Macrophages and resistance to tumours: influence of agents affecting macrophages and delayed-type hypersensitivity on resistance to tumours inducing concomitant immunity.

Early, specific concomitant immunity to each of four tumours was inhibited by treatment with silica or carrageenan. Late, non-specific concomitant immunity was, with one exception, not inhibited by these agents. Treatment of non-immune mice with silica at certain critical periods before challenge promoted the growth of four of six syngeneic methylcholanthrene-induced tumours in their feet. Treatment with carrageenan was much less effective. Early and late concomitant immunity were inhibited by one or more agents inhibiting delayed-type hypersensitivity: irradiation, niridazole and reserpine. Irradiation of non-immune mice did not effect the growth of tumours in their feet. Treatment of non-immune mice with niridazole or reserpine actually inhibited the growth of some tumours. It is suggested that (a) mice offer some natural resistance to tumour growth, macrophages perhaps being effectors; (b) some tumour isografts may survive only if an inflammatory reaction occurs; (c) mechanisms akin to those of delayed-type hypersensitivity operate in the expression of concomitant immunity; (d) macrophages are important in early, specific concomitant immunity, but perhaps less so in the late non-specific phase.     

Effects of CKS-17, a synthetic retroviral envelope peptide,on cell-mediated immunity in vivo: Immunosuppression,immunogenicity, and relation to immunosuppressive tumor products

Summary CKS-17 is a heptadecapeptide corresponding to a region highly conserved in retroviral transmembrane proteins such as p15E. Because a relationship had previously been determined between p15E and immunosuppressive tumor cell products, we examined the effect of CKS-17, control peptides and conjugates thereof on the expression of cell-mediated immunity (delayed-type hypersensitivity, DTH) in mice. Conjugates of CKS-17 inhibited DTH reactions to sheep erythrocytes in the feet of mice. The degree of inhibition was dose-dependent. Unconjugated CKS-17 had almost no effect, and control peptide conjugates had no inhibitory effect. Immunization of mice with CKS-17 conjugates, but not with control conjugates, rendered them resistant to the depression of DTH reactions, not only by CKS-17 conjugates, but also by products of cultured tumor cells. CKS-17 conjugates, but not control conjugates, also depressed the cellular inflammatory reactions induced in mouse footpads by concanavalin A (ConA) and immunized mice against the depression of ConA reactions by products of cultured tumor cells. Injections of globulin from sera of mice immunized with CKS-17 conjugates conferred upon normal recipients resistance to the depression of footpad reactions to ConA by products of cultured tumor cells. Globulin from sera of normal mice or control immunized mice did not confer such resistance. Thus conjugates of a synthetic peptide not only mimic the immunosuppressive effects of tumor products in vivo, but can also immunize mice against those effects.     

The effect of locally injected vasoactive amines on the elicitation of delayed-type hypersensitivity.

In previous work monoamine depletion due to treatment with reserpine was shown to decrease the elicitabiltiy of DTH responses in mice. In addition, treatment with monoamine oxidase inhibitors prevented the reserpine-induced decrease. These findings led to the suggestion that serotonin-induced increased vascular permeability is necessary to the development of DTH reactions, perhaps by allowing bone marrow-derived macrophage precursor cells, which are obligate components of DTH responses, to migrate through specialized venules into the site of the reaction. We have compared classical drug tachyphlaxis (temporary inhibition of the effects of a drug by prior treatment with agonists) to serotonin in vessels of mouse feet with local inhibition of DTH after serotonin pretreatment of mice. During the tachyphylactic period, DTH responses are depressed. This suggests that serotonin-induced tachyphylaxis of local endothelial receptors can be responsible for DTH inhibition. In contrast, local injection of histamine has no effect on DTH and this drug is a much less potent inducer of tachyphylaxis to serotonin-mediated vasoactive reactions. On the other hand, histamine can inhibit in vitro T cell reactions, which are not affected by serotonin. These data help to further the concept that serotonin plays an important role in the regulation of DTH in mice and that it probably does so by acting on vascular endothelium.     

A role for mast cells and the vasoactive amine serotonin in T cell-dependent immunity to tumors

The involvement of mast cells in anti-tumor resistance was studied by employing 2 strains of mast cell deficient but otherwise immunocompetent mice on a C57BL/6 (H-2b) background (W/Wv and Sl/Sld) and their respective normal +/+ littermate controls. Sensitization of control mice with irradiated semisyngeneic B16 melanoma cells (H-2b) resulted in protection against subsequent challenge with viable B16 cells, in contrast to sensitization of either W/Wv or Sl/Sld mice. The involvement of serotonin in antitumor resistance was studied by employing 2 serotonin active drugs: reserpine, that depletes mast cells of serotonin; and methysergide, a serotonin antagonist. Sensitization of BDF1 mice with irradiated B16 cells and sensitization of DBA/2 mice (H-2d) with irradiated SL2 cells (H-2d) resulted in protection against subsequent challenge with viable B16 cells and viable SL2 cells, respectively. Treatment with either reserpine or methysergide resulted in a decreased protection. Delayed-type hypersensitivity (DTH) footpad responses to allogeneic L5178Y (H-2d) tumor cells in C57BL/6 mice showed a biphasic reaction pattern, similar to that found in DTH responses to simple reactive haptens, such as picryl chloride. Moreover, the early swelling responses were also dependent on T cells and on mast cells. BDF1 mice carrying a semisyngeneic L5178Y tumor on the chest showed an early swelling response after footpad challenge but no late response, possibly indicating that selective down regulation of the late component of DTH was associated with progressive tumor growth in these animals. The biphasic patterns of DTH to both tumor cells and picryl chloride and the T cell and mast cell dependence of both antitumor resistance and DTH to tumor cells suggest that T cell-dependent activation of mast cells to allow entry of mononuclear leukocytes into sites of tumor growth is similar to the mechanism that occurs in DTH.     

Depression of macrophage functions and T-cell-mediated immunity to listeria infection in tumor-bearing mice and its prevention by PSK

Summary The effect of PSK on the depressed bactericidal activity of macrophages and delayed-type hypersensitivity (DTH) to Listeria monocytogenes in BALB/c mice bearing transplantable Meth A fibrosarcoma was studied. In tumor-bearing mice pretreated with PSK, L. monocytogenes was cleared rapidly from the circulating blood and bacterial growth in the liver was inhibited effectively in the early phase of infection. This resistance to the infection could be transferred with adherent peritoneal exudate cells (PEC) but not with nonadherent or adherent spleen cells of PSK-treated mice. In the early phase of infection, tumor-bearing mice developed a lower level of DTH to L. monocytogenes than nongrafted control mice. However, the control levels of DTH could be obtained by pretreatment with PSK in tumor-bearing mice. These results suggest that the restoration of DTH to L. monocytogenes by pretreatment with PSK may be attributable to the restoration of the depressed immunological responsiveness to the normal levels in tumor-bearing mice.     

Some characteristics of the in vivo antitumor immunity exhibited by mice cured of a large MOPC-315 tumor by a low dose of melphalan

Summary BALB/c mice cured of a large MOPC-315 or MOPC-104E plasmacytoma following treatment with a low dose (2.5 mg/kg) of melphalan (L-PAM) were resistant to challenge with the other plasmacytoma but to a much lesser extent than to challenge with the autochthonous plasmacytoma. The resistance of the L-PAM-cured MOPC-315-tumor bearers to challenge with MOPC-104E tumor cells was increased when the MOPC-104E tumor cells were admixed with MOPC-315 tumor cells prior to their inoculation. This enhanced resistance to MOPC-104E cells was due to elimination of the MOPC-104E tumor cells through an innocent bystander killing effect since it did not render the mice more resistant to a subsequent challenge with MOPC-104E tumor cells alone. Administration of carrageenan to L-PAM-cured MOPC-315-tumor bearers 1 day after the challenge with the mixture of MOPC-104E and MOPC-315 tumor cells drastically reduced the ability of the mice to resist the tumor challenge. All of the tumors that developed in such mice were of MOPC-104E origin only (as judged by the binding specificity of the myeloma proteins secreted by the tumor cells as well as that present on their surface) even though (a) the tumor inoculum used consisted of up to 10-fold more MOPC-315 than MOPC-104E tumor cells and (b) the MOPC-315 tumor cells divide more rapidly. The same protocol of carrageenan treatment did not reduce the ability of normal BALB/c mice to develop in vivo a primary cell-mediated cytotoxic response nor a primary antibody response indicating that it has no effect on the initiation of an immune response. Therefore, it is conceivable that carrageenan treatment reduced the ability of L-PAM-cured MOPC-315-tumor bearers to reject a challenge with MOPC-315 and MOPC-104E tumor cells by interfering at the effector stage. The ability of the L-PAM-cured MOPC-315-tumor bearers to reject the MOPC-315 cells present in the challenge mixture was reduced when the mice were treated with anti-Thy 1.2 antibody but not with carrageenan, indicating that T-cells independent from carrageenansensitive effector cells are required for the rejection of the MOPC-315 tumor cells. Thus, at least two different effector mechanisms participate in the rejection of a challenge composed of MOPC-315 and MOPC-104E tumor cells by L-PAM-cured MOPC-315-tumor bearers. One of the mechanisms is dependent on the action of carrageenansensitive effector cells while the other does not require carrageenan-sensitive effector cells but is T-cell-dependent.Supported by Research Grant IM-435 from the American Cancer Society and Research Grant CA-35761 from the National Cancer InstituteIn partial fulfillment of the requirements for the Doctor of Philosophy degree     

Study of the immunosuppressive effect of cyclosporine in experimental studies]

Specific immunosuppressive activity of cyclosporine prepared at the National Research Centre of Antibiotics by using its original producing culture was studied. It inhibited basic cellular immune responses such as DTH and transplant vs. host and prolonged the lifespan of tumor xenografts under the kidney capsule. Cyclosporine also suppressed the humoral immunity. Its inhibitory effect on lymphocyte blast transformation induced by lectins and in mixed lymphocyte cultures was shown in vitro. Cyclosporine inhibited activity of natural killer cells and T-suppressor cells induced by concanavalin A. It was demonstrated on the models of skin allotransplantation in mice and heterotopic transplantation of the heart in rats that cyclosporine prolonged the transplant lifespan. By the main indices of the cellular immunity and in the models of the transplantation immunity, cyclosporine prepared at the National Research Centre of Antibiotics was shown to be similar to that manufactured by Sandoz.     

Augmentation of antitumor resistance by a strain of unicellular green algae,Chlorella vulgaris

Summary Growth of Meth-A tumor in CDF1 mice was inhibited significantly by injection of a hot water extract of a strain of Chlorella vulgaris (CE) into the tumor or into the subcutaneous tissue near the tumor. The augmentation of resistance by CE may require the participation of T cells and macrophages, since it was abolished or reduced in athymic nude mice or mice treated with carrageenan, a macrophage blocker. Mice treated with CE exhibited antigen-specific augmented resistance against rechallenge with tumor. Moreover, the antitumor effect of CE was comparable with that of Corynebacterium parvum, but its mechanism of effect might be different.     

Augmentation of delayed-type hypersensitivity and resistance against allogeneic or syngeneic methylcholanthrene-induced tumors in mice preimmunized with the tumor extracts

Delayed-type hypersensitivity (DTH) responses against methylcholanthrene-induced fibrosarcomas in C3H/He and BDF1 mice were developed in BDF1 mice by sc injection of the respective mitomycin C-treated tumor cells. The DTH responses to the allogeneic and the syngeneic tumor cells were accelerated and enhanced tumor-specifically by priming 7 days previously with KCl extracts of the respective tumors. The ability in the mice primed with the tumor extracts enhancing the DTH response against the tumor cells could be transferred to recipient mice by the spleen cells, but not by the T-cell-depleted spleen cells. Rejection of allogeneic tumor was accelerated under the development of accelerated and enhanced DTH response against the allogeneic tumor antigens. Moreover, resistance to syngeneic tumor growth increased significantly with the development of accelerated and enhanced DTH response against the syngeneic tumor antigens. Thus, the augmentation of DTH response by preimmunization with tumor extracts was accompanied by the increased resistance to tumor growth, suggesting that T cells involved in the augmentation of tumor-specific DTH response play some role in increasing the resistance to tumor growth.     

Suppression of delayed-type hypersensitivity to oxazolone in whole-body-irradiated mice and protection by WR-2721

The effect of whole-body irradiation on cellular immunity, as measured in vivo by delayed-type hypersensitivity (DTH) to oxazolone (4- ethoxymethylene -2-phenyl- oxazol -5-one), was determined in CD2F1 mice. DTH, determined by changes in ear swelling after challenge with oxazolone, was significantly depressed in irradiated mice (500-900 rad of 60Co) in a dose-dependent fashion when animals were irradiated after sensitization and before challenge with oxazolone. Administration of WR-2721 [S-2-(3-aminopropylamino)ethylphosphorothioic acid] 30 min before irradiation (2 days after sensitization) resulted in protection against suppression of DTH, which was dependent on drug and radiation dose. An effective dose of WR-2721 (200 mg/kg body wt) provided an approximate dose-modifying factor of 1.3. The data suggest that WR-2721 interacts with cells involved in that DTH response (lymphocytes and/or macrophages) and that WR-2721 may be useful in protecting against radiation-induced decrements in cell-mediated immunity.     

Natural immunity to grafts of FLD-3 erythroleukemia cells by irradiated mice

Mice were irradiated and infused with BALB/c Friend virus-induced FLD-3 erythroleukemia cells. Growth of the cells was estimated by measuring splenic incorporation of 5-iodo-2'-deoxyuridine-125I 5 days after cell transfer. BALB/cJ and C3H mice were 'poor responders' in that FLD-3 cells grew well in their spleens, while mice of other strains were 'good responders', resisting the growth of FLD-3 cells. No H-2 or Fv genetic locus was associated with resistance. Athymic nude mice and mice depleted of marrow tissue by 89Sr or estradiol resisted FLD-3 cells, indicating that the effectors were thymus- and marrow-independent. Silica, carrageenan and Propionibacterium acnes organisms all altered resistance, suggesting a function of macrophages. Neither interferon nor anti-interferon serum treatment altered resistance. Anti-asialo GM1 serum inhibited resistance to FLD-3 cells in vivo and inhibited natural cytotoxic (NC) activity against FLD-3 cells in vitro. NC (FLD-3) activity was greatly decreased in spleens 3 days after irradiation, in contrast with NK (YAC-1) and NC(WEHI-164.1) activities. Moreover, a 3-day delay in infusion of FLD-3 cells 'synergized' with silica in weakening genetic resistance in vivo. Thus, natural immunity to FLD-3 cells in vivo differs from that of genetic resistance to normal bone marrow cell allografts, and the lysis of FLD-3 cells in vitro seems to be mediated by cells which do not easily fit into the definition of natural killer (NK) or natural cytotoxic (NC) cells.     

Cutaneous leishmaniasis in anti-IgM-treated mice: enhanced resistance due to functional depletion of a B cell-dependent T cell involved in the suppressor pathway

The contribution of B cells and antibodies to either the resistance or susceptibility to cutaneous leishmaniasis has been investigated in mouse strains rendered B cell-deficient by treatment with anti-mouse IgM antisera from birth (mu-suppressed). These studies confirm that immunity to cutaneous disease in a normally resistant mouse strain (C3H/HeJ) is independent of antibody, but that B cells and/or antibodies are required for the evolution of suppressed DTH and the consequent disease susceptibility of BALB/c mice. Anti-IgM-treated BALB/c mice, which lacked detectable anti-leishmanial antibodies during the course of infection, displayed a sustained DTH response to leishmanial antigen and were able to control their cutaneous lesions. The enhanced resistance of mu-suppressed mice could be completely abrogated by transfer of suppressor T cells from infected control animals into mu-suppressed mice before their infection. Thus the suppressor T cells, which are generated during leishmanial infection in BALB/c mice, can effect suppression in the absence of antibody. Evidence that B cells or antibodies are required for the generation of suppressor T cells was demonstrated by using BALB/c mice in which suppressor T cells fail to be generated during infection as a result of prior sublethal irradiation. Splenic T cells from normal mice could overcome the resistance conferred by sublethal irradiation, whereas splenic T cells from mu-suppressed mice could not. Thus the enhanced resistance of mu-suppressed BALB/c mice appears to be a consequence of their lack of functional expression of a B cell-dependent T cell critical to the suppressor pathway.     

Delayed-type hypersensitivity (DTH) in BCG-sensitized mice I. Lack of suppressor T cell activity on DTH to sheep red blood cells.

Mice pretreated with an intravenous (i.v.) injection of BCG (BCG-sensitized mice) and then immunized intravenously with a high dose (10(8)--10(9)) of sheep red blood cells (SRBC) 2 weeks later developed strong delayed-type hypersensitivity (DTH) to SRBC, as in mice pretreated with cyclophosphamide (CY) (CY-treated mice) and then immunized with SRBC 2 days later; normal mice given the same dose of SRBC did not show such DTH. The mechanism of this strong DTH to SRBC which developed in BCG-sensitized mice was studied, by comparing it with that in CY-treated mice. The transfer of either whole spleen cells or thymus cells, but not serum, obtained from mice immunized with i.v. injections of 10(9) SRBC 4 days previously (hyperimmune mice) did not suppress either the induction or the expression of DTH to SRBC in BCG-sensitized mice, but suppressed those in CY-treated mice. The suppressor cells were SRBC-specific T cells. Adoptive transfer of DTH to SRBC by spleen cells from either BCG-sensitized mice of CY-treated mice to hyperimmune recipients failed. The adoptive transfer of DTH from BCG-sensitized mice to normal recipients also failed if the spleen cells from hyperimmune mice were cotransferred. Whole body irradiation (600 rad) of mice 2 hr before or after the time of immunization with SRBC reduced significantly DTH to SRBC in both BCG-sensitized and CY-treated mice. It was noticed that the total number of spleen cells in BCG-sensitized mice was 3--4 times larger than that in CY-treated mice. From these results, we conclude that the entity of effector T cells of DTH to SRBC induced in BCG-sensitized mice and in CY-treated mice was not different in terms of susceptibility to suppressor T cells and irradiation, but that the total numbers of effector T cells generated in these mice differed remarkably, resulting in the above-described different responsiveness to suppressor T cells transferred passively.     

Regulation of anti-hapten antibody response by chemically modified carrier antigen preferentially provoking delayed-type hypersensitivity (DTH). II. DTH-reactivity and carrier-specific suppression of anti-DNP antibody response induced by priming with dodecanoyl-BSA are mediated by functionally distinct T cell subpopulations.

Experiments were carried out to determine whether or not the cell populations involved in DTH and in the suppression of antibody response are identical. The effects of four treatments, i.e., adult thymectomy (ATx), X-irradiation, anti-mouse thymocyte serum (ATS) and hydrocortisone (HC) on the induction of DTH and on the carrier-specific suppression of antibody response were observed in mice immunized with chemically modified antigen, dodecanoyl-BSA (d-BSA), emulsified with complete Freund's adjuvant (CFA), with the following results: 1) DTH induced by immunization with D -BSA remained constant in adult thymectomized mice, whereas the suppression of antibody response was not inducible in these animals. 2) Injection of low doses of ATS caused the depression of DTH in mice primed with D -BSA, but did not affect the suppressive activities of their spleen cells. 3) Sublethal X-irradiation 1 week prior to D -BSA priming inhibited the generation of suppressor cells but did not affect the generation of cells mediating DTH. The suppressive effect was also abrogated by sublethal X-irradiation given 2 days after immunization with DNP-BSA (14 days after priming with D -BSA). 4) The treatment of animals with HC 2 days before the footpad challenge or immunization with DNP-BSA depressed the ability of animals to induce both DTH and the suppression of antibody response. However, the latter was more sensitive to HC than the former. In addition to these results, it was also found that D -BSA-primed spleen cells were capable of suppressing anti-DNP response, but not of inducing DTH-reactivity upon transfer to recipient mice. These results suggest that DTH-reactivity and the carrier-specific suppression of anti-hapten antibody response induced by injection of D -BSA are mediated by different cell populations.     

Regulation of immune responses by T suppressor cells and by serum in chronic paracoccidioidomycosis

Regulation of cellular responses was studied during the course of chronic murine disseminated paracoccidioidomycosis. Regulation of peripheral blood lymphocyte (PBL) proliferative responses to concanavalin A (Con A) was studied in vitro by mixing PBL from infected and noninfected mice. PBL from mice infected for 18 weeks had depressed responses to Con A and they depressed the Con A responses of PBL from noninfected mice by 95% when they were mixed in a 1:1 ratio. After treatment of PBL from infected mice with anti-Lyt-2.2 antibody plus complement, the responses to Con A were increased to normal values. The percentage of T-cell subpopulations in PBL from infected mice did not differ significantly from those of normal mice. Immunoregulation of delayed-type hypersensitivity (DTH) responses to antigen by serum from infected animals was studied in mice 1 week after intranasal (i.n.) infection, a time when DTH responses were maximal. DTH responses to antigen 7 days after i.n. infection (10(7) CFU Paracoccidioides brasiliensis) were significantly reduced when 0.5 ml of immune mouse serum (ELISA antibody titer to P. brasiliensis antigens 1:10,240) was given i.v. 1 day before infection (P less than 0.01) or 1 day before skin testing (P less than 0.001). Normal mouse serum did not have this effect. The results indicate that progression of chronic disseminated paracoccidioidomycosis was associated with the development of T-cell suppressor activity for Con A responses of PBL, and that DTH responses to antigen were depressed by the administration of serum with specific high titer antibodies.     

Adoptive immunotherapy of a BALB/c lymphoma by syngeneic anti-DBA/2 immune lymphoid cells: Characterization of the effector population and evidence for the role of the host's non-T cells

Summary It has been previously shown that the BALB/c lymphoma YC8 is susceptible to lysis by syngeneic anti-DBA/2 lymphocytes and that YC8-bearing BALB/c mice can be cured by adoptive transfer of such immune effectors. In this study in vivo and in vitro functions of the curative immune lymphocytes have been evaluated together with the role of the host immune system in the mechanism of tumor eradication. It was found that the curative anti-DBA/2 lymphocytes were not directly cytotoxic to YC8 cells although they developed into YC8-lytic cells after in vitro restimulation with YC8. In vivo, the immune lymphocytes were able to mediate a tumor-specific delayed type hypersensitivity reaction against YC8 but had a low tumor-neutralizing activity in the Winn assay. Proliferation of infused BALB/c anti-DBA/2 lymphocytes was necessary for the in vivo therapeutic effect, since irradiation of effector cells or treatment of the donor immune lymphocytes with vinblastine abolished their curative capacity. Immunodepression of the T cell compartment of the prospective tumor-bearing animals by thymectomy plus irradiation or its abrogation in B mice (thymectomized, lethally irradiated, and reconstituted with fetal liver cells) did not interfere with the therapeutic effect of the transferred anti-DBA/2 lymphocytes. Blocking the macrophage functions of the host by carrageenan, however, abolished the therapeutic effect of immune lymphocytes. These data indicate that a radiation-resistant, non-T cell is involved in the tumor eradication induced by anti-DBA/2 lymphocytes. It was also shown that cured mice, tested 90 days after therapy, become resistant to 5×10³ LD₈₀ YC8 cells and that this resistance was due to the presence of memory cells derived from the transferred and not from the host lymphocyte population.     

A new interpretation of the involvement of serotonin in delayed-type hypersensitivity. Serotonin-2 receptor antagonists inhibit contact sensitivity by an effect on T cells

5-HT is a neuromediator and a vasoactive amine released by platelets and murine mast cells at sites of inflammation. A role for 5-HT has been proposed in murine DTH and has been attributed to its 5-HT2R-dependent vasoactive properties. We have tested the hypothesis that the role of 5-HT in DTH is related to an interaction of 5-HT with DTH effector T cells. In vivo treatment of sensitized mice with the 5-HT2R antagonists methysergide or ketanserin inhibited both their capacity to elicit DTH and the ability of their lymphoid cells to transfer DTH. In vitro treatment of lymphoid cells, or of nylon wool-purified T cells from sensitized mice, with 10(-7) to 10(-9) M of the 5-HT2R antagonists methysergide, ketanserin, ritanserin, or LY 53857, followed by three washings, inhibited as strongly their ability to transfer DTH, both systemically or locally. Systemic and local co-transfer experiments of 5-HT2R antagonist-treated and untreated cells indicated that this inhibition was not related to the induction of suppression. 5-HT2R antagonist treatment was nontoxic to T cells; did not affect the in vitro response of T cells to mitogen; selectively inhibited the efferent, but not the afferent limb of DTH; and in the efferent T cell cascade, affected the late-acting (24 h) inflammatory DTH T cells, but not the early-acting, DTH-initiating T cells. 5-HT2R selectivity was suggested by the absence of effect of an alpha-adrenergic R antagonist, and by prevention of the inhibitory effect of a 5-HT2R antagonist by prior incubation with the selective 5-HT2R agonist 1-(2,5-dimethoxy phenyl-4-methyl)-2 aminopropane. In summary, inhibition of DTH effector T cell function appeared sufficient, independently of any vascular effect, to account for the in vivo inhibitory effect of 5-HT2R antagonists on the elicitation of DTH. Our data suggest that late-acting DTH effector T cells might express functional 5-HT2R, and that these receptors might require in vivo activation in order for the T cells to locally produce the inflammatory lymphokine-dependent aspects of DTH.     

Niridazole, a potent long-acting suppressant of cellular hypersensitivity. III. Minimal suppression of antibody responses.

Niridazole, an anthelminthic drug, has been shown to be a potent long-acting suppressant of cell-mediated immune responses both in man and in experimental animals. In the present study the effect of niridazole on the magnitude and kinetics of the primary and secondary antibody responses of mice to sheep erythrocytes, human serum albumin, and keyhold limpet hemocyanin was investigated. The therapeutic dose of niridazole for murine schistosomiasis moderately and transiently inhibited the primary antibody response to these antigens, but had no effect on ongoing antibody production against keyhole limpet hemocyanin or on secondary responses to any of the antigens. Single doses of niridazole (which suppress cell-mediated immune responses) had no effect whatsoever on the most strongly inhibited of the primary antibody responses, that to alum-precipitated polymerized human serum albumin.     

Effect of a single exposure to ultraviolet radiation on Mycobacterium bovis bacillus Calmette-Guerin infection in mice

BALB/c and C3H mice were exposed on the dorsal skin to 45 kJ/m2 of UVB radiation from FS-40 sunlamps 3 days before infection with 1 x 10(6) live units of Mycobacterium bovis bacillus Calmette-Guérin (BCG) (Tice strain) in the footpad. At regular intervals, groups of mice were tested for a delayed type hypersensitivity (DTH) response to the purified protein derivative (PPD) of tubercle bacilli, and the course of infection was monitored by measuring the size of the infected footpad, enlargement of the draining lymph node, and the number of bacteria in the spleen and lymph node. In both strains the DTH response to PPD was significantly delayed in UV-treated mice compared to unirradiated mice, when tested 21 and 42 days after BCG infection. By day 50, no significant difference was detected in the DTH response between irradiated and unirradiated mice. UV treatment reduced the size of the lymph node draining the site of BCG infection in both strains of mice and the size of the infected footpad in C3H mice but not in BALB/c mice. In both strains of mice the total number of bacteria in the spleen and the draining lymph node increased after UV irradiation. When irradiated 3, 5, 18, or 21 days after BCG infection, BALB/c mice also showed a significant decrease in their DTH response to PPD, indicating that the UV-induced suppression of BCG occurs both at the induction and the elicitation stages of the immune response. Thus, mice exposed to a single dose of UV radiation either before or after BCG infection showed an impaired DTH response to mycobacteria, which was accompanied by an increase in the multiplication of bacteria in the tissues, even though the organisms were introduced at an unirradiated site. These studies demonstrate that a systemic effect of UV irradiation can interfere with the development and expression of immunity to pathogenic bacteria in mice.     

Delayed-type hypersensitivity to Babesia microti-infected erythrocytes in mice

Strong delayed-type hypersensitivity (DTH) to Babesia microti was elicited when intraerythrocytic parasites (IEP) were inoculated subcutaneously into the flank of normal mice 6 to 14 days before challenge in the ipsilateral footpad with 10(8) IEP. Intraperitoneal or intravenous administration of antigen did not sensitize mice for DTH. When challenge was given 21 days after immunization, the response was approximately half of the maximum and then rose again slowly over the next 3 weeks to levels that were not significantly different from those maximal values. The response was similar in seven strains of mice, regardless of sex. The response was classified as a true DTH reaction on the basis of kinetics, histology, and the transfer of responsiveness with immune T lymphocytes of the Ly 1+ phenotype, but not with serum. The reaction was specific for IEP since control groups given two injections of red blood cells from uninfected syngeneic mice (NRBC) or one injection of NRBC or sheep red blood cells (SRBC) and one of IEP never developed significant footpad swelling. Freed parasites obtained by osmotic rupture, density gradient sedimentation, and lethally irradiated IEP were also effective for elicitation of DTH. Anti-IEP DTH was expressed in a dose-dependent fashion with 10(6), 10(7), or 10(8) parasites sufficing for immunizing inoculum as long as 10(8) parasites were used as the challenge dose. Mice immunized and challenged with 10(8) lethally irradiated IEP (60 krad, 60Co), were protected against subsequent intraperitoneal challenge with 10(8) viable IEP. If mice were infected intraperitoneally with 10(8) IEP at any time between 21 days before immunization to 2 hr after challenge, their ability to respond to immunization and challenge was profoundly depressed. These data suggest that development of a strong anti-parasite DTH response can occur in parallel with resistance to infection, but is not a rapid sequela of bloodborne infection.