Regulation of delayed hypersensitivity. Failure to transfer delayed hypersensitivity to desensitized guinea pigs

Reactivity to trichophytin antigen in patients with onychomycosis: effect of terbinafine

BACKGROUND

Many patients with chronic dermatophytosis and onychomycosis have depressed cell-mediated immunity (CMI) to trichophytin.

OBJECTIVE

The fungicidal properties of oral terbinafine provide a unique opportunity to explore whether elimination of antigen could restore CMI response in these patients.

METHODS

A double-blind, placebo-controlled study evaluated the effect of terbinafine (250 mg/d for 12 weeks) on skin immunoreactivity to intradermal trichophytin antigen (TRIPA), mycologic status of the nail, and nail growth in patients with toenail onychomycosis.

RESULTS

Skin reactivity, in an optimized, dose response challenge series to TRIPA was inversely related to disease chronicity. Mycologic/clinical response rates were 72%/84% for terbinafine and 0%/7% for placebo. Terbinafine increased the number of TRIPA reactors 2-fold and the mean TRIPA reaction area 4-fold; responses in placebo-treated patients were relatively unchanged. Of the 7 (of 25) patients receiving terbinafine who still had positive mycology 6 months after treatment, all were anergic to TRIPA at baseline and all but one remained so after treatment.

CONCLUSION

Terbinafine treatment enhances and restores CMI to TRIPA in patients with Trichophyton rubrum onychomycosis and may thereby reduce susceptibility to reinfection. Terbinafine reversal of immunologic anergy may be an important model of microbial tolerance in chronic dermatophyte infections.

Immunology of sarcoidosis

Because of its association with cutaneous anergy, sarcoidosis was originally viewed as a defect of cellular immunity. Supporting that misperception were early studies of peripheral blood lymphocytes that found lymphopenia and impaired lymphocyte responses to mitogens and recall antigens. The clue to a vast underlying network of complex hyperactive cellular immune functions was discovered in the paradoxical finding of in vitro spontaneous lymphoblastic transformation and lymphokine production. Subsequently, investigative focus shifted to the activated, proliferating T-helper lymphocytes, the lymphokines of which were found to function in the recruitment and retention of monocytes for granuloma development. T-helper lymphocytes also contributed to the mechanism of hypergammaglobulinemia through their influence on B cells. The most intriguing question about sarcoid immunology is the initiating factor that triggers the T-lymphocyte activation and proliferation in the first place. There is much to suggest that antigen processing and presentation launches the process. Because lymphocyte activation and proliferation antedate granuloma formation at K-S skin test sites and in the lung, we combined the harvesting technique of BAL with the K-S bioassay to show that granulomagenic antigen is being processed by monocyte-macrophages. The finding of autologous monocyte-macrophage granulomagenicity raises the distinct possibility that sarcoidosis is a unique cell-mediated type of autoimmune process. The isolation and identification of the granulomagenic factor is the exciting research frontier ahead.

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.

Antigen-specific inhibition of IL-2 and IL-3 production in contact sensitivity to TNP

The production of IL-2 and IL-3 by T cells from mice which had been contact sensitized to TNP and/or tolerized by intravenous injections of TNBS was assayed. Contact sensitization rapidly primes T cells, so that they respond to in vitro restimulation with haptenated syngeneic cells by producing IL-2 and IL-3. This production is strongly inhibited, in an antigen-specific manner, in tolerized mice. At least part of this inhibition can be attributed to the action of suppressor T cells that act by preventing the activation of lymphokine production in vitro. Lymphokine production thus closely parallels the in vivo delayed-type hypersensitivity (DTH) reaction in this system.

Role of cytokines in the restoration of the delayed-type hypersensitivity reaction of anergic patients

Soluble mediators from peripheral blood lymphocytes activated either by skin test antigens or by alloantigens restored the delayed type hypersensitivity (DTH) reaction in the majority of anergic surgical patients who are at increased risk for sepsis and mortality. Antigen had to be injected together with the mediators and the individual had to be reactive to the antigen for restoration. These results suggest that restoration of the DTH response depends on the ability of cytokines produced and acting in a non-specific manner to promote the response of the anergic patients' specific antigen-sensitive cells to antigen.

Cell-mediated immunity in experimental murine dermatophytosis. II. Adoptive transfer of immunity to dermatophyte infection by lymphoid cells from donors with acute or chronic infections

An in vivo adoptive cell transfer system was used to investigate protective immunity during experimental murine dermatophytosis due to Trichophyton quinckeanum. Using sublethally (550R) irradiated BALB/c mice which are particularly susceptible to infection, it was found that regional lymph node cells from syngeneic acutely-infected donors conferred protection to irradiated recipients. By contrast, serum from the same donors did not prevent infection of normal BALB/c mice. The capacity of lymphoid cells to transfer adoptive immunity was lost after treatment with monoclonal anti-Thy-1.2 antibody and complement, but not after treatment with monoclonal anti-Ly 2.2 antibody and complement, indicating that cellular immunity is mediated by Ly 2-T cells. The cellular activity of chronically infected mice was also studied. Paradoxically, lymphoid cells from these animals which appeared to be immunologically compromised did, however, confer immunity. Adoptive immunity was abrogated by serum from chronically infected donors or by specific dermatophyte antigen, but not by homologous or heterologous anti-dermatophyte antiserum. These findings indicate that competition between cell-mediated immunity and humoral factors may be the causative mechanism for persistence of dermatophyte infection in this system.

Effect of cyclophosphamide on immunological control mechanisms

Cyclophosphamide (CY) given before immunization causes greatly increased delayed hypersensitivity skin reactions. Increased cell-mediated immunity is associated with depletion of B-lymphocytes from lymphoid tissue and a depression of those lymphocytes whose precursors turn over more rapidly. In the guinea pig, replacement studies showed that the depleted cells were not T-lymphocytes and had immunoglobulin adherent to their surface, a characteristic of B-lymphocytes. Delayed hypersensitivity reactions increased by CY include chemical contact sensitivity, the tuberculin reaction, delayed hypersensitivity to tularemia vaccine and the Jones-Mote reaction to soluble protein antigens. Pretreatment with CY can also increase the antibody response to some antigens, but depress the response to others. In addition, CY has been found to reverse immunological tolerance where this form of unresponsiveness is due to suppressor cells. CY can also enhance the immune response following depression by antigenic competition or desensitization. Other drugs with a similar, but lesser, effect include melphalan, azathioprine and methotrexate.

Diseases associated with immunosuppression

Impairment of any of the major components of the immune system (T-cells, B-cells phagocytes, complement) may result in clinical immunodeficiency. Immune defects can arise from intrinsic or heritable defects of lymphoid elements, failure of normal cellular differentiation, viral infection or other acquired causes. Clinical impairment of immunity is expressed as a marked susceptibility to opportunistic and pathogenic organisms which are difficult to control and by an increased risk of malignancy, allergy and autoimmune disease. Certain immunodeficiency disorders are associated with aberrant immune regulation. The major types of immune deficiency are characterized by unique patterns of infections depending on the level at which the defect occurs and the pathogenic mechanisms of the parasite. The basic defects of representative primary and secondary immunodeficiencies are discussed in relation to observed immunologic consequences.

The effect of cyclophosphamide and role suppressor cells in the desensitization of delayed hypersensitivity

Desensitization of guinea-pigs with ovalbumin (OA) or bovine gamma globulin (BGG) induces strong specific desensitization and is associated with a non-specific energy to tuberculin--PPD. Similarly, it was found that animals receiving desensitizing injections of PPD have suppressed delayed hypersensitivity reactions to OA or BGG. PPD also induced strong specific desensitization. Cyclophosphamide (CY) given in one large dose (300 mg/kg) 3 days before immunization failed to affect the specific desensitization induced by all three antigens. However, if CY was given 1 day after immunization, it was not possible to induce specific desensitization. The induction of non-specific desensitization was prevented in all three antigen systems if CY was given either 3 days before or 1 day after immunization. Desensitization with either OA or BGG markedly suppressed the specific 4 hr Arthus reactions.

Suppressor T-cells in BCG-infected mice

Specific pathogen-free B6D2 hybrid mice were infected with high (10(8) cells, intravenous), moderate (10(6) cells, intravenous), and low 10(3) cells, aerogenic) doses of viable BCG Pasteur. The growth of the BCG in the lungs and spleens of the three groups was followed over a 90-day period and correlated with the level of tuberculin hypersensitivity. Spleen cells were harvested from the three groups of mice at increasing time intervals and filtered through nylon wool to remove adherent cells, and the level of blast transformation after exposure to phytohemagglutinin and purified protein derivative was determined. Early in the BCG infection both the high- and the intermediate-dose groups showed enhanced thymidine incorporation by the spleen cell cultures, followed by a profound depression late in the infection. At this time, both groups of mice were anergic to purified protein derivative injected into footpads. Cell mixing studies demonstrated the presence of a population of suppressor cells in the spleens of the anergic animals. The suppressive abilities of these cells would be ablated by treatment with anti-Thy-1 antiserum and complement. The aerogenically infected mice were unresponsive to purified protein derivative but showed no evidence of suppressor T-cells. The lack of tuberculin sensitivity in these mice seemed to be due to a lack of sensitized T-cells in the spleen rather than to active immunosuppression.

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.

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.

In vivo suppression of delayed hypersensitivity: prolongation of desensitization in guinea pigs

Administering moderate (milligram) amounts of antigen to a guinea pig immunized with thatntigen leads to a transient loss of all delayed hypersensitivity (DH) responses in that animal. In this study, we demonstrate that this "desentization" can be prolonged for 10 days by repeated injection of antigen. At this time, tolerance to the desensitizing antigen develops in both the humoral and cellular systems of the immune response and DH responsiveness to other antigens returns. Repeated cycles of sensitization and desensitization produce repeated episodes of generalized anergy. Neither cells nor serum from desensitized animals could be shown to exert a suppressor effect when transferred to immunized animals and the cells responded normally to antigen and mitogen in tissue culture. The best generalized depression of DH was seen in those animals producing the best DH before desensitization. The inability of antigen to react with tolerant cells to produce desensitization suggests that this phenomenon is an active rather than a passive one and may represent an exaggeration of a normal regulatory mechanism for DH triggered by a regimen of antigen administration that activates suppressor cells to produce a systemic effect.

The multiple mixed lymphocyte reaction: variables important in the test as a measure of lymphocyte competence in man

In order to utilize the mixed lymphocyte reaction (MLR) as an assay of T-lymphocyte competence, pools of target lymphocytes obtained from different individuals are used to increase the magnitude and decrease the variation of the in vitro response. We evaluated variations in MLR response due to variations in target cell populations. Response increased with an increased target/responder cell ratio. Peak response occurred with a target/responder cell ratio of between 1:1 and 1:4. Response to a pool of lymphocytes from different individuals increased as the number of individuals contributing to the pool increased. Peak stimulation occurred with three to four different donors to the target cell pool. Stimulation produced by pooled target cells resulted in a higher mean index of stimulation and decreased variation of response as compared to stimulation produced by target cells from individual donors. Stimulation produced by pooled target cells was approximately equal to the sum of the stimulation produced by each of the target cell populations acting alone. These findings indicate a practical method of modifying the MLR as a test of T-lymphocyte function.

Suppression of tuberculin skin reactivity by prior tuberculin skin testing

In two consecutive studies, eighteen and forty-one normal subjects were given a standard tuberculin skin test of 1 tuberculin unit (0.02 mug of PPD). Two days later another skin test was given. Readings of the skin reactions showed that subjects exhibiting strongly positive skin reactions in their primary skin tests showed a significantly smaller indurations in their primary skin tests tended to have equal or larger areas of induration after the secondary skin tests. These observations are discussed in relation to the possible existence of regulatory mechanisms of cell-mediated immune reactions.

The effect of plasma upon lymphocyte response in vitro. Demonstration of a humoral inhibitor in patients with sarcoidosis

The role of humoral inhibitors of lymphocyte functions was evaluated in subjects with sarcoidosis. A reproducible system was developed to evaluate the capacity of human plasma samples to support lymphocyte responses in vitro to PHA and to Candida albicans antigen.

There was an unacceptable ten-fold variation in lymphocyte response to PHA among cultures that contained different individual samples of normal plasma. However, when any three normal plasma samples were pooled, the variation was reduced to two-fold. Seven out of twenty-five individual normal plasma samples tested did not support stimulation as well as a pool of plasma.

In contrast, autologous plasma sustained normal lymphocyte stimulation as well as or better than pooled homologous plasma. We tested the ability of plasma from subjects with sarcoidosis to support the stimulation of autologous lymphocytes by PHA and antigen, and compared this response to that obtained when the same lymphocytes were stimulated in cultures that contained pooled normal plasma. Lymphocytes of thirteen out of twenty-six subjects with sarcoidosis did not respond to in vitro stimulation in their own plasma as well as they did when cultured in the pooled plasma of normal subjects. Plasma of fourteen out of twenty-five patients with sarcoidosis caused a significant decrease in the response of normal lymphocytes to PHA, even when added to optimal concentration of pooled normal plasma. We conclude that the plasma of patients with sarcoidosis contains an inhibitor of lymphocyte stimulation.

Temporary suppression of lymphocyte transformation after tuberculin skin testing

Sixteen normal subjects were studied to see if a tuberculin skin test (Mantoux) would induce changes in their cell-mediated immune response (CMIR) as determined by a lymphocyte transformation test (LTT). In ten Mantoux-positive persons, a significant suppression of the responses to stimulation with both purified protein derivative (PPD) and phytohaemagglutinin (PHA) occurred. The suppression was seen within a week of the skin test. In three Mantoux-negative persons, an increase was seen in the response to stimulation with PPD, together with a significant suppression of the response to stimulation with PHA. Antibodies to PPD were found in low titres, but the titres did not change during the period of suppression of CMIR. The results show that a transient suppression of CMIR can be induced in normal individuals by the application of a small dose of antigen.

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.

Dose response relationships and interference of simultaneous skin tests in delayed hypersensitivity

The relationship between the intensity of the delayed hypersensitivity reaction and the dose of antigen used for its elicitation change with time after sensitization. At three weeks the reactions to 100 mug of egg albumen were little different from those to 1 mug but at 14 weeks 100 mug gave much stronger reactions. This means that to follow the development of a delayed hypersensitivity response several antigen doses should be used. If two skin tests were performed simultaneously in the same individual, the stronger one suppressed the weaker one, regardless of whether two different doses of the same antigen or two different antigens were used. Consequently, not more than one skin test at a time should be performed.