Suppression of delayed hypersensitivity in vitro by inhibition of protein synthesis

In vitro interactions of immune lymphocytes and Cryptococcus neoformans

CBA/J mice immunized subcutaneously with emulsions of heat-killed Cryptococcus neoformans in complete Freund adjuvant displayed delayed-type hypersensitivity to cryptococcal culture filtrate antigen and developed sensitized splenic lymphoid cells which inhibited the growth of C. neoformans in vitro. The in vitro assay of growth inhibition served to investigate further the kinetics of the effect of sensitized lymphoid cells on the pathogen. There was a close correlation between the delayed-type hypersensitivity response in mice and inhibition of growth of C. neoformans by lymphoid cells. Sensitized splenic lymphocytes capable of inhibiting the growth of the cryptococci were detected at day 6 after immunization and reached maximum levels by days 8 through 16. Inhibition of growth was highest with effector-to-target cell ratios of 300:1 or greater. Inhibition of growth of C. neoformans by sensitized lymphoid cells was detectable as early as 4 h after effector and target cells were mixed and increased gradually, reaching a maximum at 24 h, but dropped significantly by 48 h. By supplementing the reaction mixtures with fresh medium or additional sensitized effector cells during incubation, the inhibition of growth of C. neoformans could be maintained through 48 h. C. neoformans-sensitized effector lymphoid populations not only inhibited the growth of the pathogen in vitro but also restricted C. neoformans proliferation in various vital organs upon transfer to naive recipient animals, indicating that the in vitro growth inhibition assay may be a means of assessing the resistance of animals to C. neoformans. The effector cells from sensitized animals were nylon wool-nonadherent Thy-1+ and Ia+ lymphocytes.

Cell-mediated immunity to gluten within the small intestinal mucosa in coeliac disease

Jejunal biopsies from controls and coeliac patients were maintained in organ culture in the presence of gluten fraction III. The culture media were assayed for evidence of lymphokine activity in a migration inhibition test using normal peripheral blood leucocytes. Significant inhibition of migration was produced by media from untreated coeliac patients compared with controls (P less than 0.005) or treated coeliac patients (P less than 0.001), indicating the production of a leucocyte migration inhibition factor (LIF) by untreated coeliac mucosa in response to gluten fraction III. The degree of inhibition correlated with the preculture interepithelial lymphocyte count in the coeliac biopsies (P less than 0.02). In six coeliac patients studied when on a normal diet and on a gluten-free diet, LIF was produced while on a normal diet, but not while on a gluten-free diet. These results suggest that a local cell-mediated immune reaction to gluten is present in the mucosa of patients with untreated coeliac disease but that this is reversed by treatment with a gluten-free diet.

Inhibition of mitogen-induced lymphokine production by cyclosporin A

The new antilymphocytic agent Cyclosporin A was found to inhibit the production and/or secretion of migration inhibitory factor (MIF) in human lymphocytes stimulated by Concanavalin A. Preincubation for one hour with the compound, followed by 8 hr restoration period of the cells in absence of the drug, resulted in moderate decrease in MIF synthesis and/or release. Cell viability was not affected. The agent was shown not to interfere with MIF action on the macrophage. We conclude that the molecular mechanism of action of Cyclosporin A is based, at least partially, on a blockade of synthesis and/or secretion of lymphokines from immunocompetent cells.

The effect of cortisone acetate on pulmonary lesions in a rabbit model of hypersensitivity pneumonitis (cortisone and hypersensitivity pneumonitis)

Rabbits were sensitized with Micropolyspora faeni by intratracheal inoculations and later challenged with the same antigen either with or without parenteral administration of cortisone acetate prior to challenge. Animals developed anti-M. faeni serum precipitins, M. faeni-induced alveolar macrophage migration inhibition, and positive 48-hr skin reactivity to M. faeni. Sensitized animals also demonstrated an augmented pulmonary histopathological response following respiratory challenge with M. faeni when compared to non-sensitized controls. Cortisone acetate abrogated this augmented pulmonary histopathological response following challenge with M. faeni. Cortisone acetate also abolished the positive alveolar macrophage migration inhibition found in sensitized animals.

Mechanisms responsible for antibody-dependent, cell-mediated cytotoxicity to isolated hepatocytes in chronic active hepatitis

Lymphocytes from patients with chronic active hepatitis have been found to be cytotoxic for isolated rabbit hepatocytes. Although this reaction has been shown to be of the antibody-dependent type, no autologous serum was added to the assay system and in the present experiments the source of the antibody has been sought. The failure of puromycin to block the reaction argued against a role for antibody synthesised during the culture period, and the demonstration that normal mononuclear cells could become cytotoxic when preincubated in chronic active hepatitis sera was more in favour of the passive acquisition of an antibody from the circulation. Evidence for the existence of free antibody in the sera reacting with hepatocyte surface antigens came from an additional series of experiments in which it was shown that preincubation of hepatocytes in chronic active hepatitis sera rendered them susceptible to damage by normal mononuclear cells. This effect was almost completely abolished by adding a membrane lipoportein fraction of human liver (LSP) to the sera during the preincubation step, suggesting that the LSP contained those antigens on the hepatocyte surface against which the majority of the antibodies were directed.

Biological and clinical relevance of human macrophage migration inhibitory factor (MIF)

The first isolation and characterization of a lymphokine, the human MIF (MSF), and the availability of a specific MIF (MSF)-antibody provide an opportunity to establish a new parameter for detection of cellular immune mechanisms in various clinical situations. The precise estimation of quantitative amounts of MIF by sensitive immunochemical techniques could gain new insights into the pathogenesis of a number of clinical disorders. In addition, the exact detection of quantitative amounts of MIF in body fluids could have prognostic value.

Use of a radioactive double labeling technique in the chemical analysis of the mediators of cellular immunity

Radioactive double labeling was adapted for the analysis of mediators of cellular immunity. Two identical lymphocyte cultures were simultaneously labeled with [3H]- or [14C]leucine. Each of the cultures was stimulated with antigen or mitogen. The combined supernatants were then subjected to various fractionation procedures. By determining the isotope ratio in each fraction it is possible to identify those products of activated lymphocytes that have been produced either de novo or in increased amounts. The method proved sensitive enough to detect lymphocyte activation products in supernatants of activated lymphocyte cultures from guinea pig, mouse, and man.

Effect of immunosuppressive drugs on an in vito correlate of cell-mediated immunity. The migration inhibition test

The effect of a number of immunosuppressive drugs on the migration-inhibition test was studied. These drugs could be divided into four categories: (1) drugs influencing both the MIF production and MIF effect on macrophages (amethopterin, azathioprine); (2) drugs influencing MIF production (puromycin, actinomycin D); (3) drugs influencing the effect of MIF on macrophages (hydrocortisone); (4) drugs without any influence.

Measles virus-induced migration inhibition of human leukocytes in vitro: an expression of cell-mediated immunity?

Attempts were made to establish measles virus-induced migration inhibition of human leukocytes as an in vitro test of cell-mediated immunity to the virus. Crude material from cell cultures infected with two different strains of measles virus was used as antigen in the capillary modification of the test. Both virus preparations induced migration inhibition. Incubation with puromycin indicated that the inhibition was dependent on protein synthesis, which has been regarded as a characteristic feature of an immunologically specific inhibition. However, no difference was found when the migration inhibition of leukocytes from donors without clinical and serological evidence of previous measles infection was compared with that of leukocytes from donors with such evidence. It is concluded that the migration inhibition induced by crude measles virus material does not necessarily measure cell-mediated immunity to the virus.

Interdigitating reticulum cells in the popliteal lymph node of the rat. An ultrastructural and cytochemical study

Electronmicroscopic and cytochemical studies were performed to localize interdigitating reticulum cells (IDC) in the popliteal lymph node of the rat. The morphological features of the IDC of the rat correspond to those described for other species, but also show similarities to normal macrophages in the rat. This is considered to be an argument in favour of the common origin of IDC's and macrophages. Ultrahistochemical studies with horseradish peroxidase (HRP) reveal no phagocytotic capacity of IDC's. After perfusion fixation containing ruthenium red (RR) the surface coat stains heavily: RR is also found deep in the membrane invaginations of the IDC, indicating the presence of polyanionic sialoglycoproteins. The post-capillary-venules (PVC) are very permeable to both HRP and RR. The phosphotungstic acid-chromic acid stain (PTA-CrA) also reveals glycoproteins in the surface coat; these glycoproteins are susceptible to alpha-neuraminidase, whereas glycoproteins in the Golgi complexes, lysosomes and in the vesicular complexes of IDC are not. The glycoproteins of the latter are susceptible to 0.1 N NaOH. These findings indicate that IDC produce different kinds of glycoprotein, one of which may be secreted and act as a factor for stimulating peripheral T-lymphocytes. Intimate contact between IDC's and PCV's could be observed. It is therefore conceivable that IDC's play an important role in the homing of T-lymphocytes.

In vitro activity of guinea pig transfer factor released into plasma

Plasma fractions and plasma dialysate from 2,4-dinitrochlorobenzene- and tuberculin-sensitive guinea pigs that had been treated with either antilymphocytic serum or normal control serum were analyzed for their ability to transfer lymphocyte transformation, passive cutaneous anaphylaxis, and macrophage migration inhibition, as well as delayed hypersensitivity in vivo. Antilymphocytic serum caused rapid release of material, which has characteristics of transfer factor, into the plasma. It was dialyzable, migrated electrophoretically with the alpha globulins and albumin, possessed a 280/260 (nm) optical density ratio of 0.7, and caused in vitro lymphocyte transformation in the presence of the specific antigen. Passive cutaneous anaphylaxis antibodies were also present in the plasma of sensitive animals, but they were isolated in electrophoretic or dialysis fractions separate from those containing transfer activity.

Two stages in lymphocyte mediator production by differential susceptibility to blockade using niridazole

Sera from guinea pigs given niridazole, an anti-schistosomal compound, have been shown to reversibly block the production of antigen-induced migration inhibitory factor by sensitized guinea pig lymph node cells. Since niridazole itself has no effect in vitro, the blockade of production of migration inhibitory factor is probably due to drug metabolites in the serum. We report here further studies on the mechanism of this drug-induced suppression of cellular hypersensitivity; the data show that niridazole active serum does not block the production of migration inhibitory factor once it has been initiated. Indeed, if niridazole active serum is added a little as 60 sec after the addition of antigen, the lymphocytes will produce migration inhibitory factor. These results suggest the presence of at least two stages in production of migration inhibitory factor after the addition of antigen to lymphocytes. The first, lasting less than 60 sec, is susceptible to blockade by niridazole active serum; the second is not. The elucidation of the mechanism of this blockade should lead to further understanding of the early events after antigen triggering of sensitized lymphocytes.

An animal model of hypersensitivity pneumonitis in the rabbit

This study was devised to produce an animal model of hypersensitivity pneumonitis in order to study both the induction and the elicitation of the disease. Rabbits exposed by aerosol to large quantities of pigeon antigens developed a humoral, but not cellular, immunologic response. Moreover, their lungs were essentially normal histologically. A single i.v. injection of killed BCG in oil permitted the induction of pulmonary cell-medid hypersensitivity to the inhaled antigen, as well as the development of pulmonary lesions which were more severe than that caused by the administration of BCG alone. The humoral immunologic response to the inhaled antigen was not increased after BCG injection. Since many individuals are exposed to the etiologic agents of hypersensitivity pneumonitis for extended periods without developing the disease, these findings in animals suggest that some event may occur to induce cell mediated hypersensitivity in order to initiate the disease process. In addition, we have shown that animals with normal lung histology and circulating complement-fixing antibodies undergo serum complement (CH50) depression after an aerosol challenge with the specific antigen. Animals with circulating, complement-fixing antibodies, and inflamed lungs (BCG-induced failed to undergo a complement depression subsequent to an aerosol challenge with specific antigens. These results re consistent with those seen in symptomatic and asymptomatic pigeon breeders and suggest that antigen distribution through the lung is important in the pathogenesis of hypersensitivity pneumonitis.

Effect of freezing and storing on the biological properties of macrophages

Storage of intact macrophages would be a useful procedure for laboratories studying the biological functions of these cells. Oil-induced guinea pig peritoneal cells were harvested and frozen at an ultra-low temperature using a cryoprotective media. Studies of the biological properties of the frozen cells upon thawing indicated that the cells retained viability for a fairly long period of time, were metabolically active and comparable to normal cells in morphology. Indications of activation were obtained in enhanced phagocytic activity and significant decrease in migration of the stored cells.

An in vitro assay of leukocyte migration inhibitory activity from human lymphocytes stimulated with concanavalin A

Human venous blood lymphocytes, incubated for 22 h in serum-free culture medium with the plant mitogen concanavalin A (Con-A), elaborated products, which inhibited the migration of human buffy coat cells under agarose. Con-A was removed by applying the supernatants on small Sephadex G-100 columns. The leukocyte migration inhibitory activity (LMIA) was tested in a semi-quantitative modification of the indirect leukocyte migration agarose technique, which is described. Lymphokine activity, demonstrable as early as 9 h after activation of lymphocytes, was most pronounced after 22 h. Significant LMIA was demonstrated in 12 of 17 normal individuals at standard dilution of culture supernatants I/3. In 9 of the 12 experiments, assays of LMIA were carried out on stepwise diluted supernatants with detection of the greatest dilution with significant LMIA. In four experiments LMIA could only be detected after 3- to 12-fold concentrations of supernatants. Considerable individual variation was found, the amounts of LMIA varying by a factor of about 300. The reproducibility appeared to be quite high, but the factor stability of supernatants stored at -20 degrees C was surprisingly low.

On the relation of products of activated lymphocytes to cell-mediated cytolysis

Experiments have been designed to test the hypothesis that soluble mediator production and T-cell-mediated cytotoxicity are necessarily related phenomena, and that soluble mediators may be involved in the mechanism of cytolysis. To this end, agents known to inhibit T-cell-mediated lysis in vitro have been studied for their effects on the production of two lymphocyte-derived mediators, lymphotoxin (LT) and migration inhibitory factor (MIF). A clear dissociation between mediator production and cell-mediated cytolysis was found using inhibitors of protein synthesis. Pactamycin and emetine, in doses of 10(-7) M to 10(-6) M, suppressed production of MIF and LT with only slight effect on killing of mastocytoma cells by immune T cells. On the other hand colchicine and vinblastine inhibited T-cell-mediated cytolysis in a dose-related manner but had no significant effect on either MIF or LT production, A striking dichotomy was also observed after augmentation of intracellular cyclic 3'5' adenosine monophosphate (cAMP) levels with cholera enterotoxin. Increased cAMP levels were associated with abrogation of direct lytic activity, but were without significant effect on MIF or LT production in guinea pigs or mice. These findings indicate that mediator production and direct lymphocyte-mediated cytolysis can be experimentally dissociated and represent independent cell-mediated immune functions.

The significance of circulating and cell-bound antibodies in experimental allergic encephalomyelitis

Conjugates of horseradish peroxidase with myelin basic protein (BP) of guinea pig or Lewis rat were used to identify antibody-containing cells in draining lymph nodes during experimental allergic encephalomyelitis (EAE). Peroxidase activity was revealed for light and electron microscopic preparations with the diaminobenzidine reaction of Graham and Karnovsky. Basic proteins (BP) were also iodinated with (125)I for determination of circulating antibody against BP by radio-immunoassay of (125)I BP using coprecipitation with antirat IgG or with antirat serum proteins. Encephalitogenicity was lost after conjugation of guinea pig BP or Lewis rat BP with peroxidase, whereas iodination did not affect the encephalitogenicity of guinea pig or Lewis rat BPs. EAE was induced in Lewis rats with guinea pig or Lewis rat spinal cord BPs in complete Freund's adjuvant. Draining lymph nodes were studied by light and electron microscopy during the course of the immune reaction, and cells with specific antibody against BP were identified with the use of BP-horseradish peroxidase conjugates. Lymph node sections from animals immunized with high antigen doses (500 mug) showed numerous plasma cells with intracellular antibody against BP in medullary cords 10 days after immunization and 4 days prior to histologic appearance of EAE. Numbers of positive cells correlated with levels of circulating antibody against BP. Immunization with a low antigen dose (5 mug) resulted in EAE, few or no antibody-containing cells, and significantly lower levels of circulating antibody. Brown Norwegian rats, a strain resistant to EAE, immunized with 500 mug of BP had positive cells in draining lymph nodes and high levels of circulating antibody against BP in the absence of histologic evidence of EAE. Lewis rats injected with Lewis rat small BP failed to develop EAE. Nevertheless, these animals showed levels of circulating antibody and antibody-containing cells similar to those of animals which developed EAE after injection of the mixture of Lewis rat large and small BP. It is concluded that although the BP-peroxidase labeling method reveals cells with specific anti-BP antibody, these cells are probably unrelated to EAE. The lack of correlation between EAE induced by low antigen doses and levels of circulating anti-BP antibody (determined with the use of highly encephalitogenic (125)I-BP) suggests that effector cells can be stimulated at low antigen doses, but higher antigen doses are required to induce the production of levels of circulating antibody detectable by the method of immune coprecipitation.

The immunology of experimental Chagas' disease. 3. Rejection of allogeneic heart cells in vitro

Experiments that consisted of incubation of Trypanosoma cruzi-sensitized lymphocytes derived from chronically infected rabbits and from rabbits repeatedly immunized with a small particle or membrane fraction derived from homogenates of T. cruzi forms, showed destruction of allogeneic, parasitized and nonparasitized heart cells in vitro. Mononuclear cells collected from peripheral blood were incubated for 1 h at 37 degrees C to isolate the lymphocytes. Following incubation, over 99% of the cells in the supernate were lymphocytes, which were utilized in these experiments. At the start of these experiments, 70-80% of the sensitized lymphocytes were unattached, small and round, with sparse filipodia. In the ensuing hours, marked heart cell destruction, similar to that seen in an active lesion when lymphocytes invade heart tissue, were observed. After 18 h incubation, about 65-70% of the lymphocytes were attached, larger, and rough surfaced. Inhibition of monocyte migration tests, each in the presence of the antigens of subcellular fractions of T. cruzi organisms and of allogeneic heart myofibers, indicated the presence of a cross-reacting antigen common to both the parasite and the heart in the small particle or membrane fractions. The particulate antigens of the 30,000 g, 35-min fraction of heart muscle gave rise to inhibition of monocyte migration as did the counterpart fraction derived from T. cruzi organisms. The destruction of nonparasitized target heart cells by T. cruzi-sensitized lymphocytes is an in vitro model of the chronic myocarditis of Chagas' disease, and the recognition of cross-reactive antigens of the host cell by T. cruzi-sensitized lymphocytes is believed to be the pathogenic basis for subsequent tissue injury in the chronic phase of this disease.

Respiratory tract cell-mediated immunity: comparison of primary and secondary response

A secondary local and splenic cell-mediated immune response was observed and compared to the primary response. Previous studies have demonstrated cell-mediated immunity (CMI) by lymphocytes from bronchopulmonary washings and have shown that its appearance is to a large extent inedpendent of splenic CMI. This study evaluated the secondary as compared to the primary response, with respect to both cellular and humoral immune responses. Guinea pigs were immunized with influenza virus vaccine either nasally or parenterally, booster immunizations were given by the same route, and animals were killed at various times after immunization or booster. The inhibition of macrophage migration was used to assess CMI. As in previous studies, local application of antigen led to mainly local appearance of CMI, whereas parenteral immunization led to mainly systemic CMI. Both pulmonary and splenic lymphocytes showed an inhibition of macrophage migration that appeared 2 to 3 days sooner after the booster, as compared to the primary immunization. There was no evidence, however, for the earlier production or increased amount of antibody in the bronchial secretions in the boosted animals. The results suggest that pulmonary as well as splenic T lymphocytes exhibit memory, but that pulmonary B lymphocytes do not.

Amplification of migratory inhibition factor production during the first 48 hours of exposure to antigen

When lymphocyte-macrophage suspensions from sensitized animals are preincubated with specific antigen for 24 or more h, the following results are observed. (i) In a standard capillary macrophage migration test, there is complete inhibition of migration. (ii) When the preincubated cell suspension is mixed in varying proportions with a similar suspension from nonsensitized animals and a macrophage migration test is performed, there is no linear relationship between the degree of inhibition of migration and the proportion of sensitized lymphocytes initially present. Inhibition thus appears to be an "all-or-none" effect. (iii) In spite of the second observation, increasing periods of preincubation with antigen result in increasing inhibition. (iv) These results suggest the existence of a complex amplifying mechanism operating within the early period of exposure to antigen. (v) To test the possibility that cell proliferation contributes to this amplification, cells from sensitized guinea pigs were irradiated with a dose of 1,000 rads prior to preincubation with antigen. Despite this dose, which virtually abolishes cell division in other systems, no diminution whatever in the amplification of inhibition was observed. These results suggest the existence of an early phase of increased production of migratory inhibition factor that is not dependent on cell division but that may be related to "recruitment" of nonsensitized lymphocytes.

Alveolar macrophage migration inhibition in animals immunized with thermophilic actinomycete antigen

Intratracheal immunization of rabbits with Micropolyspora faeni, a thermophilic actinomycete known to be a rich source of `farmer's lung hay' antigen leads to development of pulmonary lesions similar to those noted in human hypersensitivity pneumonitis and in antigen induced MIF production by sensitized respiratory tract lymphocytes.

MIF release was not specific for the respiratory route of immunization since immunization via the toe pad route using Freund's adjuvant also resulted in antigen induced migration inhibition of alveolar wash cells.

If macrophage migration inhibition can be regarded as an in vitro correlate of cell mediated (type IV) hypersensitivity, our results suggest that this type of hypersensitivity plays a role in pathogenesis of experimentally induced hypersensitivity pneumonitis.

In vitro studies of the cell-bound and antibody-mediated immunity evoked by murine renal allotransplants. Influence of presensitization, total body irradiation and immunosuppressive agents

The influence of presensitization, total body irradiation and several immunosuppressive drugs on the immune response evoked by allogeneic rat kidneys was studied in vitro and in vivo. The cytotoxic effect of recipient thoracic duct lymphoid cells and fresh or heat-inactivated recipient serum against donor target cells was measured with ⁵¹Cr assay.

Rats that had undergone two consecutive allogeneic transplantations from isogenous donors had thoracic duct lymphoid cells and serum with an increased cytotoxic effect against donor strain target cells as compared to control rats transplanted only once. Heat-inactivated recipient serum from such animals also had an increased blocking effect on cell-mediated cytotoxicity.

ALS had the strongest depressive effect on the cell-bound immunological responses evoked by the transplants in the recipient rats, decreasing both the number of lymphoid cells in the thoracic duct lymph and the cytotoxic activity of the remaining cells. Methylprednisolone and methotrexate also strongly suppressed the cellular immunological events in the way just mentioned. Actinomycin-C and total body irradiation depressed cell-bound immune response only by causing a decrease in the number of cells in the thoracic duct lymph. Azathioprine did not influence cell-bound immunological responses to allogeneic kidney transplants.

Total body irradiation, methotrexate and methylprednisolone treatment markedly diminished the cytotoxic effect of fresh recipient serum against target cells and reduced the blocking effect of heat-inactivated recipient serum on lymphoid cell-mediated cytotoxicity. The other tested agents all caused a moderate depression of the cytotoxic and blocking effect of fresh and heat-inactivated recipient serum, respectively.

When folinic acid was given regularly between consecutive methotrexate injections, the depression of the lymphoid cell amount in the thoracic duct lymph was markedly less. The results of the cytotoxicity tests were similar to those obtained with methotrexate treatment alone.

Products of activated lymphocytes. I. The use of radiolabeling techniques in the characterization and partial purification of the migration inhibition factor of the guinea pig

General methods were developed and applied to the biosynthesis and purification of products of activated lymphocytes available in minute quantities. The activity studied here was the migration inhibitory factor (MIF) produced by purified protein derivative (PPD)- or concanavalin A (Con A)-stimulated lymphocytes obtained from one guinea pig or less. The methods selected yielded results in terms of two chemical parameters characteristic of the molecules involved, namely K(d) on Sephadex G-75 and isoionic point, pI, on isoelectric focusing. When supernatants were fractionated on G-75 columns, there were several areas even in control supernatants which produced migration inhibition relative to medium controls. However, in PPD- and Con A-stimulated supernatants, at least one peak of MIF activity was found solely in the stimulated cultures, with a K(d) of 0.15. A double-labeling technique was used to characterize the proteins of this peak. Control, unstimulated cultures were labeled with [(14)C]leucine and stimulated cultures were labeled with [(3)H]leucine. After mixing the supernatants and G-75 filtration, a major "ratiolabeled" broad peak. i.e. one with increased (3)H/(14)C ratio, was found. When a narrow portion of this peak about K(d) 0.15, containing most of the MIF activity, was subjected to analytical isoelectric focusing, all of the label was associated with proteins of lower net charge than albumin. A unique ratiolabeled peak was found in PPD- and Con A-stimulated fractions with a pI of approx. 5.3. A micropreparative isoelectric focusing technique was developed and yielded MIF activity in the same region as the major ratiolabeled peak. Further study will be required to ascertain whether the ratiolabeled protein is MIF. By following the K(d), pI, and (3)H/(14)C labeling ratio, at least 14 products of activated lymphocytes, synthesized either de novo or in increased amounts, could be distinguished.

Evaluation of the leucocyte migration test as a measure of delayed hypersensitivty in man. Suppression of migration inhibition by puromycin

The response of peripheral blood leucocytes to PPD was studied in vitro by means of the leucocyte migration test, using Mantoux-positive and -negative subjects. The migration of leucocytes from 83% of the positive subjects was significantly inhibited when a concentration of 100 μg PPD/ml was used in the chambers. Leucocytes from the majority of these subjects were also inhibited at a lower concentration of 50 μg PPD/ml and one strongly positive subject showed inhibition at all concentrations tested, down to 1 μg PPD/ml. Stimulation of migration was not observed with leucocytes from any of the positive subjects even when the lowest concentration of PPD was used. Inhibition of migration with PPD was prevented by the addition of puromycin, suggesting that the response is dependent on protein synthesis and may be mediated by a soluble factor produced by sensitized lymphocytes.

Production of macrophage migration inhibition factor by continuous cell lines

Macrophage migration inhibitory factor (MIF) was found in media of human and mouse lymphocyte and fibroblast cell lines that were continuously growing. Its release was dependent on activation of the cells to enter the mitotic cycle, particularly on cells in S phase. The greatest quantity of MIF was detected in supernatants of lymphocytes collected during S phase after the cells were synchronized in G(1) and in supernatants of growing fibroblasts. When the latter were contact inhibited little or no MIF was found in media. MIF was also released into media of cells proliferating in homologous serum in the absence of fetal calf serum and into media lacking any protein. The MIF produced by lymphocyte lines eluted from Sephadex G-100 in the same fashion as MIF produced by the interaction of sensitized guinea pig cells and antigen. The results indicated that MIF is not a specific mediator of delayed hypersensitivity and cellular immunity and that MIF released by sensitized lymphocytes incubated with antigen merely reflects that fraction of cells activated by antigen to enter the mitotic cycle.