Inhibition of in vitro antibody synthesis by cyclophosphamide-induced suppressor cells

Nitric oxide-producing CD11b+Ly-6G(Gr-1)+CD31(ER-MP12)+cells in the spleen of cyclophosphamide–treated mice: implications for T-cell responses in immunosuppressed mice

During recovery from intensive chemotherapy with cyclophosphamide (CTX), mice suffer a severe but transitory impairment in spleen cell proliferation to T-cell mitogens (Con A or anti-CD3 plus IL-2). Although CTX treatment reduced spleen T-cell cellularity, this cannot fully account for T-cell unresponsiveness. The results showed that CTX induces the colonization of spleen by an immature myeloid CD11b+Ly-6G+CD31+ population. Its presence closely correlated with the maximum inhibition of T-cell proliferation. Moreover, this suppressive activity was dependent on nitric oxide (NO) production in cultures since (1) higher amounts of nitric oxide and inducible nitric oxide synthase (iNOS) mRNA were produced in CTX spleen cells (CTX-SC) than in control splenocyte cultures and (2) NOS inhibitors greatly improved the proliferation of T lymphocytes. Nitric oxide production and suppressive activity were also dependent on endogenous interferon-γ (IFN-γ) production since anti–IFN-γ abrogated both effects. Finally, iNOS protein expression was restricted to a heterogeneous population of CD31+cells in which CD11b+Ly-6G+ cells were required to suppress T-cell proliferation. These results indicated that CTX might also cause immunosuppression by a mechanism involving the presence of immature myeloid cells with suppressor activity. This may have implications in clinical praxis since inappropriate immunotherapies in patients treated with intensive chemotherapy could lead to deleterious T-cell responses. (Blood. 2000;95:212-220)

Nitric oxide-producing CD11b+Ly-6G(Gr-1)+CD31(ER-MP12)+cells in the spleen of cyclophosphamide–treated mice: implications for T-cell responses in immunosuppressed mice

During recovery from intensive chemotherapy with cyclophosphamide (CTX), mice suffer a severe but transitory impairment in spleen cell proliferation to T-cell mitogens (Con A or anti-CD3 plus IL-2). Although CTX treatment reduced spleen T-cell cellularity, this cannot fully account for T-cell unresponsiveness. The results showed that CTX induces the colonization of spleen by an immature myeloid CD11b+Ly-6G+CD31+ population. Its presence closely correlated with the maximum inhibition of T-cell proliferation. Moreover, this suppressive activity was dependent on nitric oxide (NO) production in cultures since (1) higher amounts of nitric oxide and inducible nitric oxide synthase (iNOS) mRNA were produced in CTX spleen cells (CTX-SC) than in control splenocyte cultures and (2) NOS inhibitors greatly improved the proliferation of T lymphocytes. Nitric oxide production and suppressive activity were also dependent on endogenous interferon-γ (IFN-γ) production since anti–IFN-γ abrogated both effects. Finally, iNOS protein expression was restricted to a heterogeneous population of CD31+cells in which CD11b+Ly-6G+ cells were required to suppress T-cell proliferation. These results indicated that CTX might also cause immunosuppression by a mechanism involving the presence of immature myeloid cells with suppressor activity. This may have implications in clinical praxis since inappropriate immunotherapies in patients treated with intensive chemotherapy could lead to deleterious T-cell responses. (Blood. 2000;95:212-220)

Immunoregulatory potential of exogenous Schistosoma mansoni soluble egg antigen in a model of experimental schistosomiasis--I. Regulation of granuloma formation in vivo

This study was undertaken to assess the optimum conditions required to reduce the vigorous host granulomatous reaction around Schistosoma mansoni eggs. Soluble schistosomal egg antigen (SEA) at a concentration of 10 or 100 micrograms protein was administered i.p. or i.v. into unprimed C57BL/6 mice. SEA was injected either alone or in combination with cyclophosphamide (CY) 100 or 50 mg/kg via i.p. route. Seven or 14 days later viable eggs of S. mansoni were injected via the tail vein into treated groups and untreated normal controls. Mice were sacrificed 8, 16 and 24 days after the injection of eggs. The lungs were removed for histopathological study, measurement of granuloma diameter and phenotypic analysis of granuloma intralesional T-cell subsets. Compared to untreated controls, the lower concentration of SEA (10 micrograms) administered by the i.v. route 7 days before egg injection, induced a significant reduction in granuloma diameter 16 days after egg injection than that by the i.p. route or at a higher SEA concentration (100 micrograms). Compared to untreated controls, the higher dose of CY (100 mg/kg), given i.p. alone or in combination with 10 micrograms SEA by the i.v. or i.p. route, induced a significant reduction in granuloma diameter, while 50 mg/kg CY did not cause any reduction. The reduction in granuloma diameter by i.v. administration of low SEA concentration alone or in combination with CY IP, was associated with a decrease in the granuloma intralesional L3T4+/Lyt2+ ratio. The decrease in the ratio was due to an increase in Lyt2+ cells. The results suggest that the use of low dose SEA by the i.v. route alone or combined with an immunosuppressive drug ameliorates pathological changes concurrent with S. mansoni infection.

Impairment of T-helper function by a Plasmodium berghei-derived immunosuppressive factor

Mice injected with an immunosuppressive factor (ISF) extracted from Plasmodium berghei-infected rat erythrocytes have a reduced antibody response to unrelated antigens. T-cells from ISF-treated mice failed to provide adequate help to naive, syngeneic B-cells in the primary IgM response in vitro to sheep red blood cells and to dinitrophenylated keyhole limpet hemocyanin. The same T-cells, however, were able to cooperate with memory B-cells in the secondary IgG response. No other cellular deficit was detected in ISF-treated mice; B-cells and macrophages behaved normally, and there was no detectable excess of suppressor cells. The T-cell impairment was not reflected in decreased production of interleukin 2, but was also shown by the diminished delayed type hypersensitivity reaction to sheep red blood cells of ISF-treated mice.

The effect of single dose, intravenous cyclophosphamide on the mouse intestinal IgA response to cholera toxin

The IgA response of gut associated lymphoid tissue (GALT) to enteric pathogens is a vital component of the mucosal barrier. This study describes the effect of cyclophosphamide (Cy) on the IgA anti-CT response of Peyer's patch (PP) and lamina propria cells derived from mice previously challenged enterically with two weekly doses of 10 micrograms CT. Under normal circumstances, both PP and lamina propria responses peaked 7 days after the second dose of CT. To evaluate the effect of a single dose of Cy on this response, mice were given Cy (50 mg/kg) intravenously on days -2, 0, 2 or 7 relative to the initial dose of CT. Cultures of PP and jejunal segments were established 7 days after the booster dose of CT (time or normal peak response). A single dose of Cy suppressed the IgA anti-CT response of PP and, to a lesser extent, jejunal segment cultures only if the drug was given 2 days before the primary dose of CT. This suppression of the anti-CT response was overcome when Cy was given 2 days before CT priming, and CT was administered three times, on days 0, 7 and 14; thus, the effect of Cy was brief and did not appear to promote tolerance to CT. These data show that a single, moderate dose of Cy, given before enteric priming of the GALT, can inhibit the mucosal IgA response to CT. The effect of Cy is relatively brief and dependent upon the time at which the drug is given relative to the induction of the mucosal immune response.

Cyclophosphamide-induced suppressor cells in mice: suppression of the antibody response in vitro and characterization of the effector cells

It was found earlier that nonspecific suppressor cells obtained from the spleen of mice injected with cyclophosphamide (Cy) at a dose of 200 mg/kg body wt are nonadherent, surface Ig negative, and Thy-1 negative. It is now reported that Cy-induced suppressor (Cy-S) cells suppress the in vitro primary and secondary humoral responses in a dose-dependent manner. Suppressor activity is a property of a low density cell that is found in the spleen from 5 to 11 days after Cy administration. Cy-S cells are negative for a number of T-cell markers and are nonadherent to plastic. They are not agglutinated by peanut agglutinin and do not acquire the Thy-1 antigen after treatment with thymosin, suggesting that they are not T-cell precursors. While NK activity was detected in the Cy-S cell preparations, this activity was removed by treatment with antibodies specific for the Qa-5 antigen and complement without affecting the suppressor activity. Cy-S cells are, therefore, distinct from B cells, T cells, NK cells, and macrophages.

Opposite effects of cyclophosphamide pretreatment on tuberculin hypersensitivity during the course of sensitization of mice with Mycobacterium bovis BCG

The influence of cyclophosphamide (CY) pretreatment upon the development of tuberculin hypersensitivity has been studied during the course of infection of mice with BCG. An enhancement of the DTH response to BCG antigens occurred during the induction phase, whereas a depression of this response occurred at the peak and during the decay phase of sensitization. The development of the early DTH-promoting and of the late DTH-depressing effect of CY was favoured by the use of a supra-optimal dose of BCG. Both these effects were cell-dependent since they could be transferred adoptively to syngeneic recipient mice with sensitized lymphoid cells but not with specific immune sera. Pretreatment with CY favoured the emergence of cells capable of responding in vitro to BCG antigens in the draining lymph nodes of BCG-infected mice. No simple association however, exists between this in vitro lymphocyte transformation response and the DTH response.

Specific suppression of humoral and delayed hypersensitivity responses by cyclophosphamide in an experimental model of autoimmunity

The aim of this report is to investigate the effect of cyclophosphamide (CY) in an experimental model of autoimmunity to rat male accessory glands. The results indicated that 100 mg/kg of this drug suppressed humoral immune response that persisted for at least 45 days when administered 3 days after the first immunization of rats with modified rat male accessory glands (MRAG) in complete Freund's adjuvant (CFA). Administration of the drug 3 days before ID injection of antigen caused a shorter suppression of antibody formation. Delayed type hypersensitivity (DTH) studied 13 days after the first immunization was suppressed only in the animals that were administered CY after the antigen. The specificity of the immunosuppression was studied in rats treated with CY after the first immunization with MRAG using aggregated human gamma-globulin (AHGG) as an unrelated antigen. The studies demonstrated significant suppression of DTH (p less than 0.005) and humoral immunity only against MRAG. On the contrary, the response to AHGG was not significantly modified.

Evaluation of the immunosuppression in an experimental model of autoimmunity: suppressor activity of spleen cells from cyclophosphamide-treated rats

Rats immunized with chemically modified rat male accessory glands (MRAG) and injected 3 days later with cyclophosphamide (CY) were unable to develop humoral and cellular immune response to the autoantigen of MRAG. The present report demonstrates that the spleen mononuclear (SpM) cells transference from rats injected with CY 3 days after the antigen to normal male or female syngeneic animals before immunization with MRAG did not suppress the immune response to this antigen, whereas the transference of SpM cells from suppressed animals to animals previously immunized, depressed the delayed type hypersensitivity (DTH) response against MRAG (suppression of the expression) only in male rats. Similar results were obtained by transference of purified T cells. SpM cells did not suppress an established humoral immune response induced in male or female rats. The results suggest that non-adherent cells present in the spleen of male suppressed rats might be one of the responsible mechanisms for suppression of the efferent phase of the cellular autoimmune response to MRAG.

Effects of treatment with immunomodulatory drugs on thymus and spleen lymphocyte subpopulations and serum corticosterone levels

Immunofluorescence was used to characterize the lymphocyte subpopulations of mice treated with six immunomodulatory drugs: hydrocortisone acetate (HCA), corticosterone acetate (corticosterone), cyclophosphamide, cytosine arabinoside (Ara-C), 15(S)-methyl prostaglandin E1 (15(S)-methyl PGE1), and 2-amino-5-bromo-6-phenyl-4-(3H)-pyrimidinone (ABPP). The number of thymus and spleen cells bearing Thy-1, Ig, Lyt-1 and Lyt-2 antigens and the density of the antigens on each cell (IF profiles) were determined. Microscopic examination of cells stained with rhodamine-labeled anti-Lyt-2 and fluorescein-labeled anti-Lyt-1 was used to measure the proportion of Lyt-1+2-, Lyt-1+2+, and Lyt-1-2+ cells in the spleen and thymus of drug-treated animals. The changes in lymphocyte subpopulations were compared with the varied effects of these drugs on antibody formation and graft vs host (GVH) reaction. Three immunosuppressive drugs, HCA, cyclophosphamide, and Ara-C, depleted the thymus of cells expressing a large quantity of Thy-1. The drug-resistant cells were larger and had more Lyt-1 than cells from control animals. HCA treatment depleted the thymus of Lyt-1+2+ cells; the cortisone resistant cells were primarily Lyt-1+2-. Cyclophosphamide and the antiviral immunostimulant, ABPP, caused similar, but less marked, alterations. The proportion of Lyt-1-2+ cells in the thymus was reduced by treatment with all the drugs, but the density of Lyt-2 on the drug-resistant cells was not altered. Treatment with Ara-C or 15(S)-methyl PGE1 produced a very modest evaluation in Lyt-1+2- cells. 15(S)-Methyl PGE1, which suppresses some immuno-inflammatory reactions, had no discernible effect on thymocyte size or the IF profile of Thy-1, Lyt-1, or Lyt-2. In the spleen, the amount of Thy-1 and of immunoglobulin on cells bearing these markers was changed very little by drug treatment. The proportion of splenic B cells was diminished by treatment with cyclophosphamide and, to a lesser extent, by HCA, while the proportion of spleen cells bearing detectable Thy-1 and Lyt-1 increased correspondingly. The proportion of cells bearing Lyt-2 was altered by only two drugs; cyclophosphamide increased both Lyt-1+2+ and Lyt-1-2+ spleen cells and ABPP (an interferon inducer which stimulates antibody formation) decreased both Lyt-2+ subpopulations. Treatment with two drugs caused the serum corticosterone concentration to rise: ABPP increased serum corticosterone substantially while the prostaglandin induced a smaller and more transitory increase. An indirect mechanism, via corticosteroid release, might explain the thymic depletion observed in mice treated with 15(S)-methyl PGE1 and ABPP, but neither the suppression of the GVH reaction by these drugs nor polyclonal activation of B cells by ABPP can be attributed to endogenous corticosteroids. Our data show that enumeration of splenic lymphocyte subpopulations by immunofluorescence techniques may aid in elucidating the mode of action of immunomodulatory drugs.

Characterization of cyclophosphamide-induced suppressor cells

Spleen cells from mice injected with cyclophosphamide (200 mg/kg body weight) suppress the secondary immunoglobulin (IgG antibody response of memory cells to a T-dependent antigen, dinitrolphenylated (DNP) human gamma globulin, in Millipore diffusion chambers. Characterization of the suppressor cell revealed that it was nylon wool nonadherent, insensitive to treatment with anti-Thy 1.2 or anti-Ig serum plus C, found in spleen but not thymus or lymph nodes, generated in thymectomized mice and nude mice, and heat-sensitive. Because of these unique characteristics, it was concluded that the suppressor cell was not a typical B cell, T cell, or macrophage. The suppressor cell was found to be regulated, i.e., inhibited, by a T cell found in the thymus and possibly the lymph nodes of normal mice. The suppressor cells may have biological significance in relation to development of self-tolerance.

Immunoregulatory T cells in the peripheral blood of patients with Bechterew's syndrome

Seventeen patients with ankylosing spondylitis (Bechterew's syndrome) were investigated. Only 3 of them had detectable autoantibodies, but the IgA and IgM concentrations in serum were increased (p less than 0.05). The patients had a moderate reduction in con-A-induced suppressor cell activity of peripheral blood lymphocytes as detected in con-A/MLC assay, compared with that of 15 controls (41.0 +/- 8.6% suppression compared with 59.4 +/- 5.2%, mean +/-SEM; 0.05 less than p less than 0.1 one-sided test). No differences were found in the percentages of T gamma cells (suppressor cells) and T mu cells (helper cells) between patients an controls. This is to our knowledge the first report of con-A-induced suppressor cell activity an T lymphocyte subpopulations in the peripheral blood of patients with ankylosing spondylitis.