The compartmentalization of antigen-reactive lymphocytes in desensitized guinea pigs

Effect of a recent injection of purified protein derivative on diagnostic tests for tuberculosis in cattle infected with Mycobacterium bovis

The intradermal injection of avian and bovine purified protein derivative into 15 Mycobacterium bovis-infected cattle reduced the capacity of a second single intradermal comparative tuberculin test carried out seven days later to predict accurately the animals' infection status (P < 0.001). In vitro lymphyocyte blastogenesis was also reduced (P < 0.05) but the in vitro production of interferon-gamma was unaffected.

Haematological changes associated with miliary tuberculosis of the bone marrow

The peripheral blood and bone marrow findings in 25 patients found to have tuberculous granulomata on bone marrow examination were examined to determine whether specific haematological findings are associated with tuberculous infiltration of the bone marrow. All the patients had one abnormality or more on their full blood count. The presence of a peripheral lymphopaenia was the single factor common to all 25 patients studied. The peripheral lymphopaenia was only associated with bone marrow lymphopaenia in 14% of patients. Other findings of note were an association of peripheral monocytopaenia and absence of giant cells in the granulomata, and decreased iron stores in almost a third of the total number of patients. The relevance of the lymphopaenia, monocytopaenia and decreased iron stores are discussed and we propose that the absence of a peripheral lymphopaenia makes it very unlikely that there will be tuberculous localization in the bone marrow.

Desensitization of delayed-type hypersensitivity in mice: suppressive environment

The systemic injection of high doses of antigen into a preimmunized animal results in transient unresponsiveness of cell-mediated immune responses. This phenomenon is known as desensitization. Serum interleukin 2 (IL-2) activity was found transiently in desensitized mice at 3 h after the antigen challenge. These mice could not reveal antigen nonspecific delayed-type hypersensitivity (DTH) 1 d after the challenge. Specific suppression of DTH was observed at later stages. Sera from 3 h desensitized mice showed suppressive effects on DTH in preo immunized mice. Administration of recombinant IL-2 into preimmunized mice led to the failure of development of DTH to antigens. These observations suggest that IL-2 plays an important role in the suppressive environment.

Desensitization of delayed-type hypersensitivity in mice: possible involvement of interleukin 2-dependent regulatory mechanisms in desensitized mice

The systemic injection of high doses of antigen into a previously immunized animal results in a state of transient anergy with respect to cell-mediated immune responses. This phenomenon is known as desensitization. The results presented here demonstrated that serum interleukin 2 (IL-2) activity was found transiently in desensitized mice at early stage (3 hr after the challenge). Subsequently, these mice could not develop in vivo (footpad swelling) and in vitro (lymphocyte proliferation) manifestations of cell-mediated immune responses 1 day after the challenge. Antigen-nonspecific and specific suppression of IL-2 production was observed in desensitized mice. The serum from 3 hr-desensitized mice containing endogenous IL-2 activity showed a marked suppressive effect on IL-2 production. Exposure of lymph node cells to IL-2 was capable of inhibiting IL-2 production in vitro. Additionally, in vivo administration of exogenous IL-2 into preimmunized mice led to the failure of development of footpad responses to antigen. These results suggest that IL-2-dependent regulatory mechanisms of T cell-mediated immune responses play an important role in the immunosuppression of desensitized mice.

B-cell-mediated depression of the granulomatous response to BCG in mice

The depression of the granulomatous response to Mycobacterium bovis strain BCG in mice infected intravenously with 2 x 10(7) CFU of the microorganism turned out to be mediated by various types of cells arising at different times after infection. Anti-PPD B lymphocytes were found to play a major role at Day 1 after infection and to be no longer effective 4 days later. At this time the depression was mediated by anti-idiotype B lymphocytes, whereas T lymphocytes proved to be involved in later phases of the infectious process. These results show that B lymphocytes may be of critical importance in the regulation of cell-mediated immune reactions to this facultative intracellular parasite.

Presence of Mycobacterium leprae-reactive lymphocytes in lymph nodes of lepromatous leprosy patients

A critical problem in leprosy is the relative deficiency of antigen-specific T cell-mediated immunity. We were successful in detecting a significant response to viable M. leprae in mononuclear cells isolated from the lymph nodes of lepromatous leprosy patients in contrast to the apparent M. leprae-specific energy seen in the peripheral blood. This observation suggests that antigen-reactive lymphocytes are generated in the lymph nodes of lepromatous patients but the inability to detect them in the circulation may be due either to a different processing and presentation of mycobacterial antigens within the peripheral blood and lymph node compartments or to a selective sequestration of lymphocytes within the lymph node.

T4 lymphopenia in human tuberculosis

Lymphocyte subpopulations in vitro in 13 patients with bacteriologically-proven tuberculosis and 12 matched controls, by immunofluorescence using monoclonal antibodies have been studied. Active tuberculosis was associated with significant reductions in absolute numbers of total T (Leu 4 or 1+), T4 (Leu 3a+) and B (Leu 12+) lymphocytes, but there were no significant differences in total T8 (Leu 2a+) counts. In two patients, T4-lymphopenia was sufficiently profound to cause reversal of T4: T8 ratio (less than 1.2). These changes were not related to the radiological extent of the disease or size of the Mantoux reaction. Normal ranges for the different classes of lymphocytes were readily restored by chemotherapy.

Cell mediated immunity to liver fluke antigens during experimental Fasciola hepatica infection of cattle

Cell mediated immunity (CMI) to Fasciola hepatica antigens was detected by lymphocyte proliferation and interleukin-2 (IL-2) production tests in cattle during the first 4 weeks following liver fluke infection. From the fifth week of infection onwards peripheral blood lymphocytes were unresponsive to fluke antigens by these in vitro tests. Investigations into the cause of this unresponsiveness found no evidence to suggest a selective loss of the IL-2 producing lymphocyte sub-population or that macrophages were responsible for the suppression or that antigen responsive cells were being sequestered in the spleen and mesenteric lymph nodes. Tests carried out on culture supernatants demonstrated the production during this unresponsive period of factors capable of suppressing in vitro responses to PHA. Although further tests failed to show antigen specific suppressor factors the presence of MHC restricted suppressor factors could not be ruled out. The early and transient appearance of CMI during F. hepatica infection of cattle indicates that delayed type hypersensitivity is unlikely to be important in protective immunity in cattle.

Deficient immune interferon production in tuberculosis

Production of interferon (IFN)-alpha and -gamma by peripheral blood mononuclear cells (PBMC) were studied in 28 patients with active tuberculosis and 28 healthy control subjects matched for age, sex, ethnic origin and diet. No significant differences were found between patients and matched controls in mean titres of IFN-alpha induced by Newcastle disease virus, IFN-gamma induced by staphylococcal enterotoxin A with tetrahydrophorbyl acetate, and IFN-gamma induced by purified protein derivative (PPD). However, a subset of nine out of 25 tuberculosis patients tested produced low titres (less than 100 u/ml) of IFN-gamma in response to PBMC stimulation with PPD. In comparison to other patients, this group was characterized by lower IFN-alpha and IFN-gamma responses to virus and mitogens respectively, relative anergy to tuberculin skin testing, depressed in vitro PBMC proliferative responses to PPD, and neutrophil leucocytosis. In all nine patients effective chemotherapy restored cutaneous reactivity, PBMC proliferative responses, neutrophil counts and IFN-alpha responses to virus by 6 months, and also IFN-gamma responses to PPD in one patient re-tested.

Passive transfer of tuberculin sensitivity from anergic mice

Mice heavily infected with Mycobacterium bovis BCG rapidly became anergic to cutaneous injection with tuberculin. Evidence is presented suggesting that this anergy reflects an adaptive physiological change within the host in which antigen-reactive Thy-1.2+ cells become sequestered in central lymphoid tissues, with a concomitant reduction in the circulating pool. No evidence could be provided to support the suggestion that anergy was a consequence of an acquired immunosuppressive mechanism.

In vitro changes in cell mediated immunity following tuberculin skin testing in humans

Tuberculin skin testing with purified protein derivative (PPD) was found to induce alterations of in vitro measures of cell mediated immunity. T lymphopenia with proportionate decreases of TM and TG cell numbers were observed two days after skin testing. A relative augmentation of TM cells was demonstrated after one week. Peripheral blood mononuclear cells from negative skin responders had normal in vitro reactivity to PPD stimulation suggesting a cutaneous abberation in these individuals. Macrophage dependent depressed PHA reactivity of mononuclear cells was demonstrated two days after skin testing. No change in natural killer cell cytotoxicity was observed. Cytotoxicity was positively correlated to the number of TG cells in the assay.

Alterations in T lymphocytes and T-lymphocyte subpopulations in patients with syphilis

The distribution of T-lymphocyte subpopulations was studied in 34 patients with primary or secondary syphilis before and after treatment. An absolute and relative T lymphopenia was found in all patients. In primary syphilis the concentration of helper cells--T cells with Fc receptors for IgM (T mu)--was low whereas in secondary syphilis the suppressor cell concentration--T cells with Fc receptors for IgG (T gamma)--was reduced. Using lymphocytes from healthy subjects this could be imitated in vitro by the addition of serum from patients with secondary syphilis. In many autoimmune diseases a low concentration of T gamma may be a primary factor in the production of autoantibodies. The occurrence of similar changes in patients with secondary syphilis, however, indicates that such fluctuations in the T-cell subpopulations may take place during a strong immune response.

Subpopulations of T lymphocytes and non-specific suppressor cell activity in patients with atopic dermatitis

Thirty-five adult persons with moderate to severe atopic dermatitis and increased levels of IgE in serum were studied for the presence of Fc-IgG (T gamma) and Fc-IgM (T mu) receptor-carrying T lymphocytes in peripheral blood. When T lymphocytes from the patient were kept in vitro cultures a reduced expansion of the Fc-IgG receptors was found after 24 hr of incubation, but not after 48 hr of incubation. No difference was observed concerning Fc-IgM-carrying T lymphocytes. In 19 patients we studied Con A-induced suppressor activity of blood lymphocytes using autologous PHA-stimulated lymphocytes as target cells. Following stimulation with Con A, 1 microgram/ml, for 2 and 4 days, lymphocytes from atopic patients had a reduced non-specific suppressor activity in vitro. If however, the concentration of Con A was increased to 10 microgram/ml, then lymphocytes from atopic patients exhibited a normal suppressor activity.

Properties of peritoneal exudate lymphocytes that mediate tuberculin delayed-type hypersensitivity and anti-tuberculosis immunity

Rats were immunized with living BCG and acute peritoneal exudates were induced on the ninth day of infection. The peritoneal exudate cells (PEC), that confer adoptive anti-tuberculosis immunity and tuberculin delayed-type hypersensitivity (DTH), were subject to velocity sedimentation analysis. It was found that the ability to confer immunity of DTH was limited to a population of cells that sedimented at a rate of 3-4 mm/h. This sedimentation rate corresponds to that of small lymphocytes. No significant immunological activity was detected in large lymphocytes that incorporate [3H]-thymidine in vitro, regardless of whether the exudates were obtained 14 to 24 h after induction of peritoneal inflammation. The failure of large lymphocytes to confer immunity and DTH was not due to adherent cells with suppressor activity, because removal of adherent cells failed to amplify the transfer of immunological activity by non-adherent cells. The persistence of the ability to express immunity and DTH in adoptively immunized rats was studied. There was no decay of adoptive immunity during a 4 week period following cell transfer, but there was a rapid reduction in the expression of DTH.

Selective suppression of granuloma formation and delayed hypersensitivity in rabbits

The relationship between dermal delayed hypersensitivity (DH) and granulomatous hypersensitivity was studied in rabbits sensitized with killed mycobacteria. Specific antigen challenge of sensitized animals resulted in extensive pulmonary granulomatous inflammation and induced suppression of both dermal DH and dermal granuloma formation. Whereas suppression of DH was concomitant with pulmonary granuloma formation, as is the case in a number of granulomatous diseases, a causal relationship between the two did not exist. Both DH and dermal granulomatous hypersensitivity were significantly suppressed whether or not the antigen challenge was of a granulomagenic (particulate) or nongranulomagenic (soluble) form. The data presented indicate that granulomatous hypersensitivity and DH are selectively suppressed with regard to different anatomical sites.

Local immune response to Mycobacterium lepraemurium in C3H and C57Bl/6 mice

Subcutaneous footpad inoculation of living M. lepraemurium (L.MLM) induced, in high responder C57Bl/6 mice, a local granulomatous reaction associated with the production of effector cells which stopped the multiplication of bacilli in the draining popliteal node with the concurrent development of 24--48 hr delayed type hypersensitivity (DTH). The thymus-dependent local reaction did not occur after the injection of heat-killed M. lepraemurium (HK.MLM) or after the inoculation of L.MLM in nude mice. However, HK.MLM injection interfered with the onset of the local reaction and enhanced acid-fast bacteria (AFB) counts in the draining node. In low responder C3H mice, L.MLM produced a local and delayed footpad swelling but no restriction of bacilli multiplication in the draining lymph node was observed. This unresponsiveness was not due to an overloading of the inoculum dose since doses ranging from 3 x 10(4) to 3 x 10(7) MLM did not produce any granulomatous local reaction as in C57Bl/6 mice. The injection of dead bacilli in the contralateral footpad of subcutaneously (s.c.) infected C3H mice revealed Arthus-like and 18--24 hr delayed reactions. When 10(6) L.MLM per mouse were injected intravenously (i.v.), systemic infection, measured in the spleen, was found to be less restricted in C57Bl/6 than in C3H mice. Moreover, in C57Bl/6 mice low doses of L.MLM injected i.v. delayed the local reaction at first, then enhanced footpad swelling and AFB counts in the draining nodes, indicating some acquired defect of peripheral immunity. When a high dose of L.MLM (2 x 10(8)/mouse) was injected i.v., C57Bl/6 mice died sooner than C3H mice, indicating certain discrepancies between local resistance and systemic susceptibility.

Immunological unresponsiveness during induction of experimental autoimmune orchitis in guinea-pigs: studies in vivo and in vitro

Groups of male and female guinea-pigs were immunized with homologous sperm derived from testis (TS) or epididyimis (ES) in Freund's complete adjuvant (FCA). In vivo investigations included skin tests at 2 weeks and development of aspermatogenesis (testis weight) at 4 weeks; in vitro assays were inhibition of migration of peritoneal exudate cells (PEC) and culture of blood leucocytes (lymphocyte transformation) at weekly intervals after immunization. Antigens used were heat-treated extracts of sperm used for immunization (BTS, BES); cells were also cultured simultaneously with PPD. Skin tests revealed anergy in males as compared with females: a larger quantity of antigen which caused partial unresponsiveness in females, caused profound unresponsiveness in males although the aspermatogenesis was less severe. In vitro tests also showed anergy during the active stages of the orchitis. This was non-specific for PEC (specific unresponsiveness was not excluded), but blood leucocytes showed only specific unresponsiveness (to BES). These and previous studies suggest that the unresponsiveness results from a desensitisation by sperm antigens released during the development of aspermatogenesis.

Migration inhibition factor study in Histoplasma capsulatum

Mice sublethally infected with viable Histoplasma capsulatum or immunized with merthiolate-killed yeast phase cells showed decreased mortality on subsequent challenge infection as compared to controls. Migration inhibition (MI) assays using peritoneal and spleen cells from immunized but unchallenged mice showed no parallel correlation with percent mortality. MI assay indices fluctuated without concomitant changes in resistance to challenge injection with live yeast phase cells. Viable vaccines induced greater resistance to challenge infection than killed cells, although both were comparable in sensitizing ability as measured by MI assay techniques with this mouse model.

Site of action of serum factors that block delayed-type hypersensitivity in mice

When mice have been rendered anergic by a large intravenous dose of sheep erythrocytes, their inability to mount a delayed-type hypersensitivity (DTH) reaction is not due to an absence of mediator cells, for these can be detected in the spleen by cell transfer. Nor is it due to disappearance of accessory cells (monocytes) from circulation. The serum of anergic mice contains blocking factors which are more abundant after absorption with antigen. Such factors are unable to inactivate the mediators of DTH in vitro, nor do they suppress a DTH reaction when introduced locally into the reaction site. They are active, however, when given intravenously to systemically sensitized mice, provided that the sensitized animal has an intact spleen. If the spleen has been removed or the recipients of sensitized cells have been treated with cyclophosphamide before cell transfer, blocking factors are no longer able to suppress a DTH reaction. Reasons are given for the belief that suppression of DTH in animals undergoing a vigorous antibody response is due to the diversion of reactive cells from circulation to undertake an alternative role in antibody formation in the spleen.

Relationship between delayed-type hypersensitivity and the progression of Mycobacterium lepraemurium infection

The relationship between the level of delayed-type hypersensitivity (DTH) and the progression of Mycobacterium lepraemurium infection was examined after inoculation of mice with 10(8) M. lepraemurium in the left hind footpad. The expression of DTH developed over the first 4 weeks of infection, remained high up to week 8, and then dropped to a low level at which it remained for 12 more weeks. The development of DTH was concordant with an initial swelling of the inoculated foot, the appearance of a mononuclear infiltrate at this site, and a prevention of any increase in the number of mycobacteria in this foot and in other tissues studied. A decay of DTH reactivity was associated with a progressive increase in the number of M. lepraemurium initially at the original site of inoculation and subsequently in all other tissues. Although the expression of DTH was lost, adoptive immunization experiments showed that a population of sensitized lymphocytes persisted within host. Further experimentation offered evidence to suggest that the level of systemic antigen may be in part responsible for the loss of DTH reactivity.

Lymphocyte migratory pathways in adjuvant disease. I. Distribution of 51Cr-labeled thoracic duct lymph-borne

Evidence for selective extravasation of thoracic duct lymph-borne cells, derived from rats with adjuvant disease, within joints of normal or adjuvant arthritic recipients was sough by adoptive transfer of radiolabeled cells. Control studies were carried out in parallel using thoracic ducts cells from normal donors. No increased homing of lymph-borne cells to inflamed portions of the limbs was detected when cells from adjuvant arthritic donors were compared with those of normal controls. Inflammatory changes, ie, adjuvant-induced disease, in the recipient produced a significant nonspecific enhancement of extravasation; cells from normal and adjuvant arthritic donors responded equally well. One difference in migratory behavior between lymph-borne cells from adjuvant arthritic and normal animals was the increased ability of the former to localize within certain lymph nodes. A possible association between this traffic and the development of chronic inflammatory processes within joints is discussed.

Mechanism of densensitization in DNCB-contact sensitive guinea pigs

Contact sensitivity to dinitrochlorobenzene (DNCB) in guinea pigs could be rapidly suppressed by intravenous injection of dinitrobenzene sulfonic acid sodium salt (DNBSO3). This suppression is transient and antigen-specific. Macrophages from desensitized animals are not inactivated as shown by their ability to react, both in vivo and in vitro to lymphokines produced in a separate system. Therefore, effector lymphocytes are considered the target for the desensitizing antigen. Using an adoptive transfer system it was demonstrated that effector lymphocytes are inactivated by a direct effect of the hapten. Since this inactivation can be reversed by trypsin treatment, a receptor blockade of effector lymphocytes is proposed as the mechanism of desensitization of DNCB-contact sensitive guinea pigs. This does not exclude the possibility that additional mechanisms such as suppressor cells, compartmentalization or endogenous proliferation of lymph node lymphocytes may play an additional role.

Preliminary evidence for the trapping of antigen-specific lymphocytes in the lymphoid tissue of 'anergic' tuberculosis patients

Lymphocyte-transformation responses to mycobacterial antigens have been studied, using paired blood and lymph node samples from 'normal' Ugandans, (hernia repairs or orthopaedic cases) or from patients with tuberculosis, Mycobacterium ulcerans infection, or injection abscesses. The results suggest that in some individuals, antigen reactive cells, although absent from the periphery, may be demonstrable in the lymph nodes. This phenomenon is most striking in skin-test negative tuberculosis patients.

Immune responses to mycobacteria in mice and men

This paper contains discussion of a number of mechanisms which may explain the suppression of the cell-mediated immune response during the phase of dissemination of mycobacterial infection in mice and men. However, it is not yet possible to evaluate the relative importance of these mechanisms, or even to say which are the causes and which are the consequences of that disseminaton.

Modulation of cellular-immune responses in vivo and in vitro by histamine receptor-bearing lymphocytes

Histamine, one of the mediators involved in the IgE-mediated reaction, was demonstrated to influence in vivo and in vitro components of cellular-immune reactions in orthochlorbenzoyl-bovine gamma globulin-immune guinea pigs. 10(-3) M histamine reduced by half the size of a delayed hypersensitivity skin test at 24 h. Inhibition of skin reactivity by histamine could be partially reversed by H-1 receptor antagonists such as chlorpheniramine and completely prevented by H-2 receptor antagonists such as burimamide. The histamine suppression of cutaneous delayed hypersensitivity could be accounted for in part by its inhibitory effect on certain lymphocyte responses including antigen-induced migration inhibitory factor (MIF) production and proliferation. At concentrations of 10(-3)-10(-5) M histamine reversibly inhibited MIF production and its action could be blocked by H-2 antagonists but not H-1 antagonists. Thus, lymphocytes bearing H-2 receptors modulate MIF production and probably lymphocyte proliferation as well. Histamine did not interfere with the macrophage response to preformed MIF. These studies indicate that immediate hypersensitivity reactions involving histamine release might influence the subsequent expression of cellular-immune reactions.

Mechanism of reappearance of contact sensitivity to DNCB in desensitized guinea pigs

The different immunologic activities of lymph node and spleen cells as compared to peritoneal exudate cells were studied in temporarily desensitized, DNCB-contact-sensitive guinea pigs. Lymph node (and spleen) lymphocytes: (a) transfer contact sensitivity to syngeneic recipients when harvested at the time of unresponsiveness; (b) are only temporarily inactivated in tolerant recipients by the desensitizing procedure; (c) enter the lymph node (or spleen) compartments in a higher proportion than peritoneal exudate cells; (d) are not susceptible to inactivation in vitro; and (e) are not permanently desensitized when released into the circulation by an intravenous injection of Bordetella pertussis vaccine. These results indicate that the resistance of primed lymph node cells to the desensitizing procedure may account for the reappearance of contact sensitivity in desensitized guinea pigs.

Antigen-binding T and B lymphocytes in sensitization and unresponsiveness to dinitrochlorobenzene (DNCB) contact sensitivity

The frequency of DNP-binding T and B lymphocytes was studied in various states of sensitization and unresponsiveness to DNCB contact sensitivity. In guinea-pigs, where unresponsiveness to DNCB had been established with DNBSO₃ by pretreatment or during the primary response, no increase in antigen-binding cell frequency was found after antigenic stimulation. On the contrary, DNCB-sensitive guinea-pigs, later desensitized with DNBSO₃, showed the same frequency of antigen-binding cells as sensitized animals, although they were unable to react to DNCB.

These results confirm and extend the idea of a different mechanism for `tolerance' and `desensitization' to contact sensitivity.

Differing mechanisms of tolerance and desensitization to dinitrochlorobenzene in guinea pigs

In the present paper the mechanisms of tolerance and desensitization to dinitrochlorobenzene (DNCB) contact sensitivity in guinea pigs were investigated using the methods of adoptive sensitization of tolerant and normal syngeneic recipients and cyclophosphamide-treatment of tolerant animals known to selectively inactivate suppressor lymphocytes. It was shown that desensitization of presensitized animals is caused by the direct effect of the intravenously injected hapten on the effector cells in the peripheral compartment. The immediate onset of unresponsiveness and its very short duration almost exclude the possible involvement of enhancing antibodies or suppressor cells. In the case of tolerance induced by pretreatment with dinitrobenzenesulfonic acid, suppressor cell activity is enhanced, preventing normal specific immunocompetent cells from recognizing the antigen and/or proliferating in the draining lymph nodes. Whether suppressor lymphocytes are of the B or T type is not yet known.

The immunological consequences of antigen overload in experimental mycobacterial infections of mice

Mice infected in the tail with M. ulcerans developed transient cell-mediated immunity which disappeared as the bacterial load increased. Lymph node cells from animals in this late phase of the disease transformed spontaneously in vitro. This transformation was inhibited by mycobacterial antigen. Lymph node cells from mice injected intravenously with 10(8) or 10(9) BCG also transformed spontaneously in vitro. Such animals did not become foot pad test-positive. Evidence is presented that the spontaneous transformation may represent an accumulation of specifically sensitized cells due to trapping in nodes overloaded with persistent antigen. The relevance of such a phenomenon to 'desensitization' in human and animal disease is discussed.

Increased DNA synthesis in vitro in guinea-pigs unresponsive to DNP--skin protein conjugate

Immunological unresponsiveness to DNP—guinea-pig skin protein conjugate (DNP—GPSP) was induced by intravenous injections of dinitrobenzene-sulphonic acid (DNBSO₃) given before, simultaneously, or after sensitization with DNP—GPSP.

The increased DNA synthesis in vitro by lymph node or peritoneal exudate lymphocytes from unresponsive guinea-pigs was suppressed only in animals tolerized by pretreatment with DNBSO₃. The majority of guinea-pigs with the other two types of unresponsiveness showed an increased [³H]thymidine incorporation into lymph node—but not into peritoneal exudate lymphocytes.

From these results two conclusions may be drawn: (1) the mechanism of unresponsiveness induced during the primary response is similar to that of desensitization and different from that of `classical' tolerance; (2) tolerogen given before the sensitization prevents both the increased DNA synthesis by lymph node and peritoneal exudate lymphocytes and the skin reaction. Tolerogen given during the primary response or after the sensitization prevents increased DNA synthesis by peripheral lymphoid cells (peritoneal exudate lymphocytes) and the skin reaction, whereas lymph node lymphocytes showed increased DNA synthesis.

Feedback inhibition of specifically sensitized lymphocytes

An explanation was sought for the fact that delayed-type hypersensitivity (DTH) does not normally occur in response to T-cell-dependent antigens unless an adjuvant is used. But when sheep red blood cells (SRBC) were administered intravenously DTH did appear, provided that the dose of antigen was less than that required to give a maximum antibody response. Animals in which T-cell activity had been blocked by a large dose of antigen could not be sensitized adoptively, and their spleen cells failed to transfer DTH to normal recipients. The serum of blocked animals partially inhibited the induction of DTH, and after absorption with SRBC its blocking activity increased substantially. Moreover, absorbed serum inhibited DTH in previously sensitized animals, but it did not inhibit the proliferative response to SRBC in peripheral lymph nodes or reduce the number of plaque-forming cells produced therein. On the contrary, the hemagglutinating titer was actually increased by blocking serum even though DTH was totally suppressed. It is concluded that a product of the interaction between antigens and antibody blocks the activated T cells which mediate DTH without interfering with helper cells.

Lymphocyte activation. V. Quantitation of the proliferative responses to mitogens using defined T and B cell populations

Although mitogens are frequently used for polyclonal lymphocyte stimulation in both experimental and clinical studies, biological tests of this kind encounter several technical difficulties. The relative importance of some of these were studied by using `calibration curves' for mitogenic stimulation. Thymocytes from cortisone-treated mice (T cells) and spleen cells from T cell-deprived mice (B spleen cells) were mixed in different known proportions and stimulated by Concanavalin A (Con-A), which is a T cell mitogen, or lipopolysaccharide (LPS), which is a mouse B cell mitogen.

We have confirmed earlier observations showing that the amount and specific activity of [³]thymidine have to be adjusted to the culture method used. A linear relationship between the responding cell number and incorporated thymidine was promoted when the extracellular thymidine concentration was constant during the labelling period (16 hr). In our system this could be achieved by adding sufficient amount of thymidine in the form of isotope of relatively low specific activity (50 mCi/mmol). In contrast, when isotope of very high specific activity was used, a low number of responsive cells gave almost `normal' incorporation values.

The validity of the use of mitogens was also tested with the T6 chromosome marker method and cell surface immunoglobulin analysis. It was found that the selective responses of T and B cells to T or B cell specific mitogens were maintained in cultures containing varying numbers of T and B cells. The only indication that B cell activating or `potentiating' factors are released by Con-A-stimulated T lymphocytes was observed in cultures with a high proportion (75%) of `T' cells.

Radio-autographic analysis revealed that under the culture conditions in which the majority of T cells from the spleen were stimulated by Con-A, only 20–30% of B cell population responded to LPS and pokeweed mitogen (PWM).

Migration inhibition of peritoneal exudate cells from sensitized and desensitized rats

The migration of peritoneal exudate cells (PEC) from rats with delayed skin reactivity to diphtheria toxoid (DT) and tuberculin (PPD) was inhibited in the presence of antigen. Three days after an intravenous injection of 2.5 mg of DT there was no inhibition with DT. Seven and 28 days later migration was inhibited but less than in sensitized controls. In 6 weeks the difference disappeared. Three days after the DT challenge, the migration inhibition with PPD was weaker than in the sensitized controls. From day 7 on, non-specific reduction of migration inhibition was not detected. The 24-hour skin reactivity to DT and PPD closely paralleled the in vitro phenomena.

The mechanism of desensitization appears to be the lack or a functional defect of the specific cells or a blocking factor unremovable by washing or produced during the migration assay.

Relationship between tuberculin hypersensitivity and cellular immunity to infection in mice vaccinated with viable attenuated Mycobacterial cells or with Mycobacterial ribonucleic acid preparations

The migration inhibition technique has been used to study delayed hypersensitivity in vitro by using peritoneal exudate cells and splenic lymphocytes from mice vaccinated with viable cells of the attenuated H37Ra strain of Mycobacterium tuberculosis and from mice vaccinated with ribonucleic acid (myc RNA) preparations obtained from viable mycobacterial cells of the same strain. Inhibition of macrophage migration was noted when purified protein derivative (PPD) or viable H37Ra cells were added to peritoneal exudate cells obtained from mice immunized with viable H37Ra cells and not from mice immunized with myc RNA. Splenic lymphocyte cultures were exposed to the same antigens in vitro. Filtered supernatant fluids from these lymphocyte cultures, when added to peritoneal exudate cells obtained from nonimmunized mice, inhibited migration only when they were obtained from lymphocytes which came from mice immunized with viable H37Ra cells. Injection of PPD intravenously into vaccinated mice resulted in inhibitory supernatant fluids from splenic lymphocyte cultures only when the lymphocytes came from mice immunized with viable H37Ra cells. However, intravenous injection of either viable H37Ra cells or of myc RNA preparations into mice vaccinated with myc RNA occasionally produced inhibitory supernatant fluids when lymphocytes were obtained from these mice. On the other hand, mice vaccinated with myc RNA or viable H37Ra cell preparations were consistently and equally protected against intravenous challenge with the virulent H37Rv strain. Thus, although some evidence was obtained for a delayed type hypersensitivity in mice vaccinated with H37Ra cells or with myc RNA to ribosomal proteins or other proteins associated with the RNA preparation, no evidence of tuberculin hypersensitivity could be detected in any mice vaccinated with the myc RNA. These results argue against a role for tuberculin hypersensitivity in immunity to tuberculous infection.

Experimental induction of anergy to coccidioidin by antigens of Coccidioides immitis

Failure to react to coccidioidin (anergy) often occurs in patients with disseminated coccidioidomycosis. One possible reason may be desensitization by excessive amounts of antigen. This was studied experimentally by injection of soluble and hyphal antigens of Coccidioides immitis into coccidioidin- and tuberculin-sensitive guinea pigs. Guinea pigs sensitized by injection of killed hyphal cells of C. immitis in complete Freund adjuvant were subsequently injected daily either with soluble coccidioidal antigen administered intraperitoneally or with hyphal antigen administered either subcutaneously or intraperitoneally. Gradual loss of cutaneous reactivity to coccidioidin occurred, but the reactivity to tuberculin remained unimpaired. The rapidity of desensitization was roughly proportional to the dose of antigen with desensitization occurring as early as 6 days after beginning injections. This anergic state was temporary, and reactivity returned several days after discontinuing injection of antigen. Injection of coccidioidal antigen led to production of coccidioidal complement-fixing antibody, but there was no consistent relationship between the antibody titer and state of cutaneous reactivity to coccidioidin. Peritoneal exudate or pulmonary alveolar cells from desensitized animals migrated freely in the presence of coccidioidin but were inhibited in the presence of tuberculin. Heat treatment did not impair the capacity of the soluble or hyphal antigen to induce anergy, thus suggesting that the antigen active in complement fixation was perhaps not involved in desensitization. Polysaccharide obtained by ethanol precipitation of dialyzed coccidioidin failed to induce anergy. Dialysis of the soluble coccidioidal antigen caused the loss of the desensitizing activity. Thus, specific desensitization could be induced by administration of large doses of coccidioidal antigen but dialyzable components appear important in this desensitization.

Specificity of a BCG-induced pulmonary granulomatous response in rabbits

The specificity of Bacillus Calmette Guérin (BCG)-induced accelerated pulmonary granuloma formation has been evaluated in rabbits by cross sensitization-challenge experiments by using another granulomagenic organism, Corynebacterium granulosum. BCG-sensitized rabbits responded to challenge with homologous but not heterologous antigen, indicating that BCG-induced accelerated granuloma formation displays specificity characteristic of immunological reactions. These differences were also observed in local pulmonary delayed hypersensitivity, as determined by the migration inhibition test. The relationship between local pulmonary delayed hypersensitivity and the accelerated granulomatous response is discussed.

Relationship of BCG-induced pulmonary delayed hypersensitivity to accelerated granuloma formation in rabbit lungs: effect of cortisone acetate

The role of local pulmonary delayed hypersensitivity in accelerated pulmonary granuloma formation was investigated using cortisone acetate, an immunosuppressive drug that appears to preferentially eliminate committed lymphocytes at appropriate doses. Data are presented showing that cortisone acetate suppressed local pulmonary delayed hypersensitivity at the time of and subsequent to challenge with BCG. Furthermore, cortisone damage appeared to involve primarily committed lymphocyte populations since the defect was repairable with sensitized spleen cells, an unlikely source of macrophage precursors.