Regulation of delayed-type hypersensitivity. II. Specific suppressor factor for delayed-type hypersensitivity to sheep erythrocytes in mice.

An antigen-specific suppressor factor for delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) in mice is described. Lymph node cells and spleen cells from mice injected intravenously with 1 x 10(9) SRBC 4 days previously were incubated in vitro for 48 h in culture medium. Supernatant obtained from the culture inhibited the induction of DTH to SRBC in normal mice. It also suppressed the expression of DTH in presensitized mice. The suppression is specific as the suppressor factor had no effect on the DTH to noncross-reacting antigen, chicken red blood cells. Treatment of the spleen cells with anti-theta serum and complement prevented the production of the suppressor factor, whereas treatment with anti-Ig serum and complement had no effect. Suppressor factor produced by H-2k mice suppressed the DTH in H-2b mice. The factor thus seems to act across the H-2 barrier. The suppressor factor was not removed by adsorption with goat anti-mouse immunoglobulin immunoadsorbent, but could be adsorbed by SRBC. It was stable at 56 degrees C for 1 h, but was partially inactivated by freezing and thawing. The factor has a molecular weight of less than 35 000 daltons.     

Regulation of delayed-type hypersensitivity. I. T suppressor cells for delayed-type hypersensitivity to sheep erythrocytes in mice.

Mice injected with 1 X 10(8) sheep red blood cells (SRBC) into the footpad showed high levels of delayed-type hypersensitivity (DTH) to SRBC 4-8 days after the injection. In contrast, mice injected intravenously with 1 X 10(9) SRBC were unresponsive to DTH induction through 1 X 10(8) SRBC injected into the footpad. This suppression of DTH was maintained for at least 6 weeks and was transferable spleen, lymph node and thymus cells to normal syngeneic recipients. Bone marrow cells, on the other hand, did not contain the suppressor cells. The suppression of DTH was antigen-specific in that DTH to chicken red blood cells and contact sensitivity to 2,4-dinitrofluorobenzene was not affected. The suppressor cells were theta-positive and Ig-negative. They appeared in the spleen in optimum number 3-4 days after induction. The suppressor cells affected both the induction and manifestation of DTH. The presence of suppressor and effector cells for DTH inducible by different routes of antigenic presentation reflects the dynamic balance in the regulation of DTH.     

Regulation of delayed-type hypersensitivity IV. Antigen-specific suppressor cells for delayed-type hypersensitivity induced by lipopolysaccharide and sheep erythrocytes in mice.

Mice injected subcutaneously with 1 x 10(8) sheep red blood cells (SRBC) developed high levels of delayed-type hypersensitivity (DTH) to SRBC 4-8 days after injection. Such DTH was suppressed when 100 microgram lipopolysaccharide (LPS) was injected intravenously 1-2 days before or at the time of SRBC injection. This suppression of DTH was transferable by spleen, lymph node, thymus and bone marrow cells to sensitized or normal syngeneic recipients, but could not be transferred by serum. Suppressor cells were not induced by LPS alone or SRBC alone, and they were antigen-specific since DTH to chicken red blood cells was not affected. The suppressor cells appeared in the spleen in optimum number 3-4 days after induction. They were theta-negative and Ig-positive as judged by antiserum plus complement treatment and by Ig rosette separation. Attempts to obtain soluble suppressor factor from the suppressor cells by sonication or in vitro incubation were unsuccessful. Mitomycin C treatment of the suppressor cells completely abolished the suppressor activity. Thus, LPS, in conjunction with antigen, appears to induce a population of specific suppressor B cells which are capable of regulating T cell function.     

Suppression of delayed-type hypersensitivity reactions and lymphokine production by cyclosporin A in the mouse.

Two consecutive daily i.m. injections of cyclosporin A (Cs A) (greater than 50 mg/kg) inhibited delayed type hypersensitivity (DTH) responses in mice immunized with SRBC. Maximal suppression was observed when Cs A was administered 24 and 48 h after sensitization. Culture of spleen cells from these animals with antigen, insoluble concanavalin A (iCon A) or PHA revealed inhibition of the production of two lymphokines: that inducing macrophage procoagulant activity (MPCA) and macrophage chemotactic factor (LDCF). The inhibitory effect on lymphokine production was not due to depletion of T cells. In vitro, 25 ng/ml Cs A suppressed T cell proliferative responses to antigen and mitogen but much higher doses were required to impair the response to LPS. Similar doses of Cs A also suppressed lymphokine production, but the responses of macrophages to these lymphokines was unaffected, even at doses which totally inhibited lymphokine production. Production of interleukin 1 by LPS stimulated macrophages was inhibited by Cs A only at concentrations much greater than those required to suppress lymphokine production.     

Regulation of delayed-type hypersensitivity. III. Effect of cyclophosphamide on the suppressor cells for delayed-type hypersensitivity to sheep erythrocytes in mice.

A previous study (Eur. J. Immunol. 1977. 7: 714) has shown that mice injected intravenously (i.v.) with 4 x10(9) sheep red blood cells (SRBC) produce cells which suppress delayed-type hypersensitivity (DTH). These suppressor cells are theta-positive, antigen-specific and act via a soluble factor which does not bear immunoglobulin determinants (Eur. J. Immunol. 1978. 8: 168). The present paper demonstrates that these suppressor cells are inhibitable by cyclophosphamide (CY). Mice injected with graded amounts of CY two days prior to SRBC injection, showed maximum augmentation of DTH at 200 mg/kg body weight, a dose which completely suppressed the appearance of splenic plaque-forming cells (PFC) to SRBC. In contrast, lower doses of CY enhanced both DTH and PFC responses. Time course studies showed that CY inhibited the precursors of suppressor cells and had little or no effect on suppressor cells which have already encountered antigens. This was further confirmed by passive transfer studies which showed tha- suppressor cells were inhibited if CY was administered at the same time or 2 days before SRBC injection, but were not affected if CY was given after antigen stimulation. Direct evidence for the effect of CY on suppressor cells was obtained by cell fractination with a Ficoll density gradient. The denser suppressor cell population was absent from the spleens of mice treated with 200 mg/kg of CY 2 days before i.v. injection with 1 x 10(9) SRBC.     

Regulation of delayed-type hypersensitivity V. Suppressor cell memory in antigen-specific suppression of delayed-type hypersensitivity to sheep erythroeytes

Mice primed i. v. with 10⁹ sheep red blood cells (SRBC) produce antigen-specific T suppressor (Ts) cells which inhibit both the induction and the expression of delayed-type hypersensitivity (DTH). These Ts cells are detectable in the spleen and lymph nodes 3–5 days after priming but are largely absent by 6 days. The transient detect-ability of the Ts cells contrasts sharply with the profound antigen-specific suppression which persists in primed donor mice for at least a year. Evidence is presented that this long-term impairment of DTH is maintained, at least in part, by memory Ts cells which are Thy-1⁺, cyclophosphamide-resistant and antigen-specific. Although they appear to be co-induced with the short-lived primary Ts cells and localize initially in the lymphoid organs, they are present in the long-lived circulating pool of T cells and can be adoptively transferred by celomic parabiosis. Memory Ts cells are readily reactivated by lower doses of SRBC which would induce T effector cells rather than Ts cells in naive animals. Reactivated memory Ts cells seem to generate a population of antigen-specific secondary Ts cells which again localizes in the lymphoid organs and can adoptively suppress the induction and expression of DTH to SRBC.     

Distinction between suppressors of the delayed-type hypersensitivity and the humoral response to sheep erythrocytes.

Suppressors for both delayed-type hypersensitivity (DTH) and the humoral immune response could be simultaneously induced in the spleens of mice by immunization with a high dose of SRBC. Normal recipient mice of the spleen cells from donors immunized 5 days previously elicited depressed DTH or humoral response when immunized with SRBC. The suppressive activity was found to reside in T not B enriched fraction. Four hundred rad irradiation of the primed spleen cells resulted in complete loss of DTH suppressor activity, but only in some reduction of the suppressor activity for the humoral response. In contrast, hydrocortisone treatment of the donor mice caused no loss of DTH suppressor activity while approximately half of the suppressive activity for anti-SRBC PFC response was lost. Adult thymectomy prevented completely the induction of the DTH suppressor in contrast to little loss of the suppressor activity for the humoral response. DTH suppression was antigen-specific for the induction, but nonspecific for the expression. However the suppression of the humoral response was antigen-specific not only for the induction but also for the expression. In addition, DTH suppressor was capable of suppressing both the induction and expression of DTH while the humoral response was suppressed only in the induction stage by the suppressor.     

Improved quantitation of delayed-type hypersensitivity responses to sheep erythrocytes in the mouse footpad by estimation of 125I-fibrin deposition

Footpad swelling in response to subcutaneous antigen challenge is widely used to assess delayed-type hypersensitivity responses to xenogeneic erythrocytes in mice. We report here that quantitation of the deposition of 125I-fibrin, compared with that of 125I-human serum albumin, following intravenous isotope administration, provides a less subjective, convenient and antigen specific index of cell-mediated immunity. Moreover, the results obtained correlate well with in vitro assessment of antigen-specific T cell responses.     

Genetic control of Salmonella typhimurium-induced depression of delayed-type hypersensitivity to sheep erythrocytes in mice.

Infection of mice with a temperature-sensitive mutant of Salmonella typhimurium C5TS allowed the survival of genetically susceptible mice. The ability to mount a delayed-type hypersensitivity (DTH) response to sheep erythrocytes during infection with C5TS was studied in various inbred mouse strains, recombinant inbred strains derived from C57BL/6 (susceptible) and A/J (resistant) mice, and C3H congenic mice. Suppression of the DTH response to sheep erythrocytes was found in mice that carried the Itys allele, the H-2b haplotype, or both. These genes are known to increase susceptibility to S. typhimurium infection. In contrast, no DTH response suppression was observed in mouse strains that carried other genes that increased susceptibility to S. typhimurium, e.g., DBA/2 and C3H/HeJ. Apart from a transient suppression in A/J mice, the DTH responses of resistant mice (A/J and CBA) were normal or increased. The DTH response to sheep erythrocytes could be restored in immunodepressed mice by increasing the immunizing dose, suggesting the possible role of activated macrophages in depression of the DTH response.     

Cyclosporin A prevents suppression of delayed-type hypersensitivity in mice immunized with high-dose sheep erythrocytes.

When administered intraperitoneally to mice 2 days before immunization with a tolerogenic dose (10(9)) of sheep red blood cells (SRBC), cyclosporin A (CsA; 200 mg/kg) strikingly augmented 4-day delayed-type hypersensitivity (DTH) footpad reactions. These enhanced responses were similar in magnitude to those seen in animals sensitized with an immunogenic, low-dose (10(6)) SRBC. The stimulatory effect of CsA was observed over the dose range of 5-200 mg/kg and was obtained in animals given the drug in one injection, up to 7 days before sensitization. The augmentation of DTH was characterized by footpad swelling, intense mononuclear cell infiltration and increased deposition of 125I-fibrinogen within the challenge site. In addition, increased expression of procoagulant activity by spleen cells in response to antigen was observed. Cell transfer experiments showed that the CsA-enhanced DTH could be adoptively transferred to naive recipients. Additional transfers conducted at the time of antigen challenge suggested that, under the conditions described, CsA inhibited the action of a population of suppressor cells normally effective during DTH reactions.     

Effect of irradiation on the precursor, activated and memory suppressor T cells for delayed-type hypersensitivity to sheep erythrocytes in mice.

The relative radiosensitivities of precursor (Tsp), activated (Ts) and memory (Tsm) suppressor T cells for delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) were investigated in mice. Spleen cells from CBA mice, primed i.v. with 10(9) SRBC 3-4 days previously, contain specific Ts cells which substantially impair the induction of DTH to SRBC in normal syngeneic recipients. Exposure of mice to 400 rad irradiation 1 day before the priming completely eliminated the subsequent development of Ts cells. In contrast, 3 days after the priming injection, Ts cell activity in mice is resistant to doses higher than 600 rads. Mice primed 40 days previously with 10(9) SRBC contain Ts-cell memory which can be readily recalled by i.p. injection of 10(8) SRBC. The secondary Ts cells which specifically inhibit DTH induction can be demonstrated adoptively in normal recipients. Mice were exposed to various doses of irradiation 40 days after the priming and 1 day before the i.p. injection. Ts memory was significantly reduced by 300 rads and was completely abrogated by 400 rads. The relative radiosensitivities of the three subsets of suppressor T cells are in the order of Tsm = Tsp greater than Ts.     

Specific suppression of delayed hypersensitivity response to sheep erythrocytes by heterologous anti-lymphocyte serum.

The development of a heterologous anti-lymphocyte serum (ALS) capable of specifically suppressing the delayed hypersensitivity (DH) response is reported. This ALS, termed ALS(CMI), was prepared against lymph node cells from rats which had been immunized against sheep erythrocytes (SRBC) following treatment with cyclophosphamide which is known to enhance the DH response and suppress the humoral immune response. The effect of ALS(CMI) on the primary DH response to SRBC using the footpad swelling test was studied. Its effect on the primary humoral immune response to SRBC was also studied using the Jerne plaque assay technique. ALS(CMI) suppressed the humoral antibody response to SRBC and the DH response to a third party antigen only when administered before the antigen, having no effect when administered post-antigenically. On the other hand, ALS(CMI) significantly suppressed the primary DH response to SRBC when administered either before or after the antigen.     

Restoration of delayed hypersensitivity to sheep erythrocytes by thymosin treatment of T-cell-depleted mice.

Calf thymosin was injected subcutaneously in daily doses of 0.1 to 3 mg for 12 to 15 days into adult thymectomized, irradiated, bone marrow-reconstituted (THXB) mice. Thymosin partially restored the ability of the T-cell-depleted host to develop delayed-type hypersensitivity to sheep erythrocytes. The degree of restoration varied from 50 to 75% of control values. Thymosin treatment of normal mice potentiated the footpad responsiveness to sheep erythrocytes by as much as 50% over that of untreated controls. The optimum dosage of thymosin seemed to be in the 200- to 500-mug range, and multiple injections were essential for a significant response. Tweleve daily injections of 100 to 500 mug of thymosin restored T-cell reactivity to the THXB mouse, but the responsiveness decayed relatively rapidly once the treatment was stopped. The restoration of immune responsiveness to sheep erythrocytes in T-cell-depleted mice provides a convenient means of demonstrating activity in thymosin preparations in vivo.     

Inhibition of the immune response of mouse spleen cells to sheep erythrocytes in vitro by anti-immunoglobulin sera

The effect of anti-immunoglobulin sera on the antibody response of both non-sensitized and sensitized mouse spleen cells in vitro has been studied. Antisera to immunoglobulin Fab gave almost complete inhibition of both IgM and IgG responses. Antisera to IgM suppressed the IgM but not the IgG response and conversely antisera to IgG classes caused some suppression of the IgG response but did not reduce the IgM response. These results have been discussed in terms of the nature of receptor molecules on lymphocytes responsible for recognition of antigen.     

Factors influencing the enhancement of delayed-type hypersensitivity to ovalbumin by cyclosporin A in the guinea pig: possible role of suppressor cells

Enhancement of delayed-type hypersensitivity (DTH) reactions to ovalbumin (OVA) was demonstrated in guinea pigs given a single, high dose of cyclosporin A (CsA) intraperitoneally, 2 days before immunization. Courses of oral CsA, commencing at the time of immunization and lasting until day 4 or 13 also resulted in augmented DTH responses at days 14 and 28, respectively. However, the enhancing protocol (CsA; day 0-4) did not significantly affect circulating anti-OVA antibody titres. The capacity to express increased DTH could be adoptively transferred to naive recipients by systemic injection pooled spleen and peritoneal exudate cells. Moreover, the expression of augmented responses was inhibited by transfer of cells from normally immunized donors. Although augmentation of DTH was accompanied by increased lymphocyte proliferative responses to OVA in vitro, there was no similar effect on T cell responses to polyclonal mitogens. The data support the view that augmentation of DTH by CsA is attributable to suppressor cell dysfunction, but that this is unlikely to be a non-specific suppressor cell impairment.     

Anti-schistosomal activity of cyclosporin A: studies on murine spleen cells and the influence of a cyclosporin antagonist on resistance to infection.

Mice were treated with 5-day courses of cyclosporin A (CsA) around the time of infection with Schistosoma mansoni. Recovery of lung-stage worms 4-8 days post-infection (p.i.) was substantially reduced (80%) and no sexually mature adults were recovered from the hepatic portal system at 7 weeks p.i. Flow cytometric analysis of spleen cells from CsA-treated animals during the period of maximal parasite attrition revealed transient reductions in CD3+ and CD4+ cells and in the CD4+: CD8+ ratio compared with drug vehicle-treated, infected controls. No significant numerical changes in B cells, macrophages or eosinophils were detected relative to vehicle-treated infected mice. Transfer of spleen cells from CsA-treated donors 8 days after infection failed to confer increased resistance to S. mansoni infection on untreated recipients. Moreover, concomitant administration of CsA and an inducer of interleukin-2 production (ADA-202-718) did not interfere with the anti-schistosomal effect of CsA. Despite our incomplete understanding of the in vivo properties of CsA and reports of its paradoxical effects on immune responses, these new data indicate that the influence of CsA in schistosomiasis is unlikely to be mediated by modulation of host cell mediated immunity. This contrasts with certain other anti-parasitic effects of CsA which appear to be mediated by an action on T cells.     

Rabies virus cross-reactive murine T cell clones: analysis of helper and delayed-type hypersensitivity function

Three T cell clones derived from rabies virus-immunized BALB/c mice were analysed for specificity and function. The clones proved to be broadly cross-reactive by responding to different rabies virus isolates (PM, ERA, CVS, HEP) and other representatives of the genus Lyssavirus, like the Duvenhage-6 (DUV6) and Mokola (MOK) viruses. The clones detected three different epitopes: an epitope expressed on the matrix protein (M) shared by PM, HEP, MOK and DUV6 viruses (clone AA8), an epitope expressed on the M-protein shared by PM, ERA, CVS, HEP and MOK viruses (clone 35A) and finally an epitope expressed on the glycoprotein (G-protein) shared by PM, ERA, CVS, HEP and MOK viruses (clone BG2). Antigen recognition of all clones proved to be MHC-restricted and they all displayed the CD4+ CD8- phenotype. Intravenous inoculation of the T cells in syngeneic mice, which had been injected intracutaneously in the ear with HEP virus, resulted in a localized DTH reaction characteristic for TH1 cells. In vitro, the clones were able to provide help to rabies virus-primed B cells, resulting in the production of virus-specific antibodies directed against all the four structural proteins of rabies virus. Further analysis of this antibody response revealed that part of it was directed against antigenic determinants of the G-protein which induce virus neutralizing antibody.     

Influence of route and dose of antigen on the migration inhibition and plaque-forming cell responses to sheep erythrocytes in the lizard, Calotes versicolor

The influence of route of administration and dose of antigen on the generation of humoral and cell-mediated immune (CMI) responses has been studied in the lizard, Calotes versicolor. Intramuscular (i.m.) immunization was found to be more suitable for the induction of both plaque-forming cell (PFC) and migration inhibition (MI) responses to sheep erythrocytes (SRBC) than the intraperitoneal (i.p.) route. The i.m. route favoured the development of quicker PFC as well as MI responses. The latter was observed to be sustained up to a month after immunization. In contrast, with the i.p. route of immunization, the peak PFC and MI responses appeared slowly and were followed by a sudden decline. An inverse relationship between PFC and MI functions was noted. The maximum level of MI was obtained with 10⁴ SRBC while the PFC response was greater with the higher doses of antigen. Low dose of antigen induced a strong and quick MI response with concomitant postponement of the PFC response. Incorporation of SRBC into Freund's complete adjuvant did not influence the MI level. After an injection of a supra-optimal dose of SRBC, the MI level was very low at a time when the PFC response was at its maximum and the degree of MI rose again after the decline in PFC number. Thus, the induction of antibody synthesis needs a higher threshold level of antigen for its full expression, in contrast to the minimal antigen dose required for MI response to SRBC in lizards.     

Contact and delayed hypersensitivity in the mouse: II. The role of different cell populations

Mice sensitized to oxazolone show contact sensitivity which can be assessed by painting oxazolone on the ear and measuring the increase in ear thickness at 24 hours. Contact sensitivity can be transferred passively by peritoneal exudate, lymph node and bone marrow cells. When CBA mice are challenged immediately after transfer, at a 3:1 donor recipient ratio, the peritoneal exudate cells give bigger transferred reactions than lymph node cells. The converse is true on challenge at 6 days after transfer, at which time the lymph node cells give bigger transferred reactions than the peritoneal exudate cells. These results suggest that different types or functional states of cells are involved in these two types of transfer.

The possibility that the successful transfer with delayed challenge by lymph node cells was due to active sensitization by antigen transferred with the cells, was made unlikely by passive transfer into `tolerant' recipients.

Mice first show contact sensitivity when challenged at 3 days (about 72 hours) after sensitization. The lymph nodes develop the ability to transfer contact sensitivity with delayed challenge at the same time but the bone marrow only acquires this activity at 5 days.