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B L Pope

Publications and source records attributed to B L Pope.

At least 37 records · Page 2Linked to original sources
PubMed1988

Secretion of a suppressor cell inducing factor by an interleukin 3-dependent cell line with natural cytotoxic activity. III. Comparison with other interleukin 3-dependent cell lines.

We previously described the interleukin 3 (IL-3)-dependent cell line, M1-A5, which has both natural cytotoxic (NC) and suppressor cell activities, the latter of which is mediated, in part, by the release of two cytokines which activate suppressor cells from unprimed lymphoid precursor cells. In this study we have compared the M1-A5 cell line with four other IL-3-dependent cell lines to determine whether these dual activities are universally associated with IL-3 dependence and to test the hypothesis that there is a direct relationship between the cytotoxic and the suppressive activities. The cell lines tested were a bone marrow derived Dexter culture derived line (FDC-P1), two Moloney leukemia virus induced leukemias (DA-1 and DA-3), and a mast cell line (PT18(A17]. All lines were dependent on IL-3 for survival but FDC-P1, DA-1, and DA-3 showed varying degrees of short-term proliferation in granulocyte-macrophage colony stimulating factor (GM-CSF). The cell lines all expressed asialo GM1 and Ly-5 surface markers but differed with respect to other markers. DA-1 expressed MAC-1, FDC-P1 and DA-3 expressed Thy-1, and PT18(A17) expressed receptors for the Fc portion of IgE. The cell lines varied greatly in their cytotoxic activity against WEHI-164. FDC-P1, DA-1, and PT18(A17) had low NC activity. DA-3 had consistently high activity, greater than that seen with M1-A5 cells. However, none of the cell lines secreted constitutively a suppressor cell inducing factor (SIF). In addition, it was demonstrated that recombinant murine TNF did not activate suppressor cells capable of inhibiting antibody synthesis and that anti-TNF did not block SIF activity, thus suggesting that TNF contamination of the M1-A5 derived SIF preparation is not responsible for the induction of suppressor cells. We conclude that suppressor cell inducing factors are not universally secreted by IL-3-dependent cell lines, that there is no correlation between NC and SIF activity, and that the dual activities of M1-A5 cells are not mediated by TNF.

Animals↗
PubMed1987

Cyclic AMP as the second messenger for prostaglandin E in modulating suppressor cell-activation by natural suppressor/cytotoxic cells.

The M1-A5 cell line, isolated from the spleen of a tumor bearing mouse, has been shown to secrete a suppressor cell-inducing factor (SIF) which activates suppressor cells from the spleen cells of unprimed mice. In an earlier publication we demonstrated that prostaglandins of the E series (PGE) regulate the release of SIF from M1-A5 cells. In the present study we provide evidence that cyclic adenosine 3',5'-monophosphate (cyclic AMP) is the second messenger for PGE in regulating the release of SIF from M1-A5 cells. Our data show that PGE1 and PGE2 stimulate cyclic AMP production by M1-A5 cells. Furthermore, we show that drugs which: (1) elevate cyclic AMP levels (dibutyryl (db) cyclic AMP), (2) inhibit the breakdown of cyclic AMP (theophylline), or (3) stimulate adenylate cyclase (isoproterenol and histamine) all restored suppressor cell activation by M1-A5 cells in which PG synthesis had been blocked by acetylsalicylic acid (ASA). Thus, these results are consistent with the hypothesis that cyclic AMP is the second messenger for PGE in modulating the release of SIF from M1-A5 cells.

Animals↗
PubMed1987

Secretion of a suppressor cell-inducing factor by an interleukin 3-dependent cell line with natural cytotoxic activity. II. Range, potency, and kinetics of suppressive activity.

We have shown previously that the interleukin 3 (IL 3)-dependent, M1-A5 cell line has natural cytotoxic (NC) activity and secretes a small molecular weight factor which activates suppressor cells capable of inhibiting the in vitro generation of antibody forming cells (PFC). In this paper, we show that the M1-A5 cells are capable of suppressing the generation of both PFC and cytotoxic T cells (CTL) as well as the proliferative response in a mixed lymphocyte reaction (MLR). Very little suppression of Concanavalin A (Con A)-stimulated proliferation is seen. Suppression is seen with as few as 10(2) M1-A5 cells, a 10(-4) dilution of a cell-free supernatant from the M1-A5 cells, or as few as 10(4) suppressor cells activated by the suppressor cell inducing factor (SIF) secreted by the M1-A5 cell line. Kinetic studies show that, in all cases, the cells or suppressive factors must be present in the initial 24 to 48 h of the culture for significant suppression. In contrast, a second IL 3-dependent cell line FDC-P1 is directly suppressive, but this suppression is clearly due to a different mechanism, since cell-free supernatants are not inhibitory and do not activate suppressor cells.

Animals↗
PubMed1987

Induction of suppression by a murine nonspecific suppressor-inducer cell line (M1-A5). III. Partial purification of the suppressor cell-inducing factors.

The cause of the state of anergy which often accompanies advanced tumor growth has been attributed to several factors, including nonspecific suppressor cells capable of suppressing humoral and cell-mediated responses. Induction of suppressor cells in tumor-bearing hosts has been attributed to the release of immunoregulatory factors by the tumor, as well as by the host's own lymphoid cells. Several such "suppressor cell-inducing factors" have been described. However, in only a few cases has the inducing material been characterized. We have recently reported the existence of a suppressor cell inducing factor (SIF) in the 18 hr culture supernatant of spleen cells from mice bearing an advanced M-1 fibrosarcoma. Our aim was to characterize SIF, both biochemically and mechanistically. In order to purify the inducing factor, as well as to dissect the cellular and molecular events that occur as a result of suppressor cell activation, we isolated the M1-A5 cell line from the spleen cells of a mouse bearing an advanced M-1 fibrosarcoma. Induction of suppressor cells by supernatants from M1-A5 cells closely resembled the situation seen with the whole spleen cells. In both cases: 1) an inducing factor with an estimated Mr less than 12 kDa was found, and 2) the release, but not the effector function, of the inducing factor was prostaglandin-dependent. The 18 hr culture supernatant of M1-A5 cells was used as the source of the inducing factor and suppressor cells were activated by exposure of normal spleen cells to the inducing factor for 4 hr. The nature of the inducing factor was investigated by subjecting the M1-A5 culture supernatant to molecular weight sieving on Sephadex G-100 medium. The results showed that M1-A5 supernatants contained a high- (Mr 70 kDa) and a low- (Mr 5.5 kDa) molecular weight factor, which were termed SIF alpha and SIF beta, respectively. SIF alpha and SIF beta were further purified by ion exchange chromatography. SIF beta bound to QAE-Sephadex A-25 and was eluted in a single peak. However, SIF alpha displayed heterogeneity with respect to binding to DEAE-Sephacel, as SIF activity was seen in the void volume as well as in fractions eluted from the anionic exchanger. Mechanistically, we demonstrate that the induction of suppressor cells by SIF alpha and SIF beta is genetically non-restricted. In addition, we show that SIF alpha and SIF beta suppress the in vivo antibody response to sheep red blood cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Induction of suppression by a murine nonspecific suppressor-inducer cell line (M1-A5). II. The role of prostaglandins.

A murine nonspecific suppressor-inducer cell line (M1-A5) was generated from the spleen cells of a mouse bearing an advanced methylcholanthrene-induced fibrosarcoma. We previously demonstrated the capability of M1-A5 cells to activate suppressor cells from the spleen cells of unprimed mice. We demonstrate here that induction of suppression by M1-A5 cells was blocked by acetylsalicylic acid (ASA) and ibuprofen at concentrations which block prostaglandin (PG) synthesis. Maximal blockade of the induction of suppression by M1-A5 cells was seen when ASA was added at the initiation of culture, and it required inhibition of PG synthesis at the level of the inducer (M1-A5 cells) population. However, ASA blockade of suppressor cell activation by M1-A5 cells was not due to ASA acetylating suppressor-inducing factor. Exogenously added PGE1, PGE2, and PGI2, but not PGF2 alpha or PGD2, were able to restore the inducing capability of M1-A5 cells, which had been blocked by ASA. However, PGE1, PGE2, or PGI2 did not reconstitute an inactive suppressor-inducing factor. These results suggest that PG act to modulate the release of suppressor-inducing factor from M1-A5 cells.

Alprostadil↗
PubMed1986

Secretion of a suppressor cell inducing factor by an interleukin-3 dependent cell line with natural cytotoxic activity.

This report describes the morphology, surface markers, growth requirements, and functional activity of the M1-A5 cell line, which was established by the limiting dilution of spleen cells from a mouse bearing a large methylcholanthrene-induced fibrosarcoma. The M1-A5 cells share many of the morphological features of large granular lymphocytes and, in addition, express asialo GM1 and Ly-5 surface markers which are commonly found on natural killer cells (NK) cells. There is no expression of T-cell differentiation antigens, surface immunoglobulin, or the granulocyte/macrophage marker, MAC-1. M1-A5 cells are dependent on exogenous growth factor(s) for survival and will proliferate if cultured in interleukin 3 (IL-3), but not in interleukin 1 (IL-1), interleukin 2 (IL-2), or granulocyte/macrophage colony stimulating factor (GM-CSF). In addition, the M1-A5 cells do not absorb IL-2. Despite their morphology and surface characteristics, the M1-A5 cells do not lyse NK targets such as YAC-1 and RLM1 in 4- or 18-hr cytotoxic assays but do lyse the natural cytotoxic (NC) susceptible target, WEHI-164, and to a very small extent, the M-1 fibrosarcoma cells, in an 18-hr assay. Thus they exhibit NC-like cytotoxic activity. In addition, the M1-A5 cells secrete a small molecular weight factor which activates suppressor cells capable of inhibiting antibody synthesis by cocultured syngeneic spleen cells.

Animals↗
PubMed1986

Requirement for prostaglandin E1 (PGE1) for the secretion of suppressor cell inducer factors by spleen cells of tumor-bearing mice.

We have demonstrated previously that spleen cells from mice bearing M-1 fibrosarcomas release low molecular weight factors capable of activating suppressor cells from unprimed normal spleen cells. Using Marbrook vessels to separate inducer and precursor populations, we found in the previous paper that cyclooxygenase inhibitors blocked the activation of suppressor cells and that this activation could be restored by exogenous PGE1. In this paper we have examined the site of action of the prostaglandins in the activation of suppressor cells. To do so, we tested cell-free supernatants from cultured spleen cells of tumor-bearing mice (inducer cells) for the ability to activate suppressor cells from unprimed normal spleen cells (precursor cells). Supernatants from acetyl salicylic acid (ASA) treated inducer cells did not activate suppressor cells and exogenous PGE1 could not restore the activity of this supernatant. In contrast, if inducer cells were treated with ASA and then incubated with PGE1, the supernatant was capable of activating suppressor cells. No role for prostaglandins at the level of the precursor cells or the effector suppressor cells was seen. These data suggest that the inducer cells in tumor-bearer spleens require prostaglandins for the release of an inducer factor but that prostaglandins are not required for the action of this factor on the precursor cells or for the effector function of the activated suppressor cells.

Alprostadil↗
PubMed1986

Activation of suppressor cells by low molecular weight factors secreted by spleen cells of tumor-bearing mice: modulatory role of prostaglandins.

We have shown previously that the spleens of mice bearing large M-1 fibrosarcomas contain inducer cells which secrete dialysable factors which activate suppressor T cells from unprimed, normal precursor spleen cells. Once activated, the suppressor cells inhibit the in vitro antibody synthesis of cocultured syngeneic splenocytes stimulated by T cell dependent antigens. In this paper we have examined the possibility that prostaglandins are involved in the activation process. Inducer and precursor cells were cultured in Marbrook vessels in chambers separated by dialysis membranes. Using this procedure, suppressor cells were activated following 12 h of culture but were not detectable after 6 h. The cyclooxygenase inhibitors, indomethacin, acetyl salicylic acid (ASA), and ibuprofen all prevented the activation of suppressor cells in a dose dependent manner. Prostaglandin (PG) E1, but not PGF2a or PGD2, restored the activation of suppressor cells in cultures containing the cyclooxygenase inhibitors. Restoration of suppressor cell activation was seen with 1 X 10(-7) M PGE1 but no activation of suppressor cells was seen in control cultures containing up to 1 X 10(-5) M PGE1. In addition, cultured spleen cells from tumor-bearing mice did not secrete higher quantities of PGE than did cells from age and sex matched normal mice. These data suggest that PGE has a modulatory rather than a direct role in the activation of suppressor cells by inducer factors from tumor-activated inducer cells.

Alprostadil↗
PubMed1986

Kinetic analysis of the inhibition of natural killer (NK) activity by multiple populations of tumor-activated suppressor cells.

Previous studies have shown that the progressive growth of the M-1 fibrosarcoma in DBA/2J mice is associated with the activation of suppressor cells which inhibit both mitogen-induced proliferative responses and antibody synthesis. In this study, we have analyzed the effect of tumor growth on NK cell activity. Mice in the advanced stages of tumor growth did have a significant depression in NK activity, and this depression could not be overcome by the injection of the interferon inducer, polyinosinic-polycytidylic acid (Poly I:C). The decline in NK activity was associated with the presence in the spleens of suppressor cells capable of inhibiting the NK activity of spleen cells from Poly I:C-treated syngeneic mice. In order to characterize the suppressor cells, we used a combination of negative selection procedures and kinetic analysis. These studies demonstrated that the spleens of tumor-bearing mice contained two distinct populations of suppressor cells which were not evident in normal mice. One population was non-adherent to nylon wool, Thy-1-, non-phagocytic, did not bind target cells, and had a non-competitive mechanism of suppression. The second population was adherent, Thy-1-, phagocytic, and had a competitive mechanism of suppression. In addition, the spleens of both normal and tumor-bearing mice contained an adherent, non-competitive suppressor cell population which was enriched following negative selection procedures removing T cells or phagocytic cells.

Animals↗
PubMed1986

Production of interferon by peripheral blood mononuclear cells from normal individuals and patients with chronic lymphocytic leukemia.

Peripheral blood mononuclear cells (PBMC) from normal individuals were studied to identify which cells produce alpha-interferon (IFN-alpha) in response to a virus stimulus. It was found that cells both adherent and nonadherent to plastic formed IFN-alpha after induction by any one of several viruses studied. When nonadherent cells were separated on discontinuous Percoll gradients, only the cells in the less dense Percoll fractions produced IFN, whatever the virus used. By indirect immunofluorescence with monoclonal antibodies to HLA-DR and to Leu 11b, the distribution of the HLA-DR+ cells was shown to resemble most closely that of the IFN-producing population. Elimination of these cells (by complement-mediated lysis with the same antibodies) abrogated the IFN response, but NK cells remained and thus do not produce IFN-alpha. In confirmation, elimination of the Leu 11b+ cells had no effect on the amount of IFN produced. PBMC preparations from patients with chronic lymphocytic leukemia (CLL) appeared incapable of producing IFN-alpha but were shown to contain identifiable IFN-producing cells. The low or absent IFN levels in CLL are probably due to the relative scarcity of IFN-producing cells in their PBMC.

Antigens, Surface↗
PubMed1985

The effect of indomethacin on the activation and effector function of suppressor cells from tumor-bearing mice.

The spleens of mice with large M-1 fibrosarcomas contain two populations of suppressor cells with the properties of macrophages and T cells. In this study, we tested the effect of indomethacin on suppressor cell activation and effector function. Neither the activation nor the effector function of the suppressor macrophages was inhibited by indomethacin, and the activity of suppressor macrophages correlated with the tumor size. In contrast, the treatment of tumor-bearing mice with indomethacin from the day of injection of tumor cells completely blocked the in vivo activation of suppressor T cells. Indomethacin did not, however, depress suppressor T cell activity if mice were treated only during the third week of tumor growth. The effector function of the suppressor T cells, as assessed in mixing assays, was partially blocked by indomethacin, while selective suppression by low-molecular-weight factors was completely blocked if indomethacin was present in the cultures. Furthermore, the in vitro activation of suppressor cells by soluble factors secreted by tumor-bearer spleen cells was completely blocked by indomethacin, and this inhibition was reversed by prostaglandin E1. These data are consistent with the hypothesis that prostaglandins are involved in the activation, but not the effector function, of tumor-activated suppressor T cells.

Animals↗
PubMed1985

Activation of suppressor T cells by low-molecular-weight factors secreted by spleen cells from tumor-bearing mice.

The spleens of mice bearing large M-1 fibrosarcomas have been shown to contain several populations of cells which nonspecifically suppress antibody synthesis by cocultured normal spleen cells. It has now been shown that the spleens of tumor-bearing mice also contain inducer cells which secrete soluble factors capable of activating suppressor T cells from unprimed precursor cells. The activated suppressor cells are Thy 1+, Lyt 1+2+ and secrete a soluble suppressive factor. They inhibit the in vitro generation of antibody-forming cells by cocultured normal spleen cells stimulated by T-cell-dependent antigens. They do not, however, suppress the antibody response to T-cell-independent antigens and do not inhibit antibody synthesis by cocultured nude mouse spleen cells cultured with T-cell-dependent antigens and exogenous helper factors. In addition, suppression is blocked if conditioned medium containing T-cell growth factors is added to the suppressor cell assays. These data suggest that cells in the spleens of tumor-bearing mice secrete inducing factors which activate suppressor cells. These activated suppressor cells in turn secrete soluble suppressor factors which inhibit antibody synthesis, possibly by interfering with the synthesis or release of T-cell growth factors.

Animals↗
PubMed1985

Induction of suppression by a murine nonspecific suppressor-inducer cell line (M1-A5).

A murine nonspecific suppressor-inducer cell line (M1-A5) was established by the limiting dilution method from the spleen cells of a mouse bearing an advanced methylcholanthrene-induced fibrosarcoma. Indirect immunofluorescence studies demonstrated that the M1-A5 cells were Thy-1-, sIg-, Ly-5+, MAC-, and 45% asialo GM1+. The M1-A5 cells were able to activate suppressor cells from unprimed, syngeneic normal spleen cells. These activated cells inhibited antibody production by cocultured syngeneic lymphoid cells. Induction of suppression by the M1-A5 cells was via the release of a suppressor-inducing factor, which was found to be protein in nature. Kinetic studies showed that when M1-A5 cells were separated from NSC by a dialysis tubing in Marbrook vessels, the M1-A5 cells required a minimum of 8 hr incubation period before suppressor cell activity could be demonstrated in precursor cells. On the other hand, induction of suppression by the suppressor-inducing factor required a minimum of 3 hr exposure of the precursor cells to the factor.

Animals↗
PubMed1981

Non-specific cytotoxic cells generated in vitro in response to a weakly immunogenic murine adenocarcinoma. In vivo correlations.

Tumor 85 adenocarcinoma cells, which are very weakly immunogenic for C3H/HeN (C3H) mice, provide a model tumor system for studying the parameters of induction of a cell-mediated immune response which does not appear to be a traditional cytotoxic T-cell or NK-cell response. Mice pre-immunized with irradiated tumor 85 cells are protected about 50% of the time from a challenge of viable tumor 85 cells although it is never possible to protect 100% of the immunized mice. Optimal protection is observed in mice immunized with 10(6) irradiated tumor 85 cells 14 days prior to challenge. Protection is also observed if mice are immunized with Protection is also observed if mice are immunized with 3H or C3HfeB/HeN (C3Hf) tumors originally induced by the same carcinogen as that used to induce tumor 85. The injection of carrageenan 1 h before challenge completely reverses the protection observed in immunized mice and and tumors grow faster in carrageenan-treated immunized mice than in normal mice. Two populations of cells obtained from cultures of spleen cells stimulated by tumor 85 cells appear to prevent tumor growth in vivo. One population, which is cytotoxic for tumor 85 cells in vitro, is nylon-wool-adherent and expresses Thy 1.2. The second population, which is not observed to be cytotoxic in a 51Cr release assay, is phagocytic.

Adenocarcinoma↗
PubMed1981

An assay for virus-specific help for B cells.

Spleen cells from mice immunized with vaccinia or influenza viruses were mixed with spleen cells from mice immunized by dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH) and transferred into irradiated syngeneic recipient mice which were subsequently restimulated with trinitrophyenylates (TNP) or unmodified viruses. One week later, spleens were removed and assayed for indirect anti-DNP plaque-forming cells (PFC). When spleen cells from both influenza and vaccinia primed mice were restimulated with the haptenated form of the virus used for the initial immunization there was an enhanced PFC response compared to that seen with spleen cells from unprimed mice.

Animals↗