Specific murine B-cell activation by synthetic single-and double-stranded polynucleotides

A focused immune response targeting the homotypic binding domain of the carcinoembryonic antigen blocks the establishment of tumor foci in vivo

Metastatic forms of cancers remain the main cause of death in cancer patients. In this study, we demonstrate that directing a sustained antibody response towards the homotypic binding function of CEA interferes with the implantation and development of tumor foci in CEA-expressing transgenic (CEA.Tg) mice. Specifically, vaccinating CEA.Tg mice with a recombinant, altered self-form of the CEA Ig V-like N domain led to the production of circulating IgG1 and IgG2a antibodies that inhibited CEA-mediated adhesion of murine carcinoma expressing CEA (MC38.CEA) and mediated antibody-dependent lysis of tumor cells. Moreover, vaccinated CEA.Tg mice were resistant to the development of tumor nodules in the lungs and the peritoneal cavity, suggesting that mounting a focused antibody response to the CEA N domain may represent a simple therapeutic strategy to control the establishment of metastatic foci in cancer patients.

Poly A:U-induced secretion of T-lymphocyte helper factors

In vitro exposure of mouse thymocytes to complexes of polyadenylic:polyuridylic acid (poly A:U) effected, within 6 h, the release of soluble factor(s) capable of nonspecifically enhancing IgM and IgG plaque-forming cells (PFCs) in in vitro primary and secondary spleen cell responses to burro erythrocytes. Poly A:U stimulation was, most likely, polyclonal, since production of soluble factor(s) occurred in the absence of antigen and in serum-free culture media. Poly A:U-induced soluble factor(s) were not capable of substituting for T cells but were dependent on T cells for the expression of PFC enhancement. These data support the hypothesis that the mechanism of poly A:U's adjuvant action is polyclonal stimulation of T cells, causing early induction and release of nonspecific, soluble PFC-enhancing factor(s).

Retinoic acid and polyriboinosinic acid act synergistically to enhance the antibody response to tetanus toxoid during vitamin A deficiency: possible involvement of interleukin-2 receptor-beta, signal transducer and activator of transcription-1, and interferon regulatory factor-1

Antibody responses to T cell-dependent antigens are reduced during vitamin A (VA) deficiency and restored by retinoids. To test whether retinoic acid (RA) and polyinosinic:polycytidylic acid (PIC), an inducer of interferons, can increase specific antibody production, VA-deficient rats were treated with all-trans-RA, PIC, or both at the time of primary immunization with tetanus toxoid. VA-deficient rats produced low primary and secondary anti-tetanus IgG responses (P<.001 vs. VA-sufficient controls). Both responses were increased synergistically by RA plus PIC (P<.0001). In VA-deficient spleens, mRNAs were low for interleukin (IL)-2 receptor-beta, interferon regulatory factor-1, and signal transducer and activator of transcription 1. Each, however, was induced by RA plus PIC (P<.0001 vs. controls). Conversely, IL-12 and IL-10 mRNAs were elevated in VA deficiency and were induced by PIC and suppressed by RA. Thus, RA plus PIC appears to be a promising combination for stimulating antigen-specific immunity. Several molecular factors identified here may partially account for the observed enhancement.

Adjuvant actions of polyclonal lymphocyte activators. V. Proliferation of macrophage colony-forming cells in the draining lymph node

We investigated the action of various polyclonal lymphocyte activators (PLA) on the proliferation of macrophage colony-forming cells in vivo at the local site. As PLA, Klebsiella pneumoniae 03 lipopolysaccharide (K03 LPS), Escherichia coli 0111 lipopolysaccharide (E. coli LPS), dextran sulfate (DS), concanavalin A (Con A), phytohemaggulutinin (PHA), polyadenylic-polyuridylic acid (poly(A:U], polyinosinic-polycytidylic acid (poly(I:C], and pokeweed mitogen (PWM) were used. All PLA tested acted to proliferate macrophage colony-forming cells in the draining lymph node at a late stage after subcutaneous injection. The order of strength of this action of PLA was K03 LPS greater than E. coli LPS greater than Con A greater than DS greater than PHA, PWM, poly(I:C), and poly(A:U), which corresponded to the order of strength of their adjuvant action in initiating helper-T-cell response to subcutaneous injection of aggregate-free bovine gamma-globulin. The detailed relationship between the proliferation of macrophage colony-forming cells and the adjuvant action of PLA is discussed.

Induction of ornithine decarboxylase in mouse tissues following the injection of mitogenic substances. Enhancement by actinomycin D

Experiments were carried out to study the mechanism of the induction of ornithine decarboxylase (ODC) in mouse tissues by the injection of a lipopolysaccharide (LPS). In addition to LPS, various mitogenic substances, such as concanavalin A, pokeweed mitogen, polyI:polyC and a phorbol diester, induced ODC in the liver and the spleen of mice at 4.5 hr after injection. Non-mitogenic immuno-stimulants or inflammatory agents, such as zymosan, carrageenan, N-acetylmuramyl-L-alanyl-D-isoglutamine, glycogen, D-galactosamine and interferon, did not induce the enzyme. ODC induction by LPS in C3H/HeJ mice, the lymphocytes and/or macrophages of which are known to be less responsive to LPS, was much less than in C3H/He and ddI mice. ODC induction by LPS was suppressed by dexamethasone and cycloheximide. Actinomycin D did not suppress ODC induction by LPS but, rather, enhanced it. These results suggest that (1) lymphocytes and/or macrophages may participate in the induction of ODC by mitogenic substances as well as by LPS, (2) ODC may be induced by mitogenic substances without the synthesis of RNA, and (3) the translation of existing RNA may be accelerated by actinomycin D.

Induction of hypoglycaemia and accumulation of 5-hydroxytryptamine in the liver after the injection of mitogenic substances into mice

Various mitogenic substances (concanavalin A, pokeweed mitogen, polyI : polyC and a phorbol diester), as well as lipopolysaccharides (LPS or endotoxins), produced hypoglycaemia after being injected into mice. However, non-mitogenic immuno-stimulants (zymosan, carrageenan, an adjuvant peptide and interferon) did not induce hypoglycaemia. All of the mitogenic substances also induced an increase in 5-hydroxytryptamine (5-HT) in liver, but the non-mitogenic substances did not have this effect. The time course of the development of hypoglycaemia was similar to that of the increase in liver 5-HT. The dose-dependence of the hypoglycaemia induced by LPS was similar to that of the increase in liver 5-HT. In C3H/HeJ mice, the macrophages and/or lymphocytes of the mice are known to be less responsive to LPS, and both the LPS-induced hypoglycaemia and increase in 5-HT were less in these mice than in control mice (C3H/He and ddI mice). These results suggest that macrophages and/or lymphocytes may participate in the induction of hypoglycaemia and the increase in 5-HT induced by mitogenic substances and LPS. A possible correlation between hypoglycaemia and the increase in hepatic 5-HT is discussed, although the relationship is not substantiated.

Induction of histidine decarboxylase in mouse tissues by mitogens in vivo

Various types of mitogenic substances, such as a Escherichia coli lipopolysaccharide (LPS), concanavalin A (Con A), pokeweed mitogen, polyI:polyC (a synthetic double-stranded RNA) and 12-O-tetradecanoylphorbol-13-acetate (a component of croton oil), induced histidine decarboxylase (HDC) in the liver, spleen and lung of mice at 4.5 hr after injection. Other inflammatory agents without mitogenic activity, such as zymosan, carrageenan, glycogen, D-galactosamine and N-acetyl-muramyl-L-alanyl-D-isoglutamine, did not induce the enzyme. Both LPS (a B-cell mitogen) and Con A (a T-cell mitogen) induced HDC also in nude mice that lack T-cells, indicating that T-cells are not required for HDC induction by mitogens. C3H/HeJ mice, which are LPS-low responder mice in various immunological tests, were quite a bit less responsive to LPS also in the HDC induction. These results show that mitogens with different properties can induce HDC as a common characteristic. On the basis of these results, the possible participation of macrophages in the process of HDC induction by mitogens was discussed.

Flow cytometric analysis of in vivo activation of murine spleen cells

The in vivo effects of two polyclonal immune stimulators were studied in several strains of mice by analyzing the percentages of cells in various phases of the cell cycle by flow cytometry. Both lipopolysaccharide (LPS) and polyriboinosinic X cytidylic acid (rI X rC) were capable of inducing an increase in the percentage of cells undergoing DNA synthesis (S phase) in the spleens of several mouse strains. The response to both LPS and rI X rC was maximal between days 3 and 5 following injection. Optimal in vivo responses to LPS occurred at 3-30 micrograms, and to rI X rC at 100 micrograms; however, responses were observed over a broad dose range. No similar increase in S-phase cells was observed following injection of non-mitogenic T-independent antigens. Specific antibody was also measured after in vivo administration of rI X rC. There was a dissociation between the ability of an injection to induce specific antibody and to induce proliferation. These studies extend our knowledge of in vivo lymphocyte activation, and provide a basis for a detailed analysis of lymphocyte activation following a variety of immune modulators in vivo.

Effects of NPT 15392 in vitro on human leukocyte functions

NPT 15392 (Erythro-9 (2-hydroxy-3 nonyl) hypoxanthine), a novel heterocyclic immunomodulatory compound, was analyzed over a broad concentration range on a variety of human blood leukocyte functions in vitro. NPT 15392 augmented mitogen-induced lymphocyte transformation in a variable fashion; lymphocytes from 9 of 24 individuals showed significant stimulation with phytohemagglutinin at 0.01 microgram/ml of NPT 15392, and 3 of 14 and 3 of 3 showed similar augmentation with concanavalin A and pokeweed mitogen, respectively. NPT 15392 above 10 microgram/ml inhibited mitogen responses and did not itself stimulate cell division. NPT 15392 also augmented responses of lymphocytes to antigenic stimulation with Candida and Staphylococcus antigens, purified protein derivative, and allogeneic cells in a variable manner. When observed, stimulation occurred at 0.01-1 microgram/ml of NPT 15392 for Candida and Staph. and at 0.01 microgram/ml with PPD and allogeneic cells. NPT 15392 (0.01-1 microgram/ml) consistently induced suppressor cell function alone and in combination with concanavalin A. This effect is apparently mediated by T lymphocytes since suppression was not mediated by interferon, prostaglandin or histamine. In addition, NPT 15392 (0.01-10 microgram/ml) significantly augmented "active" T cell rosettes. NPT 15392 over a broad concentration range and in the presence and absence of interferon did not stimulate natural killer cell activity or antibody-dependent cellular cytotoxicity. The data indicate that NPT 15392 is a modulator of such T lymphocyte functions as proliferative response to antigen and mitogen, suppressor activity and receptor display. Such activities imply potential therapeutic use in immunodeficiency related to defects of the thymus and thymus-derived lymphocytes.

The glycoprotein isolated from vesicular stomatitis virus is mitogenic for mouse B lymphocytes

The glycoprotein (G protein) of VSV was purified from the intact virion by Triton X-100 extraction. The isolated G protein has been shown to be a T cell-independent, B lymphocyte mitogen and polyclonal activator. Neither G protein nor the intact virion are stimulatory for murine T lymphocytes. The greater the density of G protein in lipid vesicles or the degree of aggregation of isolated G protein, the more highly stimulatory it is for murine splenocytes. As G protein is spread out in artificial vesicles, it becomes less mitogenic. It is probable that other viral components are also stimulatory since the Triton-insoluble pellet and VSV from which the G protein has been enzymatically removed retain mitogenic activity. To out knowledge, this is the first time a purified viral component has been demonstrated to be lymphocyte mitogen.

Differences in the B cell interferon responses to lipopolysaccharide and poly I:C

Two polyclonal B cell activators, lipopolysaccharide (LPS) and poly I:C, have been used to induce interferon (IFN) production by murine B cell populations. The results show that splenic B cell-enriched fractions, isolated by wheat germ agglutination followed by C-dependent anti-Thy 1.2 cytolysis, respond to treatment with poly I:C + DEAE-dextran by IFN production at levels comparable on a per cell basis to unfractionated spleen cells. By contrast, the LPS-stimulated IFN response of these same B cell fractions is either undetectable or substantially lower than that of spleen cells; although the B cell fractions appear fully capable of LPS-induced proliferation. Consistent with this pattern of splenic B cell IFN responses, two antibody-secreting hybridoma lines and two myeloma cell lines (including the parental myeloma of the hybrid) can be stimulated by poly I:C + DEAE-dextran to produce IFN; yet these same B cell lines do not synthesize IFN in response to LPS at doses from 1-100 micrograms/ml. The level of poly I:C-induced IFN secreted by the hybridomas are approximately 10-fold greater than that produced by the unfused parental myeloma cells. Not only do these results directly demonstrate that murine lymphocytes of the B cell lineage produce IFN in response to the B cell activator poly I:C, but these observations also strongly suggest that the IFN responses of the B cell tumor lines model the IFN producing capacity of splenic B cells. Moreover, since the hybridoma cell lines and one of the myeloma lines synthesize specific antibody molecules, these observations show that the progeny of a single B cell clone can synthesize and secrete both IFN and immunoglobulin.

Activation of mouse lymphocytes by vesicular stomatitis virus

Vesicular stomatitis virus (VSV) is a mitogen for mouse spleen cells, and infectious virus is not required for mitogenesis. At concentrations between 10 and 100 microgram per culture, VSV stimulated DNA synthesis and blast transformation. Maximal activation by VSV occurred 48 h after culture initiation. Spleen cells depleted of T-lymphocytes by treatment with anti-Thy 1.2 and complement and those obtained from congenitally athymic BALB/c nu/nu mice were activated by VSV, suggesting that VSV is a B-cell mitogen. Activation of spleen cells was independent of the host in which the virus was grown, since VSV grown in BHK-21, HKCC, or MDBK cells was mitogenic. The mitogenesis was specific for VSV, since MDBK cell-grown WSN influenza virus was not a mitogen in this in vitro activation system, VSV-specific antibody prevented VSV mitogenesis, and VSV was mitogenic for spleen cells from C3H/HeJ mice which were resistant to mitogenesis by endotoxin.

Induction of partial chimerism in nonirradiated B-lymphocyte-deficient CBA/N mice

Nonirradiated B-lymphocyte-deficient CBA/N mice given T6T6 chromosome-marked normal CBA/CaHN spleen cells became lymphoid chimeras exhibiting donor-type mitoses. Normal CBA/CaHN recipients did not exhibit significant numbers of donor-type mitoses. The lymphoid cell chimerism in the CBA/N host appeared in spleen, lymph nodes, and Peyer's patches, but not in marrow or thymus. Stimulation of CBA/N-recipient spleen cells in vitro suggested that the chimerism involved donor T6T6 cells which were responsive to the B-lymphocyte mitogen, lipopolysaccharide, but not to the T-lymphocyte mitogen, phytohemagglutinin. These data indicate that stable, long-term chimerism of a specific class of lymphocytes is possible in nonirradiated, B-lymphocyte-deficient CBA/N mice.

The effects of purified mitogenic proteins (Pa-1 and Pa-2) from pokeweed on human T and B lymphocytes in vitro

Purified proteins (Pa-1 and Pa-2) from pokeweed have been compared with commercial pokeweed mitogen (PWM-G) and other mitogens in their ability to stimulate human lymphocytes. With cultures of T and B cells separated from tonsil lymphocytes, thymidine uptake, blast transformation and immunoglobulin (Ig) synthesis have been measured. IgM and IgG was measured in supernates of stimulated cultures by radioimmunoassay. Pa-1, Pa-2 and PWM-G were found to be potent mitogens for unseparated tonsil lymphocytes or nylon column purified T cells. Pa-2 was found to be active at lower concentrations than Pa-1, and PWM-G was less potent than the purified mitogens. These three mitogens all stimulated unseparated lymphocytes to secrete large quantities of Ig (20-100 mug/ml) during 7 days in culture. With increasing amounts of mitogens severe decreases in immunoglobulin synthesis were observed at day 6 even with doses which were still optimal for stimulation of thymidine uptake at days 3 and 6. With purified B cells (less than 2% T cells) Pa-1 was the best mitogen for thymidine incorporation. However, the secretory response was very variable. In some experiments B cells did not secrete Ig in response to mitogens; in others Pa-1 was clearly more effective at stimulating secretion than Pa-2 or PWM-G and in some experiments B cells were stimulated by all three. In one experiment Pa-1 stimulated prolymphocytic leukaemia cells to blast transformation and the secretion of IgM. It is concluded that Pa-1, Pa-2 and PWM-G are much better activators of Ig synthesis in human cultures than either PHA or LPS and that Pa-1 is the most reliable B-cell stimulant of the three.

Patterns of B-lymphocyte gene expression elicited by lipopolysaccharide mitogen

When large proportions of B lymphocytes from the murine spleen are stimulated in vitro by bacterial lipopolysaccharide (LPS) B lymphoblasts with small amounts of intracellular immunoglobulin (Ig) and plasmablasts with large amounts of intracellular Ig concomitantly proliferate. It is likely that B lymphocytes are heterogeneous and LPS activates B cells to express their predetermined functional capacity since bromodeoxyuridine does not inhibit the initiation of Ig synthesis in plasmablasts, and Ig synthesis starts before these cells complete their first mitosis. The results suggest that LPS is a potent polyclonal activator (of a B-cell subset) but it is not a differentiation factor in the sense that it is unable to determine whether its target cell develops extensive endoplasmic reticulum or follows a different pathway. The results do not exclude that modulation of B cells' genetic programming might take place during T cell-dependent B-lymphocyte activation. The observed B-cell heterogeneity offers a possible explanation for the concomitant emergence of B memory cells and antibody producers during the early phase of immune responses in vivo.

Enumeration of polyclonal mitogen-responsive cells in different lymphoid tissues of the mouse

The relative number of cells capable of responding to Con A, PHA and LPS in the spleen, blood, lymph node and Peyer's patches of CBA mice has been quantified by means of a cytological analysis technique. No difference has been found between Con A- and PHA-responsive cells in spleen and lymph node. The lymphoid tissues of T cell-deprived mice have a reduced content of PHA responsive cells, but LPS responsiveness is within normal limits. Pretreatment of peripheral lymphocyte populations with high concentrations of anti-O antiserum and complement abolishes the response of the treated cells to PHA, but not to LPS, whereas similar treatment with a cytotoxic anti-immunoglobulin serum, which has no effect on PHA-responsive cells, only partially reduces the response to LPS. The results for mitogen responsiveness are discussed with reference to other methods of quantifying T and B cells using cell-surface markers.

Blastogenic response of Toxoplasma-infected mouse spleen cells to T- and B-cell mitogens

In order to differentially test the function of lymphocytes in Toxoplasma gondii-infected mice, the in vitro blastogenic response of spleen cell cultures to non-specific mitogens was studied. Phytohaemagglutinin (PHA) and concanavalin A (Con A) stimulation were used as tests of thymus-dependent lymphocyte (T cell) function and bacterial endotoxin lipopolysaccharide (LPS) was used as a probe of bursal equivalent lymphocyte (B cell) function. For the first 3 weeks following T. gondii infection, the uptake of tritiated thymidine ([3H]TdR) by spleen cells cultured with all three mitogens was markedly reduced in comparison to the uptake in spleen cells from uninfected control mice. Thereafter, the response to LPS returned to normal while stimulation by the T-cell mitogens (PHA and Con A) remained depressed. It is postulated that T. gondii infection either: (1) diluted out T cells in the spleen with unreactive cells; (2) modified T cells in such a way that they were less responsive to mitogens; (3) depleted the peripheral lymphoid tissues of T cells; (4) induced non-specific suppressor cells, which inhibited the T-cell function assays; or (5) activated macrophages which depressed T-cell function non-specifically.

X-linked B-lymphocyte immune defect in CBA/N mice. II. Studies of the mechanisms underlying the immune defect

The mechanisms underlying the X-linked thymus-independent (B) lymphocyte functional defect in the CBA/N (CN) mice and their F1 progeny were studied. Immune defective mice were unable to respond to the T-independent antigen 2,4-dinitrophenyl-lysyl-derivative of Ficoll (DNP-lys-Ficoll) but were able to form antibody against the highly cross-reactive hapten (trinitrophenyl) when it was coupled to an erythrocyte carrier. Immune defective CN X DBA/2N (DN) F1 male mice, which do not normally respond to T-independent antigens, were able to respond to both polyribosinic-polyribocytidylic acid and DNP-lys-Ficoll after the administration of CN X DN F1 female spleen cells even if these cells had been depleted of T lymphocytes. In addition, it was shown that the inability of the CN mice and their F1 progeny to respond to T-independent antigens was not due to an intrinsic abnormality of their microenvironment or the suppressive actions of a T lymphocyte. Our data present evidence that the X-linked defect in the CN mice is due to an intrinsic defect in B-lymphocyte development.

Human T-cell heterogeneity as delineated with a specific human thymus lymphocyte antiserum. In vitro effects on mitogen response mixed leukocyte culture, cell-mediated lymphocytotoxicity, and lymphokine production

Human peripheral blood lymphocytes (PBL) were evaluated by their responses to phytohemmagglutinin (PHA-P), concanavallin A (con-A), and pokeweed mitogen (PWM), both before and after treatment with an antiserum against human thymic lymphocyte antigens (HTLA) that had been made T-cell-specific by multiple absorptions with immunoglobulin EAC-positive lymphoblast cell lines (B cells). Cells treated with HTLA were examined for their ability to react in a mixed lymphocyte culture (MLC) and to form killer cells in a cell-mediated lymphocytotoxicity (CML) system. Sensitized cells were also examined for their ability to respond to purified protein derivative (PPD) by blastogenesis, migration inhibitory factor release (MIP), and lymphotoxin (LT) production, both before and after treatment with HTLA and complement. The HTLA was in itself highly stimulatory to PBL. However, with the addition of complement and subsequent cell destruction, a marked decrease in its stimulatory response was noted. PBL treated with HTLA and complement exhibited marked inhibition of responsiveness to con-A with little decrease in PHA-P -OR PWM stimulation except at very high concentration of HTLA. MLC reaction was inhibited only when responder cells were treated with HTLA + C'. Treatment of stimulator cells with HTLA + C' did not significantly alter the MLC response. The HTLA + C'-treated cells failed to form killer cells in the CML reaction and inhibited PPD-induced blasto-genesis from PPD-sensitized individuals; however, treatment of sensitized cells with HTLA + C' had little effects on the release of MIF and LT. It is suggested that subpopulations of T-cells carry surface antigens that bind with this specific antisera, and that the con-A-responsive cells, the responder cells in the MLC, and killer T-cells comprise a separate subset from cells responding to PHA-P or PWM, OR THE MIF-and LT-producing cells.

X-linked B-lymphocyte immune defect in CBA/HN mice. I. Studies of the function and composition of spleen cells

A study of the composition and functional properties of spleen cells from the immune deficient CBA/HN mice and their F1 progeny is reported. While abnormalities were seen in both the numbers and function of thymus-independent (B) lymphocytes, all studies involving thymus-dependent (T) lymphocytes were normal. The X-linked nature of the immune defect in these mice was therefore attributed to abnormal or absent B lymphocytes. The possible nature of this defect and the similarity of the immune defect in these mice to certain human X-linked immunodeficiency diseases are discussed.

The immunological properties of haptens coupled to thymus-independent carrier molecules. III. The role of the immunogenicity and mitogenicity of the carrier in the induction of primary IgM anti-hapten responses

Hapten (DNP-lys) conjugates of two putatively nonimmunogenic polymers, hyalutonic acid and poly-gamma-D-glutamic acid, induce significant primary IgM anti-DNP responses in C3H mice. Preparations of various immunogenic (Type 3 pneumococcal polysaccharide (SIII), levan, E. coli lipopolysaccharide) and nonimmunogenic (hyaluronic acid and poly-glutamic acid) polymers were tested for their ability to act as polyclonal mitogens in vitro. In serum-containing spleen cell cultures, only lipopolysaccharide stimulated substantial cell proliferation. In serum-free medium, and using high specific activity [3H]thymidine, lipopolysaccharide, levan, SIII and to a lesser degree hyaluronic acid induced significant thymidine incorporation. However, under the latter conditions cell survival and proliferation were much less impressive. There was no apparent correlation between the capacity of various polymers to induce lymphocyte proliferation and their "potency" as carriers for the generation of a primary IgM anti-DNP response. Furthermore while low doses of lipopolysaccharide elicited "polyclonal" antibody formation in vivo, high doses of SIII, levan and hyaluronic acid did not. These results indicate that T cell-independent B cell triggering is dependent on the polymeric nature of the antigen, and that polymers need not be immunogenic or mitogenic to act as carriers for the induction of primary IgM anti-hapten antibody responses.