A stable form of delayed-type hypersensitivity

Oral Outbreak of Chagas Disease in Santa Catarina, Brazil: Experimental Evaluation of a Patient's Strain

Chagas disease is a worldwide public health problem. Although the vectorial transmission of Chagas disease has been controlled in Brazil there are other ways of transmission, such as the ingestion of T. cruzi contaminated food, which ensures the continuation of this zoonosis. Here, we demonstrate the influence of the inoculation route on the establishment and development of the SC2005 T. cruzi strain infection in mice. Groups of Swiss mice were infected intragastrically (IG) or intraperitoneally (IP) with the T. cruzi SC2005 strain derived from an outbreak of oral Chagas disease. The results revealed that 100% of IP infected mice showed parasitemia, while just 36% of IG infected showed the presence of the parasite in blood. The parasitemia peaks were later and less intense in the IG infected mice. Mortality of the IP infected animals was more intense and earlier when compared to the IG infected mice. In the IP infected mice leucopenia occurred in the early infection followed by leucocytosis, correlating positively with the increase of the parasites. However, in the IG infected mice only an increase in monocytes was observed, which was positively correlated with the increase of the parasites. Histopathological analyses revealed a myotropic pattern of the SC2005 strain with the presence of inflammatory infiltrates and parasites in different organs of the animals infected by both routes as well as fibrosis foci and collagen redistribution. The flow cytometric analysis demonstrated a fluctuation of the T lymphocyte population in the blood, spleen and mesenteric lymph nodes of the infected animals. T. cruzi DNA associated with the presence of inflammatory infiltrates was detected by PCR in the esophagus, stomach and intestine of all infected mice. These findings are important for the understanding of the pathogenesis of T. cruzi infection by both inoculation routes.

Dose-dependent induction of murine Th1/Th2 responses to sheep red blood cells occurs in two steps: antigen presentation during second encounter is decisive

The differentiation of CD4 T cells into Th1 and Th2 cells in vivo is difficult to analyze since it is influenced by many factors such as genetic background of the mice, nature of antigen, and adjuvant. In this study, we used a well-established model, which allows inducing Th1 or Th2 cells simply by low (LD, 10(5)) or high dose (HD, 10(9)) injection of sheep red blood cells (SRBC) into C57BL/6 mice. Signature cytokine mRNA expression was determined in specific splenic compartments after isolation by laser-microdissection. LD immunization with SRBC induced T cell proliferation in the splenic T cell zone but no Th1 differentiation. A second administration of SRBC into the skin rapidly generated Th1 cells. In contrast, HD immunization with SRBC induced both T cell proliferation and immediate Th2 differentiation. In addition, splenic marginal zone and B cell zone were activated indicating B cells as antigen presenting cells. Interestingly, disruption of the splenic architecture, in particular of the marginal zone, abolished Th2 differentiation and led to the generation of Th1 cells, confirming that antigen presentation by B cells directs Th2 polarization. Only in its absence Th1 cells develop. Therefore, B cells might be promising targets in order to therapeutically modulate the T cell response.

Validation of a Candida albicans delayed-type hypersensitivity (DTH) model in female juvenile rats for use in immunotoxicity assessments

Establishing an in vivo cell-mediated immunity (CMI) assay, such as the delayed-type hypersensitivity (DTH) assay, has been identified as an important gap and recommended to receive highest priority for new model development in several workshops on developmental immunotoxicity. A Candida albicans DTH model has recently been developed that has the advantage over other DTH models, which use alternative sensitizing antigens, in that antigen-specific antibodies, which may interfere with the assay, are not produced. In addition, the in vivo C. albicans DTH model was demonstrated to be more sensitive in detecting immunosuppression than DTH models using keyhole limpet hemocyanin (KLH) or sheep red blood cells as antigens, as well as some ex vivo CMI assays. While KLH and sheep red blood cells are non-physiological immunogens, C. albicans is an important human pathogen. The present studies were conducted in order to optimize and validate the C. albicans DTH model for use in developmental immunotoxicity studies using juvenile rats. Three known immunosuppressive compounds with different mechanisms of action were tested in this model, cyclosprorin A (CsA), cyclophosphamide (CPS), and dexamethasone (DEX). Animals were sensitized with formalin-fixed C. albicans on postnatal day (PND) 28 and challenged with chitosan on PND 38. Drug was administered beginning on PND 23 and continued until PND 37. Exposure to each of the three immunotoxicants resulted in statistically significant decreases in the DTH response to C. albicans-derived chitosan. Decreases in footpad swelling were observed at ≥10 mg CsA/kg/day, ≥5 mg CPS/kg/day, and ≥0.03 mg DEX/kg/day. These results demonstrate that the C. albicans DTH model, optimized for use in juvenile rats, can be used to identify immunotoxic compounds, and fills the need for a sensitive in vivo CMI model for assessments of developmental immunotoxicity. Abbreviations Ab, antibody APC, antigen presenting cell BSA, bovine serum albumin C. albicans, Candida albicans CI, challenge interval CMI, cell-mediated immunity CO, challenge only CPS, cyclophosphamide CsA, cyclosporin A CTL, cytotoxic T lymphocyte DEX, dexamethasone DIT, developmental immunotoxicity DTH, delayed-type hypersensitivity ip, intraperitoneal KLH, keyhole limpet hemocyanin MLR, mixed lymphocyte reaction OVA, ovalbumin PBS, phosphate-buffered saline PND, postnatal day sc, subcutaneous SEM, standard error of the mean SRBC, sheep red blood cells.

Evaluation of antiallergic and anti-anaphylactic activity of ethanolic extract of Sanseveiria trifasciata leaves (EEST) in rodents

AIM OF THE STUDY

The leaves and rhizomes of Sansevieria trifasciata are used in folk medicine for treating bronchitis, asthma, cough, snake bite and insect bite etc. The ethanolic extract elicited analgesic, anti-inflammatory and antipyretic activity. Hence, it was decided to study the antiallergic activity of ethanolic extract of S. trifasciata (EEST) on various animal models as well as in vitro conditions, and also to understand possible mechanism of action.

MATERIALS AND METHODS

Ethanolic extract of S. trifasciata leaves (EEST) were prepared by cold maceration followed by concentration and evaporation under reduced pressure on a rotary evaporator to obtain semisolid mass. The various phytoconstituents were analyzed. The acute toxicity study of EEST was carried out in mice. The antiallergic and anaphylactic activities were evaluated using animal models viz. milk induced eosinophilia and leukocytosis, compound 48/80 induced mast cell degranulation, active and passive cutaneous anaphylaxis and histamine induced pedal edema. In addition, EEST effect on Shultz-Dale reaction in sensitized guinea pig ileum in ex vivo and antioxidant activity by free radical scavenging by DPPH method (in vitro) were also studied.

RESULTS

EEST treatment at 100mg/kg and 200mg/kg p.o inhibited (a) milk-induced increased eosinophilia, leukocytosis, monocytes and neutrophils. (b) Prevented passive cutaneous and active anaphylactoid reactions. (c) Prevented compound 48/80 induced degranulation of sensitized mesenteric mast cells. (d) Inhibited histamine induced pedal edema formation significantly. EEST pretreatment inhibited Shultz-Dale reaction in guinea pig ileum and also elicited potent antioxidant activity.

CONCLUSION

Experimental findings demonstrate promising antiallergic and anti-anaphylactic activity of EEST and also elicited potent antioxidant activity. The antiallergic and anti-anphylactic activity might be due to inhibition of release of chemical mediators from mast cells largely by phytoconstituents like steroidal saponins, triterpenoids and flavonoids present in EEST.

Validation of the Candida albicans delayed-type hypersensitivity (DTH) model in the female B₆C₃F₁ mouse for use in immunotoxicological investigations

Although numerous models are used to evaluate the immunotoxic effects of xenobiotics on cell-mediated immunity (CMI), no holistic model for evaluating such effects on the delayed-type hypersensitivity (DTH) response has gained widespread acceptance. Due to a lack of interference from antigen-specific antibody production, the Candida albicans DTH model has recently been demonstrated to be a more appropriate model for assessing effects on CMI than other DTH models that utilize different sensitizing antigens, such as sheep erythrocytes (SRBC) or keyhole limpet hemocyanin (KLH). The present studies were conducted to validate the C. albicans DTH model for its ability to detect suppression (or the lack thereof) of CMI following exposure for 28 days to well-characterized immunosuppressive drugs, each having a different mechanism of action. The compounds evaluated included azathioprine (AZA), cyclophosphamide (CPS), cyclosporin A (CSA), dexamethasone (DEX), and the non-immunotoxic compound, benzo[e]pyrene (B[e]P). Exposure to each of the four known immunotoxicants resulted in statistically significant decreases in the DTH response to C. albicans. Footpad swelling was decreased following exposure to AZA at ≥ 20 mg/kg but not at 10 mg/kg, CPS at ≥ 10 mg/kg but not at 5 mg/kg, CSA at ≥ 3 mg/kg but not at 1 mg/kg, or DEX at ≥ 0.3 mg/kg (intermittently at 0.1 mg/kg) but not at 0.03 mg/kg. As expected, exposure to B[e]P for 28 days at doses up to 40 mg/kg had no effect on the DTH response. These results demonstrated that the C. albicans DTH assay in the B₆C₃F₁ mouse was capable of appropriately classifying each test article as to its immunotoxic effects on CMI. Furthermore, comparisons of these results with previous reports of effects on ex vivo CMI end points suggest that this DTH assay may be more sensitive than standard ex vivo assays at detecting immunosuppressive effects.

ExperimentalLeishmania (L.) amazonensisLeishmaniasis: Characterization and Immunogenicity of Subcellular Fractions

A technique developed in Trypanosoma cruzi biochemical studies was successfully used to fractionate Leishmania (Leishmania) amazonensis promastigotes. Ultrastructural analyses revealed a membrane fraction (MF) associated to subpellicular microtubules, a ribosomal-rich microsomal fraction (MicF), and a flagellar fraction (FF) free of associated membrane. All fractions proved to be immunogenic through delayed type hypersensitivity reaction assays. Therefore, a protocol was designed to test whether these fractions could elicit a protective response in mice infected by L. (L), amazonensis. The protocol consisted of a BCG injection (as cellular immunity inducer), followed by cyclophosphamide (once its cytotoxic effect is over, this immunosuppressor can increase the number of circulating leukocytes), then an injection with one of the fractions followed by a challenge. When compared to infected control animals, mice injected with any of the fractions presented a smaller footpad swelling, especially those injected with MicF or FF. Macroscopically, immunized mice under modulation by BCG presented no swelling. Histopathological studies performed on day 120 revealed fewer amastigotes and more intense inflammation in lesions of MicF and FF injected mice. Animals injected with MF presented an intermediate pattern. Parasite quantification corroborated these results. The results show that all fractions are potent immunostimulators, but MicF and FF have the strongest protective ability.

Different immune correlates associated with tumor progression and regression: implications for prevention and treatment of cancer

Observations show that humans and animals respond immunologically to most cancers. Why does the immune system then fail to control cancer? We argue from the literature that there is a commonality in the regulation of responses against most murine tumors, and that a major mechanism of escape may be deviation of an effective Th1, cytotoxic T lymphocyte response to a less effective response with a Th2 component. We examined this hypothesis with two well-studied murine tumors. We found, following primary tumor implantation, that resistance correlates with Th1 responses and IgG2a antibody production and progression with mixed Th1/Th2 responses and production of IgG1 and IgG2a antibodies. Resistance is associated with a modulation of the anti-tumor response towards the Th1 pole in both systems. We conclude that the immune responses against these two tumors are in accord with our hypothesis, and argue that this is likely to be true of many human and murine tumors. The correlation of IgG isotype of anti-tumor antibody with the Th1/Th2 nature of the anti-tumor response readily allows one to longitudinally monitor the changing nature of the anti-tumor response. We suggest that such monitoring can guide immunotherapy to maximize the effectiveness of the host's immune response against cancer.

IL-1beta, but not IL-1alpha, is required for antigen-specific T cell activation and the induction of local inflammation in the delayed-type hypersensitivity responses

As IL-1 expression is augmented in delayed-type hypersensitivity (DTH) responses, we analyzed the role of IL-1 in this response. DTH responses against methyl BSA (mBSA) were significantly suppressed in IL-1beta-deficient (IL-1beta-/-) and IL-1alpha/beta-/- mice, but not in IL-1alpha-/- mice. In contrast, responses in IL-1R antagonist-/- (IL-1Ra-/-) mice were exacerbated. Lymph node cells derived from mBSA-sensitized IL-1beta-/-, IL-1alpha/beta-/- and IL-1R type I (IL-1RI)-/- mice, but not from IL-1alpha-/- mice, exhibited reduced proliferative responses against mBSA, while these from IL-1Ra-/- mice demonstrated augmented responses. DTH responses in wild-type mice following adoptive transfer of CD4+ T cells from mBSA-sensitized IL-1alpha/beta-/- mice were also reduced, while those in mice given cells derived from IL-Ra-/- mice were increased. DTH responses in IL-1RI-/-, but not IL-1alpha/beta-/-, mice were reduced upon transplantation of mBSA-sensitized CD4+ T cells from wild-type mice. The recall response of mBSA-sensitized CD4+ T cells against mBSA decreased upon co-culture with dendritic cells (DCs) from IL-1RI-/- mice, while the responses were normal with DCs from IL-1alpha/beta-/- mice. DTH responses in tumor necrosis factor alpha-/- (TNF-/-) mice were also suppressed; the magnitude of the suppression in IL-1alpha/beta-/-TNF-/- mice, however, was similar to that observed in IL-1alpha/beta-/- mice. These observations indicate that IL-1 possesses dual functions during the DTH response. IL-1beta is necessary for the efficient priming of T cells. In addition, CD4+ T cell-derived IL-1 plays an important role in the activation of DCs during the elicitation phase, resulting in the production of TNF, that activate allergen-specific T cells.

Morphological quantitative changes in the number of lymphocytes, macrophages and plasma cells in the uterus and lymph nodes of rats exposed to the systemic administration of BCG

This study was designed to investigate the effect of systemic administration of BCG on the morphological quantitative changes in the number of lymphocytes, macrophages and plasma cells in the uterus and lymph nodes of rats. Thirty female virgin Wistar Albino rats, aging 6 months and weighing between 200-250 g, were assigned to the two experimental groups; BCG treated and controls (n = 15). BCG group received 0.1 ml BCG in tail skin and control group received 0.1 ml saline at the same place. Two weeks after injections, rats in both groups were anesthesized with a high dose of ether and decapitated. Uterus and ileocecal lymph nodes were processed to determine a napthyl acid esterase (ANAE)-positive T lymphocytes and macrophages. The plasma cells were stained with the methyl green-pyronin method. It was found that the numbers of T lymphocytes, macrophages and plasma cells in the uterus and the ileocecal lymph nodes of BCG treated group significantly increased indicating the presence of an immune response to the systemic BCG administration. It was concluded that the systemic administration of BCG increases humoral and cellular immunity in endometrium, myometrium and regional lymph nodes. The immune deficiency system plays an important role in the pathogenesis of endometriosis. Therefore, the endometriosis might be prevented by using periodical administration of BCG. However, further experimental and clinical studies associated with these issue are required.

Study of acute chagasic mice under immunosuppressive therapy by cyclosporin A : modulation and confocal analysis of inflammatory reaction

The in vivo effects of cyclosporin A (CsA) on Trypanosoma cruzi infection were examined using different schedules of the drug in mice infected with the Y strain. Parasitaemia at day 8 after infection among CsA-treated animals was usually higher than control infected non-treated mice. On the other hand, mortality analysis showed that animals CsA-treated either with 200 mg/kg 2 days before infection or with therapeutic doses (10 mg/kg every other day) showed almost the same mean time of death (35.8 and 38.2 days, respectively). In these groups mice died 50% less than control infected non-treated ones. The mean time of death in the animals treated with 200 mg/kg 5 days after infection and in infected non-treated control mice were respectively 29.0 and 22.6 days. The kinetics analysis of the leukocyte population of animals treated with a single dose of 200 mg/kg of CsA before or after infection did not show the alternate pattern of leukopenia/leukocytosis observed in control groups of infected mice but differential cell counts indicated a modulatory action upon circulating leukocytes of therapeutic doses of CsA. The animals treated with any of the CsA schedules showed a moderate to intense diffuse inflammatory reaction exhibiting mainly mononuclear cells in the heart. Immunofluorescence analysis by confocal microscopy revealed that macrophages are a major component of the inflammatory infiltrate in all groups of CsA-treated mice and also in the control group.

Evaluation of cell-mediated immunity and circulating immune complexes as prognostic indicators in cancer patients

Cell-mediated immunity (CMI) and circulating immune complexes (CIC) were estimated in 55 cancer patients and 25 control volunteers to evaluate their prognostic significance. Cancer patients comprised head and neck cancer (11), breast cancer (13), gastrointestinal cancer (10), genitourinary cancer (11), and lymphomas and sarcomas (10). CMI was tested in vitro by early rosette-forming cells (ARFC) and total rosette-forming cell (TRFC) counts. ARFC count in control group was 758.1 +/- 78.09 cells/cumm. In advancing clinical stages of cancer (I-IV), ARFC counts were decreased (i.e., 601.12 +/- 74.96 [p < 0.01]; 494.8 +/- 71.83 [p < 0.001]; 432.44 +/- 36.05 [p < 0.001], and 438.55 +/- 69.99 [p < 0.001] cells/cumm, respectively). TRFC count in control group was 1029 +/- 88.39 cells/cumm. In cancer stages I through IV, these counts decreased significantly (i.e., 699.63 +/- 66.24; 597.55 +/- 82.9; 505.11 +/- 52.56; and 501.55 +/- 69.99 cells/cumm, respectively [p < 0.001]. Dinitrochlorobenzene cutaneous reactivity in vivo was 100% positive in control group, 62.5% positive in cancer stage I, 5% positive in stage II, and negative in stages III and IV. CIC of intermediate size were estimated by polyethylene glycol precipitation (PEG pptn) technique, which detects CIC in the ratio of 2:1 (Ag2Ab). Mean PEG index in control group was 39.5 +/- 4.65; sequential increase in CIC was observed in advancing clinical stages of cancer (I-IV)(i.e., 49 +/- 7.03 [p < 0.01]; 75.38 +/- 44.01 [p < 0.001]; 93.38 +/- 44.57 [p < 0.001]; and 216.00 +/- 147.05 [p < 0.001], respectively). Latex agglutination inhibition (LAI) titer was done to detect CIC as small as 8s, which constitute the opposite polar end of CIC spectrum. LAI titers in control group were nil. However, LAI titers in cancer stages I through IV were 1 +/- 2.64; 8.6 +/- 5.6 (p < 0.001); 12.00 +/- 8.11 (p < 0.001); and 25.77 +/- 9.06 (p < 0.001), respectively. Decrease in CMI and subsequent increase in CIC indicate unfavorable prognosis in cancer patients, and also precede clinical manifestation of increased tumor mass in vivo.

Interleukin-12 in infectious diseases

Interleukin-12 (IL-12) is a potent immunoregulatory cytokine that is crucially involved in a wide range of infectious diseases. In several experimental models of bacterial, parasitic, viral, and fungal infection, endogenous IL-12 is required for early control of infection and for generation and perhaps maintenance of acquired protective immunity, directed by T helper type 1 (Th1) cells and mediated by phagocytes. Although the relative roles of IL-12 and gamma interferon in Th1-cell priming may be to a significant extent pathogen dependent, common to most infections is that IL-12 regulates the magnitude of the gamma interferon response at the initiation of infection, thus potentiating natural resistance, favoring Th1-cell development; and inhibiting Th2 responses. Treatment of animals with IL-12, either alone or as a vaccine adjuvant, has been shown to prevent disease by many of the same infectious agents, by stimulating innate resistance or promoting specific reactivity. Although IL-12 may enhance protective memory responses in vaccination or in combination with antimicrobial chemotherapy, it is yet unclear whether exogenous IL-12 can alter established responses in humans. Continued investigation into the possible application of IL-12 therapy to human infections is warranted by the role of the cytokine in inflammation, immunopathology, and autoimmunity.

Bacille Calmette Guérin and interleukin-12 down-modulate interleukin-4-producing CD4+ NK1+ T lymphocytes

Early production of interleukin-12 (IL-12) by macrophages and of IL-4 from CD4+ NK1+ T cells influence development of the acquired immune response against infectious agents, namely differentiation of interferon-gamma-secreting T helper 1 (Th1) cells against intracellular pathogens and of IL-4-producing Th2 cells against helminths. Evidence has been presented for transient convertibility of Th1 and Th2 cells in the presence of the polarizing cytokines IL-4 or IL-12, respectively. Moreover, it is likely that IL-4 dominates over IL-12, suggesting that Th2 cell development is preferred in the presence of both cytokines. Mycobacterium bovis Bacille Calmette Guerin (BCG) and IL-12 are potent inducers of Th1 responses. Here we show that BCG and IL-12 down-modulate IL-4-producing CD4+ NK1+ TCR alpha/beta(intermediate) liver lymphocytes. Our data provide further insights into the mechanisms by which BCG and IL-12 may promote unrestricted development of Th1 responses in vivo: BCG and IL-12 not only provide the positive stimuli for Th1 cell differentiation, but also interfere with antagonizing signals.

Adjuvants, endocrines and conserved epitopes; factors to consider when designing "therapeutic vaccines"

Research into immunity to complex intracellular parasites has recently placed emphasis on the identification of peptide sequences recognised by T-cells, often with the dual objectives of finding species-specific protective epitopes, and of understanding selection of Th1 versus Th2 response patterns. In this review it is suggested that although such work is interesting, it will not achieve these objectives, which must, however, be addressed before we can design the new generation of therapeutic vaccines which may eventually replace antimicrobial drugs in the treatment of infection. First, we suggest that the balance of Th1 to Th2 lymphocyte activity is not determined by epitopes, but rather by adjuvant effects of microbial components which we have barely begun to define, and local endocrine effects mediated by conversion of prohormones into active metabolites by enzymes in lymph node macrophages. Cytokines play a role as mediators within these pathways. In chronic disease states there is a tendency for T-cell function to shift towards Th2. We describe immunopathological consequences of this tendency, including a putative role for agalactosyl IgG, and review evidence for involvement of changes in the endocrine system, brought about not only by the cytokine-hypothalamus-pituitary-adrenal axis, but also by direct actions on peripheral endocrine organs of excess levels of cytokines such as TNF alpha, TGF beta and IL-6. We summarise evidence that the epitopes that are targets for protective cell-mediated responses to complex organisms are usually not species specific. In tuberculosis, cellular responses to species-specific components appear to be associated with immunopathology rather than protection. Finally, we discuss how application of these principles has led to remarkable results in the immunotherapy of tuberculosis, including multidrug-resistant disease.

T-cell adjuvants

T-cell adjuvancy involves the use of agents to stimulate preferentially delayed type hypersensitivity (DTH). Traditional adjuvants like Alum, Freunds, muramyl peptides, and endotoxins are not selective. Natural infection (e.g. vaccinia) may yield selective DTH. Low dose cyclophosphamide (CY) with mycobacteria was the first experimental T-cell adjuvant. New adjuvant formulations (ISCOMS, MAPS, etc.) with synthetic T-cell epitopes offer improved formulations. Upregulation of TH-1 helper cells and their actions with interleukins like IL-2, IL-12, and gamma IFN or antibodies to IL-4 and IL-10 may augment potently pathogen and tumor resistance. Similarly, transfection of tumor target cells with genes for IL-2, IL-12, gamma IFN, etc., offers novel vaccine treatment approaches. Finally, "thymomimetic" peptides like thymosin alpha 1 or drugs like levamisole or isoprinosine alone or in conjunction with interleukins may augment TH-1 and DTH responses. These approaches are seeing increasing emphasis in new treatment strategies for cancer and infections like HIV.

The role of TNF-alpha in T-cell-mediated inflammation depends on the Th1/Th2 cytokine balance

The role of tumour necrosis factor-alpha (TNF-alpha) in tuberculosis is paradoxical because although there is much evidence for a protective role, there is also evidence that it plays a part in the tissue damage that characterizes human disease. We have shown previously that TNF-alpha frequently induces necrosis when injected into sites undergoing delayed-type hypersensitivity (DTH) responses to mycobacterial antigen. This is dependent on CD4+ T cells. However the presence of this sensitivity to TNF-alpha-induced necrosis depended on the immunization protocol. We have tested the hypothesis that sensitivity to TNF-alpha depends on the cytokine profile of the induced T-cell response. All subcutaneous doses of mycobacterial immunogen used (10(7) to 10(9) organisms) primed spleen cells so that they secreted interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) when cultured in vitro with soluble antigen. However priming for production of IL-4 was dose dependent as in other systems, and was produced at all times from 7 to 30 days after immunization with 10(9) organisms. Time-course studies over 30 days showed that sensitivity to TNF-alpha was found in DTH sites of animals primed for IL-4 and IFN-gamma production, but not in animals primed only for the Th1 cytokines. We suggest therefore that the paradoxical role of TNF-alpha can be resolved. In 'pure' Th1 responses it may act as an additional macrophage-activating factor. In mixed Th1 + Th2 or Th0 responses it may cause tissue damage. This mixed pattern is characteristic of tuberculosis, and of the late stage of many chronic infections where elimination of the infecting organism is failing, and chronic tissue damage is seen.

Different time course patterns of local expression of delayed-type hypersensitivity to sheep red blood cells in mice

The delayed-type hypersensitivity (DTH) reaction, a peripheral expression of cell-mediated immunity is still a crucial in vivo immunological test. Nevertheless, the biological significance of its time course remains unclear. Thus, an exhaustive study of DTH was undertaken in mice immunized with increasing doses of sheep red blood cells (SRBC) inoculated intravenously (iv) or subcutaneously. The results showed that overall DTH reactions peaked at 18 hr except in mice iv immunized with the lowest doses (10(5) and 10(6)) and elicited at Day 4. The protracted DTH reaction was shown to be associated with an histological picture of tuberculin-type reaction. A part of the 18-hr DTH reaction is mediated by serum in mice inoculated with large doses of SRBC; nevertheless, numeration by limiting dilution analysis of circulating DTH cells showed that the frequency of these cells correlates with the 18-hr DTH level. The protracted DTH shown at 42 and 48 hr, 4 days after immunization with 10(5) and 10(6) SRBC, could not be transferred in naive recipients with immune spleen cells; it was independent of the antigen life span and did not result from immunization modulation at the bone marrow level on recruitable cells.

Delayed-type hypersensitivity and protection in mice following immunization with Plasmodium berghei sporozoites

The measurement of footpad swelling (FPS) following the inoculation of sporozoite antigen (Ag) into the hind footpad (HFP) of outbred mice was used as an in vivo test of delayed-type hypersensitivity (DTH) to attenuated sporozoite immunization. An attempt was made to correlate DTH with protective antisporozoite immunity. The optimum time for testing DTH following a single intravenous immunization was four days. The optimum sensitizing dose was 1 x 10(5) attenuated sporozoites. A single immunization gave a greater FPS than multiple immunizations. Mice immunized with irradiation-attenuated sporozoites could be protected from a lethal challenge with nonattenuated sporozoites. The FPS response to mosquito debris Ag was minimal in mice sensitized by bites from infected mosquitos. Nude mice failed to develop an FPS response and could not mount a protective immunity with attenuated sporozoites. However, splenectomized mice did have an FPS response following sensitization. Mice infected with blood-stage parasites had negligible FPS response to sporozoite Ag. The FPS response to sporozoite Ag proved to be a correlate of DTH in mice sensitized with sporozoites.

Time course and histological differences between sheep red blood cells and tuberculin DTH reactions in mice

Delayed-type hypersensitivity (DTH) reactions induced with sheep red blood cells (1 X 10(8) SRBC/mouse) or with attenuated viable Mycobacterium bovis (4 X 10(6) BCG/mouse) inoculated subcutaneously and elicited, respectively, with SRBC or protein-purified derivative (PPD), were studied regularly in separate groups of outbred mice and compared during a period of one year following immunization. The present report shows the existence of two distinct types of DTH reactions. The SRBC type consists of a reaction which peaks consistently at 18 h, reaches a maximum 4 days after immunization, and decreases progressively until the fourth month. This local reaction, mediated by specific committed T cells as demonstrated by adoptive transfer experiments, was shown to consist mainly of a polymorphonuclear leukocyte infiltration. The PPD type consists of a local reaction which presents a different time course, the peak shifting from 18 to 42 h during the first two months after immunization, and which persists unchanged over a year after immunization. This second type of DTH reaction consisted of an early phase of polymorphonuclear infiltration followed by an increased number of mononuclear cells. Evidence is also given that the differences in the expression of these two types of DTH reactions depended neither upon the physical characteristics of the two antigens used for elicitation nor upon the nonspecific environmental modulating activity of BCG, since soluble SRBC protein and heat-killed BCG cells elicited the same distinct types, and the two distinct DTH reaction types could be elicited in mice immunized with both BCG and SRBC.

Effect of Bacillus Calmette-Guérin infection on delayed footpad reaction to Listeria monocytogenes

The role of peritoneal macrophages induced by Bacillus Calmette-Guérin (BCG) in the induction of immune responses to Listeria monocytogenes was studied in mice. The peritoneal macrophages from mice treated with BCG 14 days previously contained a high proportion of Ia-bearing macrophages (approximately 56%) and the cells showed not only a high level of listericidal activity but also a strong ability for presentation of listerial antigen to Listeria-immune T cells. An intraperitoneal inoculation with a low dose of Listeria, which can induce the maximal level of delayed footpad reaction (DFR) and positive migration inhibitory activity of macrophages in untreated mice, did not induce a detectable level of such responses in BCG-treated mice. The bacterial growth at an early stage of infection was suppressed by scavenger macrophages in these mice. On the other hand, BCG-treated mice showed the early development of DFR and macrophage migration inhibitory activity after an inoculation with a high dose of Listeria. It is revealed in transfer experiments that Listeria-pulsed peritoneal exudate cells induced by BCG elicited the highest level of DFR and positive migration inhibition of macrophages in normal mice at the earlier period of injection compared with Listeria-pulsed resident peritoneal cells. These results suggested that the increased activities of macrophages acting as scavenger cells and as antigen-presenting cells play important roles in the modification of immune responses to Listeria in BCG-treated mice.

The immunomodulatory effect of yeast glucan on delayed hypersensitivity

The effect of yeast beta-1, 3-glucan as an immunopotentiator of delayed type-hypersensitivity reactions (DHR) was studied. Delayed-type-hypersensitivity reactions in mice sensitized intraperitoneally (IP) with sheep red blood cells (SRBC) and pretreated three days previously with glucan given IP were significantly increased. However, mice sensitized IP with SRBC three days after the subcutaneous (SC) administration of glucan showed depressed DHR. Glucan given at the same site but not at distance strongly potentiated the DHR induced by SC sensitization with SRBC. Subcutaneous injection of glucan and SRBC given together also resulted in a sustained DHR which persisted twelve days after sensitization when DHR of control mice had waned.

Allergic hypersensitivity to the insecticide malathion in BALB/c mice

The widely used insecticide malathion (diethylmercaptosuccinate, S ester with O,O-dimethylphosphorodithioate) has been reported to cause allergic responses in some exposed people and in guinea pigs. In this study, IgE antibody-mediated and cell-mediated hypersensitivity to malathion was evaluated in female BALB/c mice. To elicit malathion-specific antibodies of the IgE class, a conjugate of the anhydride of the diacid metabolite of malathion (MMA) with keyhole limpet hemocyanin was administered ip with aluminum hydroxide as adjuvant. Sera collected following three sequential sensitizations were tested for specific IgE with the passive cutaneous anaphylaxis (PCA) test in Sprague-Dawley rats. MMA coupled to bovine serum albumin was used as the challenge antigen. Specific IgE was produced following the second and third sensitization in the mice receiving 10 and 100 micrograms of conjugate and following the third sensitization in the mice receiving 1 microgram of conjugate. A paper radioallergosorbent test (PRAST) was as sensitive as and showed a good correlation with the PCA assay for samples analyzed by both procedures. Malathion applied epicutaneously on 2 days or over 4 weeks failed to elicit delayed-type hypersensitivity as determined by change in ear thickness, 5-[125I]iodo-2'-deoxyuridine incorporation in the ear, and histology of the ear following ear challenge, with or without pretreatment of the mice with cyclophosphamide. MMA-specific IgE antibodies were not detected by the PCA test in the serum of mice treated epicutaneously for 4 weeks.

Delayed hypersensitivity and migration inhibition in two lines of mice genetically selected for high or low responsiveness to phytohemagglutinin

Delayed-type hypersensitivity (DTH) and cell migration inhibition (MI) were studied in two lines of mice genetically selected for the high (Hi/PHA) or low (Lo/PHA) in vitro response of their lymphoid cells to phytochemagglutinin (PHA). A rapid photoelectric procedure for reading cell migrations enabled the study of MI over a wide range (10 log) of antigen concentrations in vitro. Hi/PHA mice required immunization with a 10 times higher dose of ovalbumin (OVA) in Freund's complete adjuvant (FCA) than Lo/PHA mice for a comparable response in DTH (footpad swelling) and MI of their induced peritoneal exudate cells (PEC). Lo/PHA spleen showed marked bizonal MI on Day 5 after immunization with low doses (0.1 and 0.5 micrograms) of OVA in FCA, one peak being obtained in presence of in vitro concentrations of 10(-3) or 10(-2) micrograms/ml OVA and another peak at 1 or 10 micrograms/ml, whereas Hi/PHA spleen showed stimulation of migration. In contrast, MI in Lo/PHA spleen failed to persist beyond Day 19, whereas it appeared progressively in Hi/PHA spleen, being maximal by Day 27. Low-zone inhibition in Hi/PHA spleen and PEC was lacking or poor even after immunization with higher doses of OVA in FCA. The implications of these findings are discussed.

Development of immunity against Listeria monocytogenes in athymic nude versus neonatally thymectomized mice

The thymus requirement for the development of immunological responsiveness was determined by estimation of immune responses raised to Listeria monocytogenes in athymic nude, neonatally thymectomized, and sham-operated mice at 6 weeks of age. Not only sham-operated mice, but also neonatally thymectomized mice could completely eliminate the bacteria from the spleen and liver, while athymic nude mice could not eliminate them and showed a persistent form of infection. A strong delayed footpad reaction and acquired cellular resistance could be raised in neonatally thymectomized mice just as well as in sham-operated mice, but not in athymic nude mice. The delayed footpad reaction could be induced in neonatally thymectomized mice without an accompanying ability to inhibit macrophage migration. These results suggest that T cells responsible for immunity against listerial infection require the presence of the thymus for only a very short period in their development.

Delayed-type hypersensitivity response in mice to Treponema pallidum

C3H/HeJ mice which had been primed with either virulent or killed T. pallidum were studied for in vivo delayed-type hypersensitivity (DTH) responses to T. pallidum following local footpad challenge. Mice sustaining a chronic infection of 5 months duration failed to develop a DTH to treponemal antigens, whereas priming by a single intravenous injection with killed organisms resulted in a significant DTH response in mice when challenged 5 days later. Treatment of mice prior to priming with a single sublethal dose of cyclophosphamide (100 mg/kg body weight) not only failed to potentiate T. pallidum-DTH, but abrogated the response observed in untreated primed animals.

Allergic hypersensitivity to the herbicide 2,4-D in BALB/c mice

Following several reports of human allergic hypersensitivity, the ability of 2,4-D (2,4-dichlorophenoxyacetic acid) to elicit 2,4-D-specific IgE antibodies and delayed-type hypersensitivity in BALB/c mice was studied. 2,4-D-specific IgE antibodies were detected in mouse sera following the second intraperitoneal immunization with 1, 10, or 100 micrograms 2,4-D-keyhold limpet hemocyanin conjugate with aluminum hydroxide adjuvant. Specific IgE was determined with the rat passive cutaneous anaphylaxis test using a conjugate of 2,4-D with bovine serum albumin for challenge. The highest antibody titers and a measurable response in all mice were seen in the group that received 1 microgram of 2,4-D conjugate. Dinitrophenyl-specific IgE was measured at all intervals examined in mice immunized with a dinitrophenyl-keyhole limpet hemocyanin conjugate. 2,4-D applied epicutaneously on 2 d or over 4 wk failed to elicit delayed-type hypersensitivity as measured by change in ear thickness, incorporation of 5-[125I]iodo-2'-deoxyuridine, or histology following challenge on the ear. No 2,4-D-specific IgE antibodies were detected in serum during the 4-wk sensitization period. Similar treatment with a known sensitizer, dinitrofluorobenzene, produced delayed hypersensitivity. Following 4 wk of dosing, low titers of dinitrophenyl-specific IgE antibodies were elicited.

Regulation of contact allergy in the B cell--deficient mouse

We have examined the obligate role of B cells in the regulation of allergic contact dermatitis. Our model is ACD in mice made B cell deficient by the chronic administration from birth of a goat antisera to mouse IgM. The following ACD phenomena are well demonstrated in these mice: (1) acquisition and expression of ACD, (2) spontaneous waning of ACD soon after sensitization, (3) immunological tolerance induced by pretreatment with either parenteral hapten or haptenated spleen cells, (4) immunopotentiation by means of either cyclophosphamide or the local administration of a suspension of killed C. parvum (P. acnes), (5) the flare-up of previous test sites following the local administration of parenteral allergen, and (6) acquisition and expression of photo-ACD. We conclude that B cell participation is not required for these ACD phenomena, although an optional or subsidiary function for B regulatory cells is not excluded.

Immunomodulation with P40, an insoluble delipidated fraction of Corynebacterium granulosum. I.--Immune response to sheep red blood cells

The immunological responses to sheep red blood cells (SRBC) were evaluated in mice in order to study the immunomodulating effects of an insoluble fraction of Corynebacterium granulosum, designated P40. A single intravenous (IV) injection of 50 micrograms or more of P40 was able to stimulate the reticulo-endothelial system, as measured by the spleen index. A single IV injection of 250 micrograms of P40, given seven days prior to IV sensitization of groups of mice with varying doses of SRBC, was able to amplify both humoral and cellular immune responses. Lower doses of P40 given subcutaneously (SC) were able to potentiate delayed-type hypersensitivity (DTH) to SRBC. Potentiation depends on the route, dose and time of the P40 injection in relation to the time and route of sensitization. A bimodal activity of P40 was observed: one peak was noted with SRBC were mixed with P40, and a second peak occurred when P40 was injected at the same site four to five days prior to immunization. Maximal potentiation was achieved when SRBC were introduced SC together with 5 micrograms of P40. DTH reached a higher level in animals immunized under the influence of P40; however, the kinetics of the development and decay of DTH were the same in treated and non-treated mice. Immunopotentiation was demonstrated by passive transfer: using the same number of spleen cells from treated or non-treated immune mice, higher DTH reactions were observed in normal recipients when they received spleen cells from P40-treated donor mice. Immunopotentiation seemed to act by increasing the number of committed lymphocytes and not by augmenting the number of accessory cells, since adoptive transfer of DTH by immune cells was not different in normal or P40-treated recipients.

Decreased phospholipase A2 activity and prostaglandin biosynthesis in Bacillus Calmette-Guérin-activated alveolar macrophages

Alveolar macrophages from normal and BCG-infected rabbits were labelled with [14C]arachidonate and its metabolites were measured. It was found that production of both prostaglandins and 12-hydroxyeicosatetraenoic acid was diminished markedly in BCG-primed macrophages. This decrease was due partly to a depression in cyclooxygenase and lipoxygenase activity, but mainly to a decrease in arachidonic acid release, probably due to a suppression in phospholipase A2 activity. This is indicated by a consistent depression of this enzyme activity in BCG macrophage homogenates at a wide pH range, suggesting that both lysosomal an non-lysosomal phospholipases are suppressed in BCG macrophages. However, intracellular lysosomal acid phosphatase and its release were increased markedly in BCG-primed macrophages. Our previous studies have shown a close relationship between lysosomal acid hydrolase release and production of arachidonate-prostaglandins in normal macrophages. The present study shows that in activated macrophages primed by BCG, different mechanisms are operative in the control of synthesis and release of lysosomal acid hydrolases and of the phospholipase for prostaglandin production.

Transfer of delayed hypersensitivity in the chicken

Delayed hypersensitivity (DH) can be transferred in FP and SC chickens with 1 x 10(8) spleen or peripheral blood cells from donors exhibiting moderate to strong DH reactions. Increasing the spleen cells dose from 1 to 4 x 10(8) per recipient had no marked enhancing effect on the results. Spleen cells from agammaglobulinemic donors were also shown to transfer DH reactions.

Suppression of BCG cell wall induced delayed-type hypersensitivity by BCG pre-treatment. I. Induction of adherent suppressor cells by live BCG injection and their characterization

Previous injections of live Bacillus Calmette-Guérin (BCG) in mice produced a suppression of delayed-type hypersensitivity (DTH) induced by oil-treated BCG cell walls (CW). This phenomenon was analysed by the macrophage migration inhibition (MI) test in which peritoneal exudate cells (PEC) from live BCG-injected mice were mixed with PEC from BCG CW-immunized mice, with the result that the former cells suppressed the MI activity in the latter. We considered the Mi test to be a reliable method for demonstrating the existence of suppressor cells induced by the injection of live BCG. Moreover, we found that the adherent cells of PEC possessed a suppressive effect which was retained even after treatment with either anti-mouse Ig or anti-brain associated theta (BA theta) antigen; that the PEC from mice injected with live BCG on at least the 12th day before cell harvesting showed the suppression; and that the suppression operated across the H-2 barrier.

Absence of correlation between delayed-type hypersensitivity and protection in experimental systemic candidiasis in immunized mice

We found that in mice which had been immunized intraperitoneally with 2 x 10(8) heat-killed Candida albicans cells there was a striking temporal relationship between resistance to systemic challenge with 10(6) living C. albicans cells and a number of measurable cellular parameters of the host response. These included the emergence of delayed-type hypersensitivity and the development of granulocytosis. Since it had been shown in previous work that granulocytosis was associated with an increase in resistance when nonspecific immunostimulation was used, we performed experiments to induce delayed-type hypersensitivity without any measurable modification of the granulocyte population. Adoptive transfer of delayed-type hypersensitivity with spleen cells from immune and resistant donor mice did not produce any increase in resistance in normal recipients. When separate groups of mice were immunized intraperitoneally or subcutaneously with varying doses of heat-killed C. albicans, we found that doses of less than 10(8) cells did induce significant delayed-type hypersensitivity without any increase in granulocytosis. In such mice, as well as in animals pretreated with immunomodulators before immunization with heat-killed C. albicans, the presence of cell-mediated immunity, as measured by the delayed-type hypersensitivity test, was not associated with an increase in resistance against systemic candidiasis. On the contrary, the results suggested that cell-mediated immunity was associated with an increase in the susceptibility of these mice. The same effect on candidiasis susceptibility was observed when animals were immunized with heat-killed filamentous C. albicans.

Enhanced elimination of Listeria monocytogenes at the site of delayed footpad reaction

The protective activity against a challenge infection with Listeria monocytogenes was investigated at the site of a delayed footpad reaction in mice immunized with viable or killed listeria. Delayed footpad reactivity was induced only in mice immunized with viable bacteria. Rapid and marked elimination of challenge bacteria was observed only at the site of reaction in mice immunized with viable bacteria but not in mice immunized with killed bacteria. Macrophage migration inhibitory activity was observed equally in both groups of mice. These results suggest that the delayed footpad reaction contributes directly to the elimination of bacteria irrespective of macrophage migration inhibitory activity.

Comparability of delayed hypersensitivity in various rodents. II. Jones-Mote type hypersensitivity in guinea-pigs immunized with sheep erythrocytes and its modification by cyclophosphamide or BCG pre-treatment

Guinea-pigs were immunized via footpads with sheep red blood cells (SRBC) in saline. Histological examination of erythematous skin reaction was performed and effects of cyclophosphamide (CY) or BCG pre-treatment on the skin reaction were examined. Delayed-in-onset erythematous skin reaction accompanied by substantial basophil infiltration was elicited in guinea-pigs immunized with SRBC in saline. The erythema was augmented in size by CY which was injected 2 days before immunization. The reaction may be comparable to Jones-Mote type. In BCG pre-treated guinea-pigs, basophil infiltration at the skin reaction sites was reduced in number, but significant inhibition of macrophage migration was not detected in the presence of SRBC antigen. The reaction may be intermediate between Jones-Mote and the tuberculin type. Comparability of delayed skin reactions in guinea-pigs and delayed footpad reactions in mice or hamsters against SRBC is discussed.

The follow-up study of skin reactivity to recall antigens and E- and EAC-RFC profiles in blood in asbestos workers

We have determined cutaneous DTH reactions to SK-SD and PPD and peripheral blood lymphocyte profiles in a group of asbestos workers in two consecutive surveys. It was found that asbestosis and, to a lesser extent, the presence of ANA are significantly correlated with the lack of response to the above antigens. 83% of asbestos workers when tested at a 4 year interval fell into the same two categories of responsiveness (lack of response or response at least to one antigen). The asbestosis cases had lower total lymphocyte count as well as proportions and absolute number of E-RFC as compared to asbestos workers without asbestosis and/or ANA. Furthermore, the latter group showed the lower percentages and absolute number of E-RFC than the matched controls. The presence of ANA is also correlated with lower proportions of E-RFC. However, this is related at least in part to asbestosis.

Role of antigen-presenting cells in the development and persistence of contact hypersensitivity

Three outcomes pertinent to contact sensitivity (CS) follow immunization with various forms of trinitrophenylated (TNP) substrates: (a) specific immunological unresponsiveness for CS is induced when immunization favors activation of splenic suppressor cells. This state is achieved by intravenous injection of trinitrophenyl-conjugated to various types of cells, such as peritoneal exudate cells (PEC). (b) A short-lived or evanescent form of CS is induced when immunization reduces activation of the suppressor circuit. This can be achieved by subcutaneous immunization with trinitrophenyl conjugated to syngeneic PEC, by pretreatment with cyclophosphamide to diminish suppression before intravenous immunization, or by altering the mode of antigen presentation by using TNP-substrate that has undergone phagocytosis. (c) A long-lived form of CS is induced when trinitrophenyl is presented to the immune system on skin cells either by contact skin painting with reactive trinitrophenyl, or by subcutaneous, or even intravenous injection of trinitrophenyl-conjugated epidermal cells. In fact, trinitrophenyl-conjugated epidermal cells induced CS even when the suppressor circuit was activated by intravenous coadministration of TNP-PEC. This implies that antigen presentation on epidermal cells induces sensitized cells that are relatively resistant to suppression. The cell type(s) in the skin that are primarily responsible for this potent form of antigen presentation are most likely Langerhans cells, because they can be concentrated by virtue of their Fc receptors and they are Ia positive. Thus, both the anatomical site where antigen is first encountered by the immune apparatus, as well as the nature of the cells which present the antigen, determine whether a CS response will ensue, as well as whether it will be evanescent or long-lasting.

Kinetics of different specific immunological parameters after rabies vaccination in mice

A significant protection to an intracerebral challenge of 70 mean lethal doses of a standard live rabies virus strain was obtained in BCG-pretreated mice or in normal mice which had been immunized with a single subcutaneous injection of a beta-propiolactone-inactivated rabies vaccine. Concomitantly, levels of delayed-type hypersensitivity (measured in vivo by the footpad test) and serum-neutralizing activity were evaluated at various times after immunization. All immune criteria were significantly augmented in the BCG-pretreated, rabies-immune mice as compared to normal, rabies-immune mice. However, peak levels of protection, delayed-type hypersensitivity, and serum-neutralizing activity did not occur at the same times. For instance, in the BCG-pretreated, rabies-immune mice, delayed-type hypersensitivity peaked on day 7, protection peaked on day 21, and serum-neutralizing activity peaked on day 60. In BCG-pretreated mice, which did not receive the rabies vaccine, positive delayed-type hypersensitivity, some protection, and serum neutralizing activity were observed 4 to 5 weeks after BCG pretreatment. The possible relationships between specific and nonspecific immunity provoked by rabies virus antigens, tissue culture cell-associated antigens (derived from the bovine fetal kidney cells in which the rabies virus was grown, and BCG are discussed.

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.

Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. I. Production and characterization as to function and phenotype

T lymphocytes which mediate DTH reactions to sheep red blood cells (SRBC) in mice enter casein-induced peritoneal exudates from which they can be recovered and assayed in a passive transfer system. Peritoneal exudates need not contain specific antigen for inducement of T-cell immigration. The amount (or biological activity) of DTH-transferring peritoneal exudate lymphocytes is enhanced by the previous use of immune modulating agents, such as cyclophosphamide (Cy) (200 mg/kg 2 days prior to sensitization), or BCG (10(7) live organisms i.v. 14 days prior to sensitization). SRBC-specific peritoneal exudate lymphocytes phenotypically are Thy 1+ and Ly 1+, 2-. In vivo, peritoneal exudate T cells from Cymodulated donors persist in circulation for a short period only and are subject to the suppressive mechanisms acting in anergic mice. Cells from BCG-plus-Cy-modulated donors, on the other hand, persist in circulation for a longer period and appear to be less susceptible to immune suppression.

Cellular antimicrobial immunity

Acquired resistance to infectious disease may be expressed by a predominantly humoral or a cellular mechanism or, more frequently, by a combination of the two. The cellular interactions which are responsible for the induction of the immune response in the skin, lung, intestinal mucosa, genitourinary tract, conjunctiva, and peritoneal cavity are discussed and the role of living or dead vaccines in the induction of acquired resistance is outlined. The host response involves three different cell types: the phagocytic cell (polymorphs or macrophages), the thymus-dependent (T) lymphocyte, and the thymus-independent (B) lymphocyte-plasma cell line. The normal unstimulated phagocytic cell is capable of killing most nonpathogenic bacteria that gain entry to the tissues. However, the presence of opsonic antibodies and activated macrophages is required to eliminate the pathogenic intracellular parasites. Such immunological activation involves the presence of sensitized T-lymphocytes in the lesion. The cellular response is also characterized by the simultaneous development of a state of delayed-type hypersensitivity (DTH), along with the antimicrobial CMI response. A rising humoral response normally develops subsequently. Killed bacterial cells (except when incorporated into Freund's complete adjuvant) induce the humoral response without the CMI reaction so that such vaccines are not able to fully protect the host against the naturally acquired disease. With the development of cell fractionation methods as well as the identification of distinctive cell surface markers, suspensions of B- and T-cells and macrophages can now be prepared for use in increasingly sophisticated transfer and reconstitution studies. The role of the different cell types in the expression of humoral and cellular immunity has been determined, and the effect of various immunopotentiating and immunosuppressive regimens on the immune system as a whole has been evaluated quantitatively. These studies have led to an appreciation of the role played by suppressor B- and T-cells in the interplay of both humoral and cellular components of the host defense system during the development of immune tolerance, desensitization, anergy, autoimmunity, and the expression of an anamnestic immune response following reinfection.

Delayed-type hypersensitivity to rabies virus in mice: assay of active or passive sensitization by the footpad test

With a purified beta-propiolactone-inactivated rabies virus, a significant increase in footpad swelling was elicited in normal or in BCG-pretreated mice after immunization with varying doses of rabies vaccine. These footpad reactions were shown to peak at 24 h and to be associated with an infiltration of newly formed blood monocytes demonstrated by histology and [125I]deoxyuridine labeling. A relationship between the lymphoproliferation and the degree of sensitization is described, and the susceptibility to cyclophosphamide treatment is also examined. Adoptive transfer of specific reactivity to normal recipient mice with immune lymphoid cells, but not with immune serum, was demonstrated, and the results represent another argument for a cell-mediated immunological mechanism.