doses of concanavalin A, whereas the response to optimal doses is unaltered. 5. Catalase does not inhibit the enhanced incorporation of [3H]thymidine obtained in response to concanavalin A, but instead amplifies the response to low doses in the same manner as preincubation.

On mechanisms of activation and restriction in T and B lymphocytes

The mechanism of MHC restriction is discussed with special reference to cytotoxic T lymphocytes reactive against hapten-modified self determinants. Effector cell specificity is considered to reflect the specificity of primary induction and recognition between T lymphocytes and immunogenic antigenic determinants. Mechanisms of activation and development of different specificity repertoires in T and in B cells are discussed, with special reference to those self determinants that direct specificity and serve as markers for self-nonself discrimination.

Effect of Vibrio cholerae neuraminidase on the mitogen response of T lymphocytes. I. Enhancement of macrophage T-lymphocyte cooperation in concanavalin-A-induced lymphocyte activation

Vibrio cholerae neuraminidase (VCN) enhances the immune response of lymphocytes in various systems, such as antigen- and mitogen-induced blastogenesis, mixed lymphocyte culture (MLC) and tumor-cell response. We used macrophage-depleted and reconstituted murine lymph-node T-cells to investigate the effect of VCN on macrophage-T-lymphocyte co-operation in Con-A-induced lymphocyte activation. In unfractionated lymph-node cells VCN enhanced the Con-A-induced lymphocyte activation as measured by 3H-thymidine (3H-dThd) incorporation. Removing macrophages from the cells resulted in a significantly diminished response. In addition the enhancing effect of VCN was greatly reduced. Reconstitution of the lymphocyte cultures with macrophages in increasing numbers and from various sources rstored the lymphocyte response and the enhancing effect of VCN. VCN proved to be most efficient in cultures reconstituted with normal peritoneal macrophages. Some effect was also observed using bone-marrow-derived (BM) macrophages. However, higher numbers of normal PE macrophages in the presence of VCN inhibited lymphocyte activation, and inhibition by thioglycollate-broth-induced macrophages was considerably increased by VCN. These results suggest that VCN acts by increasing the efficiency of macrophage-T lymphocyte interaction.

Impaired monocyte-mediated cytotoxicity in atopic dermatitis

Twenty-three adult patients with atopic dermatitis of different severity and extent all without present cutaneous infection were investigated for antibody-dependent cytotoxicity mediated by purified monocytes. Compared to a healthy control group the monocyte cytotoxicity was significantly decreased for patients with more widespread dermatitis. Eight patients with acute contact dermatitis and 13 patients with extrinsic asthma or allergic rhinitis showed normal cytotoxicity. Decreased monocyte cytotoxicity in atopic dermatitis was not related to the serum IgE level. In vitro cultivation of defective monocytes from atopics did not increase cytotoxicity, nor did normal monocytes preincubated with patient serum show abnormal function. In atopic dermatitis the total number of Fc receptor bearing monocytes was normal. However, the affinity of this receptor was lower than in normals. Serial studies are needed to establish whether reduced monocyte function is a basic pathophysiologic defect in atopic dematitis.

Rat dendritic cells function as accessory cells and control the production of a soluble factor required for mitogenic responses of T lymphocytes

Transformation of T lymphocytes, induced by treatment with periodate or with neuraminidase plus galactose oxidase, requires the participation of accessory cells. Procedures were developed for the fractionation of rat lymph node cells, by which most of the lymphocytes can be recovered as a major population of cells that do not respond to mitogenic stimulation unless accessory cells from a separated minor population are added. Further purification led to a 1000-fold overall increase in accessory activity per cell, with a 50-70% yield. The purest preparations were virtually free of macrophages and contained more than 90% typical dendritic cells. Maximum responses occurred at a ratio of only one dendritic cell per 200 periodate-treated lymphocytes. This evidence thus indicates strongly that in rats, dendritic cells--not macrophages--function as accessory cells. Further, the number of dendritic cells in a preparation governed the magnitude of the mitogenic response and was limiting in the case of unfractionated lymph node cells. In addition, when oxidized with periodate or with neuraminidase plus galactose oxidase, the dendritic cell served as a very potent indirect stimulator of untreated responder lymphocytes. Both functions of the dendritic cell appeared to lack species specificity, since mouse dendritic cells were very active when tested with rat responder lymphocytes. A soluble factor (accessory cell-replacing factor), produced by cultures of lymph node or spleen cells subjected to oxidative mitogenesis, enabled otherwise unresponsive mitogen-treated lymphocytes to respond. Dendritic cells were required for the production of this factor but may not be solely responsible for its production.

Activation of human peripheral blood lymphocytes: effect of concanavalin A and lipopolysaccharide on in vitro synthesis of DNA and immunoglobulins

We studied the interaction of lipopolysaccharide (LPS) and concanavalin A (Con A) with regard to IgM and IgG production in in vitro cultures of human peripheral blood lymphocytes (PBL). In our system LPS alone over a wide range of concentrations did not stimulate detectable IgM or IgG production, while Con A at optimal (6 microgram/ml) and suboptimal (0.6 microgram/ml) mitogenic concentrations induced synthesis of small amounts of Ig. A marked enhancing effect was present when both Con A and LPS were added to the cultures. The different doses of LPS has similar effects on both classes of Ig, and typical dose-response curves were obtained. To evaluate the cellular basis of this synergism, the effect on cell proliferation was studied under identical experimental conditions in normal subjects and patients with X-linked agammaglobulinaemia (X-LA). Parallel cultures were set up after monocyte depletion by adherence on Petri dishes. On day 3, increasing doses of LPS were associated with progressive decreases in 3H-thymidine (3H-TdR) incorporation. Similar results were obtained with normal lymphocytes and those from X-LA patients. Monocyte depletion did not substantially alter the lymphocyte response pattern. The preferential induction of helper activities, either directly by helper stimulation or indirectly by suppressor inhibition, is suggested as a possible mechanism of the interaction observed.

In vitro proliferative activity of spleen cells in mice infected with attenuated Salmonella typhimurium

Proliferative activity of cultured spleen cells obtained from mice 1 to 5 weeks after infection with attenuated strains of Salmonella typhimurium was examined in the presence or absence of lipopolysaccharide (LPS) or concanavalin A (Con A). Spontaneous uptake of 3H-thymidine (TdR) by cells taken from infected mice at the 2nd and 3rd weeks was obviously lower than that by cells from uninfected, control mice. Cells from infected mice at the 4th and 5th weeks also showed a lower proliferative response to LPS than that of the controls. However, the responses of the cells to Con A remained virtually unchanged during the entire period. Furthermore, the reduction of spontaneous 3H-TdR uptake by the cells could be achieved also by the injection of heat-killed instead of living organisms. The T- and B-lymphocyte populations of these spleen cells were examined by the dye exclusion cytotoxic test using rabbit anti-mouse T- and anti-mouse B-lymphocyte sera, respectively. There was some alteration of the populations in the cells, but it did not correlate with the reduction in 3H-TdR uptake. Results of experiments with cultured cells reconstituted with lymphocytes and macrophages isolated from spleen cells suggested that the spontaneous reduction of proliferative activity observed in cells taken from the infected mice could be attributed to the dysfunction of macrophages.

Characterization of human lymphocyte surface receptors for mitogenic and non-mitogenic substances

To compare the receptor patterns for mitogenic and non-mitogenic substances, surface glycoproteins of human lymphocytes were labelled with the lactoperioxidase-catalysed iodination technique and with a galactose oxidase-tritiated sodium borohydride technique. Labelled cells were detergent-solubilized, and the lysates were allowed to react with insolubilized purified mitogenic lectins, phytohaemagglutinin, leucoagglutinin and an insolubilized non-mitogenic lectin, oxidized leucoagglutinin. Lectin-reactive proteins were eluted with sodium dodecyl sulphate (SDS) buffer. Cell membrane components reactive with anti-lymphocyte globulin (ALG) were retrieved by indirect immunoprecipitation with protein-A-bearing staphylococcus Cowan I strain (SaCI). Lectin- and ALG-reactive proteins were analysed by SDS polyacrylamide gel electrophoresis. Iodinated glycoproteins regularly showed four major components with molecular weights of 120,000, 70,000, 60,000 and 43,000 daltons, respectively, on 7% gels. An additional broad peak in the molecular weight range 20,000--35,000 daltons was found on 10% gels. Tritiated glycoproteins also showed four major components with MW 120,000, 70,000, 60,000 AND 42,000, RESPECTIVely, which reacted with lectin and ALG. In addition, ALG reacted with some glycoproteins with MW between 150,000 and 230,000 daltons. On 10% gels additional lectin- and ALG-binding glycoproteins with MW around 30,000 daltons were found. The similarity in structures bound by mitogenic and non-mitogenic substances indicates that lymphocyte activation may depend on some property conferred by the mitogen.