Primary cell-mediated immune response in bronchial asthma. Relationship between primary in vitro and in vivo cell-mediated and antibody responses in patients with asthma and healthy controls

Eleven patients with asthma and ten sex and age matched healthy controls were immunized with the primary immunogen Helix pomatia Haemocyanin (HPH). The amplitude and the kinetics of in vitro cell-mediated immune response were measured by HPH-induced lymphocyte proliferation. Lymphocytes were also challenged in vitro with mitogens and recall antigens. In vivo cell-mediated immunity was determined by inducing delayed type hypersensitivity reactions with HPH. Anti-HPH antibody responses in the IgE, IgG and IgM classes were measured to gain an insight into the relation between cell-mediated and humoral immune responses in patients with asthma and healthy controls. The in vitro and in vivo cell-mediated response and the IgM antibody response did not differ between patients with asthma and controls. The IgE and IgG antibody responses, however, were increased in the patients. IgM antibody response correlated with both the in vitro and in vivo cell-mediated response (R= 0.45, P<0.05). IgE and IgG antibody responses however were not correlated with cell-mediated responses. These data suggest that the primary abnormality in immune regulation in patients with asthma concerns the control of the IgE and IgG class antibody responses.     

The effect of cyclosporine on immunization with tetanus and keyhole limpet hemocyanin (KLH) in humans

Eleven patients with chronic uveitis treated with Cyclosporine were immunized with keyhole limpet hemocyanin (KLH) and tetanus toxoid. Delayed cutaneous hypersensitivity responses, lymphocyte blastogenic responses, and antibody production were compared with those of similarly immunized control individuals. A significant decrease in delayed cutaneous hypersensitivity (P<0.001 for KLH andP<0.01 for tetanus toxoid) was observed. No significant differences in blastogenic or antibody responses were noted. These findings demonstrate that the majority of the Cyclosporine-treated patients had intact T cell-dependent antigen responses as measured by both proliferative response and antibody production to primary and secondary antigenic challenges but that other immune functions such as delayed cutaneous hypersensitivity are affected by therapeutic doses of systemic Cyclosporine.     

Impaired T8 lymphocyte-mediated suppressive activity in patients with partial Di George syndrome

We have studied thein vitro B-cell maturation induced by pokeweed mitogen of lymphocytes from seventeen patients with partial Di George syndrome. These patients were characterized by a low number of T8(+) lymphocytes. They had normal immune functions with an increased level of serum IgE for most of them. These patients were investigated before the age of 1 month. In contrast to age-matched subjects, their lymphocytes were able to producein vitro immunoglobulins, although the level of immunoglobulin production was lower than in adults. These data were explained by a lack of T-cell mediated suppressor activity normally found in newborns. There was a strong correlation between the low number of T8(+) lymphocytes and the magnitude of thein vitro immunoglobulin production by patients' cells. This was further demonstrated by the ability of residual T8(+) lymphocytes isolated from patients to normally suppress the PWM driven B cell maturation on a per cell basis. The defective T-cell mediated suppression progressively disappears within 5 months. It is possible that this phenomenon is secondary to a delayed differentiation of suppressor T-cells in patients with partial Di George syndrome.     

Intrinsic and extrinsic asthma, a shared lymphocyte abnormality

We have examined in vitro cell-mediated lymphocyte responses to Concanavalin A, (Con. A), and the effects of histamine and indomethacin upon these responses, in normal subjects, and patients with extrinsic and intrinsic asthma, and chronic bronchitis. Lymphocytes from both intrinsic and extrinsic asthmatics are particularly sensitive to histamine-induced suppression of their response to Con. A, and this increased sensitivity was reversed by indomethacin. In these respects, lymphocytes from intrinsic and extrinsic asthmatics behave in an identical fashion, but differ significantly from lymphocytes from both normal subjects and patients with fixed airways obstruction (chronic bronchitis). It is suggested that there is a common immunological mechanism in extrinsic asthma and intrinsic asthma.     

Methionine-enkephalin as immunomodulator therapy in human immunodeficiency virus infections: Clinical and immunological effects

Enkephalins have been shown to enhance T cell-mediated immune responses and natural killer-cell activityin vitro. We have studied the effects of infusions of methionine-enkephalin on immune functions and clinical courses in seven patients with various stages of infection with human immunodeficiency virus (HIV). All patients were clinically stable at the time of entry into the study. Each received 10 µg/kg of methionine-enkephalin in an intravenous infusion three times weekly for up to 12 weeks. Evaluation of cellular immunity (T-cell subsets,in vitro interleukin-2 production and interleukin-2 receptor expression, T-cell responses to mitogens and antigens, and delayed-hypersensitivity skin tests) as well as clinical and toxicity monitoring was performed prior to treatment, at 2-week intervals during treatment, and after the cessation of treatment. Increases in interleukin-2 receptor expression were seen on lymphocytes collected on one occasion from each of two patients 30 min postinfusion. Studies done 24 hr after infusions revealed increases in interleukin-2 production in one patient, but when pre- and posttreatment values were compared there were no significant changes in numbers of circulating T cells of any phenotype or in T-cell responses to mitogens or antigens. None of the patients with Kaposi's sarcoma had regression of tumor; one patient dropped out of the study at week 5 because of deteriorating clinical status and progression of tumor. There were no adverse reactions or evidence of toxicity. We conclude that methionine-enkephalin appears to enhance temporarily selected immune responses in patients with HIV infection, however, in the schedule used in this study it was not clinically efficacious.     

Mast cells and basophils in cutaneous immune responses

Mast cells and basophils share some functions in common and are generally associated with T helper 2 (Th2) immune responses, but taking basophils as surrogate cells for mast cell research or vice versa for several decades is problematic. Thus far, their in vitro functions have been well studied, but their in vivo functions remained poorly understood. New research tools for their functional analysis in vivo have revealed previously unrecognized roles for mast cells and basophils in several skin disorders. Newly developed mast cell‐deficient mice provided evidence that mast cells initiate contact hypersensitivity via activating dendritic cells. In addition, studies using basophil‐deficient mice have revealed that basophils were responsible for cutaneous Th2 skewing to haptens and peptide antigens but not to protein antigens. Moreover, human basophils infiltrate different skin lesions and have been implicated in the pathogenesis of skin diseases ranging from atopic dermatitis to autoimmune diseases. In this review, we will discuss the recent advances related to mast cells and basophils in human and murine cutaneous immune responses.     

Variable cell-mediated immune defects in a family with `Candida endocrinopathy syndrome'

The in vivo and in vitro cell-mediated immune (CMI) responses of a family of nine members, three of which are affected with `Candida endocrinopathy syndrome' (CES), have been investigated. No abnormal CMI responses were detected in any of the non-affected members.

The three patients were found to have low numbers of T-cell rosettes. Patient number 1 demonstrated inconsistent in vitro lymphocyte response to Candida extract (CE), with absent migration inhibition factor (MIF) release despite the positive skin reactivity to CE. The patient's serum was found to block the CE-induced response of control lymphocytes. Patient number 2 showed absent delayed cutaneous reactivity to CE associated with absent in vitro lymphocyte response, as well as absence of MIF release in response to this antigen. His serum contained inhibitory activity for the Candida-induced response of control lymphocytes. Patient number 3 demonstrated similar defects to patient number 1, but the serum blocking factor was not found.

Our finding that all affected individuals demonstrated a variety of defects in their CMI responses to CE suggests variable phenotypic expressivity in the presence of the gene responsible for the inheritance of CES. Administration of transfer factor in two of the affected individuals resulted in an increase of T-cell rosettes in both patients, conversion of skin reactivity to CE in one of them, and augmentation of skin reactivity to this antigen followed by partial clinical improvement in the other.

     

Juvenile rheumatoid arthritis: cellular hypersensitivity and selective IgA deficiency

Although humoral immune mechanisms are currently thought to be of pathogenetic significance in juvenile rheumatoid arthritis (JRA), little is known about the role of cellular hypersensitivity in this disease. A possible association between abnormalities of humoral and cellular immunity exists in patients with ataxia-telangiectasia, who may have absent IgA, abnormal delayed hypersensitivity, or both. As IgA deficiency has been noted in 2–3% of patients with JRA, we have studied selected aspects of humoral and cellular hypersensitivity in patients with JRA and IgA deficiency and in patients with JRA and normal IgA levels. All patients had normal serum levels of complement, IgG, IgM, and IgD.

Cellular hypersensitivity was evaluated by cutaneous delayed-type hypersensitivity, in vitro migration inhibitory factor production, and antigen induced 3H-thymidine incorporation by lymphocytes using Candida and Streptokinase–Streptodornase antigens. Two of four IgA deficient patients had positive in vitro but negative in vivo responses to antigens. Seven of fourteen JRA patients with normal immunoglobulin levels exhibited a similar dissociation of in vivo and in vitro manifestations of delayed hypersensitivity. This pattern of cellular immune response was associated with activity and chronicity of disease; it was independent of IgA deficiency.

     

Inhibitory effects of low molecular weight heparin on mediator release by mast cells: preferential inhibition of cytokine production and mast cell-dependent cutaneous inflammation

There has been substantial evidence that suggests that heparin may modulate various aspects of immune function and inflammation in addition to its well known anticoagulant activity. In this regard heparin was found to suppress cell-mediated immune responses or asthmatic reactions to allergen challenge. In the present study we analyse the effects of low molecular weight heparin (LMWH) on mast cell degranulation and cytokine production in vitro and on the elicitation of IgE-mediated mast cell-dependent late cutaneous allergic inflammation in vivo. We have established that LMWH preferentially inhibited tumour necrosis factor-alpha (TNF-α) and IL-4 production without having any significant effect on mast cell degranulation. These effects have been observed in mast cells derived from three different origins that were activated by either immunological or non-immunological stimuli. We have shown that there is inhibition of TNF-α production (and not neutralization of activity), as elimination of the drug after a short preincubation and addition of LMWH to rTNF-α had no effect on TNF-α-mediated cytotoxic activity. These results were also confirmed by ELISA. In vivo, s.c. injection of the LMWH inhibited the leucocyte infiltration associated with the late cutaneous response which followed passive cutaneous anaphylaxis (PCA) reaction, without affecting mast cell numbers or degranulation. These data suggest that LMWH may have an inhibitory role in mast cell-mediated allergic inflammation, and thus might be considered as a possible therapeutic modality.     

Altered immunity in hemophilia correlates with the presence of antibody to human T-cell lymphotropic virus type III (HTLV-III)

Twenty-nine heterosexual patients with hemophilia were investigated with histories, physical examinations, laboratory evaluations of immune function, delayed hypersensitivity skin tests, and assays for antibody to human T-cell lymphotropic virus type III (HTLV-III). Sixteen patients were HTLV-III antibody positive and 13 were HTLV-III antibody negative. No patient had the acquired immune deficiency syndrome (AIDS). Patients who had antibody to HTLV-III had received significantly more units and lots of factor concentrates in the preceding 5 years than those who did not have antibody. HTLV-III antibody-positive patients had significantly fewer total T cells (Leu-1 positive) and significantly fewer helper T cells (Leu-3 positive) than HTLV-III negative patients. Antibody-positive patients also had increased amounts of IgG and decreased thymidine incorporation in response to concanavalin Ain vitro. There were no differences inin vitro lymphocyte responses to phytohemagglutinin (PHA), pokeweed mitogen,Candida, tetanus, or purified protein derivative (PPD), no significant impairments of gamma interferon or interleukin-2 (IL-2) production, and no anergy. Ten patients with antibody to HTLV-III had immunologic studies repeated 1 year after the original evaluation. A significant increase was seen in suppressor (Leu-2-positive) T cells but not in total T-cell or helper T-cell numbers, helper/suppressor ratios, or T-cell functional assays. We conclude that the immune abnormalities in hemophiliacs are the result of contact with HTLV-III but that these abnormalities may remain stable over prolonged periods.     

Immunization with extracellular proteins of Mycobacterium tuberculosis induces cell-mediated immune responses and substantial protective immunity in a guinea pig model of pulmonary tuberculosis.

We have studied the capacity of a selected fraction of Mycobacterium tuberculosis extracellular proteins (EP) released into broth culture by mid-logarithmic-growth-phase organisms to induce cell-mediated immune responses and protective immunity in a guinea pig model of pulmonary tuberculosis. Guinea pigs infected with M. tuberculosis by aerosol but not uninfected control guinea pigs exhibit strong cell-mediated immune responses to EP, manifest by dose-dependent cutaneous delayed-type hypersensitivity and splenic lymphocyte proliferation. Guinea pigs immunized subcutaneously with EP but not sham-immunized control guinea pigs also develop strong cell-mediated immune responses to EP, manifest by dose-dependent cutaneous delayed-type hypersensitivity and splenic lymphocyte proliferation. EP is nonlethal and nontoxic to guinea pigs upon subcutaneous immunization. Guinea pigs immunized with EP and then challenged with aerosolized M. tuberculosis exhibit protective immunity. In five independent experiments, EP-immunized guinea pigs were consistently protected against clinical illness, including weight loss. Compared with EP-immunized guinea pigs, sham-immunized control guinea pigs lost 12.9 +/- 2.0% (mean +/- SE) of their total weight. EP-immunized guinea pigs also had a 10-fold reduction in viable M. tuberculosis bacilli in their lungs and spleens (P = 0.004 and 0.001, respectively) compared with sham-immunized control animals. In the two experiments in which some guinea pigs died after aerosol challenge, EP-immunized animals were protected from death. Whereas all 12 (100%) EP-immunized guinea pigs survived challenge with aerosolized M. tuberculosis, only 6 of 12 (50%) sham-immunized control guinea pigs survived challenge (P = 0.007, Fisher exact test). This study demonstrates that actively growing M. tuberculosis cells release immunoprotective molecules extracellularly, that a subunit vaccine against tuberculosis is feasible, and that extracellular molecules of M. tuberculosis are potential candidates for a subunit vaccine.     

Phosphatidylinositol Mannosides are Efficient Mucosal Adjuvants

The development of defined sub-unit vaccines requires the inclusion in the vaccine of an immunological adjuvant. The most important property of adjuvants for vaccines aimed at inducing optimal protection against intracellular bacteria such as Mycobacterium tuberculosis or M. bovis is the ability to enhance cell-mediated immunity, specifically Th1 responses. In this paper, we describe a system where transgenic mice expressing a high proportion of T cells specific for an ovalbumin (OVA) peptide are used to assess the ability of a novel class of adjuvants to positively modulate cell-mediated immune responses. Defined fractions containing purified native or synthetic phosphatidylinositol mannosides (PIMs) from mycobacteria were assessed for their adjuvant activities in response to the model antigen (OVA). Purified PIM preparations given to mice with OVA by the subcutaneous route were shown to elicit an enhanced release of interferon-gamma (IFN-γ) in cellular responses to OVA peptide in vitro. Very little interleukin-4 (IL-4) was released by cells from mice immunized with PIMs and OVA, whereas cells from animals immunized with complete Freund's adjuvant (CFA) and OVA released IL-4 as well as IFN-γ. Synthetic preparations of PIM2 and PIM4 also acted as adjuvants in the mouse model studied. In addition, PIM preparations were shown to generate an efficient cell-mediated immune response to OVA, when the antigen/adjuvant preparations were administered via the oral route or intranasal route. PIM preparations elicited substantial release of interleukin-12 (IL-12) from dendritic cells (DCs). These data suggest that purified or synthetic PIMs act as adjuvants when administered at mucosal surfaces and represent a new class of adjuvants for mucosal immunization against intracellular pathogens.     

The human primary immune response to keyhole limpet haemocyanin: interrelationships of delayed hypersensitivity, antibody response and in vitro blast transformation

The immune response to a protein antigen, keyhole limpet haemocyanin, was studied in fourteen normal subjects and twenty-one patients with solid tumours. Immunological responsiveness was assessed by intracutaneous skin testing, by haemagglutinin titres and by in vitro blast transformation. No significant difference was found in the kinetics or magnitude of the immune response among subjects immunized with 0·01, 0·10, or 5·0 mg. Delayed hypersensitivity to keyhole limpet haemocyanin developed in thirty-two of thirty-four skin tested; a positive antibody titre occurred in all; and thirty-one of thirty-five had positive in vitro responses. Patients in good general condition (Group 1) had significantly greater delayed hypersensitivity and antibody responses than the normals but similar in vitro responses. All immunological parameters were depressed in the patients with advanced neoplastic disease (Group 2).

Although only skin test positive subjects had positive in vitro responses, no direct correlation was found between the degree of delayed hypersensitivity and the degree of in vitro blast transformation. Excellent correlation was demonstrated, however, between the in vitro response and the haemagglutinin titre (correlation coefficient +0·52, standard error ±0·09).

     

Increased T cells lacking immunoglobulin Fc receptors and increased spontaneous morphological blast transformation in a patient with phycomycosis

A 64-year-old diabetic man had phycomycotic infection withRhizopus and expired following surgical debridement. Extensive immunological evaluation revealed normal cellular and humoral immune responses including anin vivo response toRhizopus antigen following delayed hypersensitivity skin testing. Evidence for increasedin vivo lymphocyte activation consisted of increased spontaneous morphological blast transformation and increased T non-mu non-gamma cells. This work extends the previous findings of normal immunological responsiveness includingin vitro reactivity toRhizopus antigen in such patients.     

Chronic mucocutaneous moniliasis with impaired delayed hypersensitivity

Three patients, including two brothers, with chronic mucocutaneous moniliasis and endocrinopathy were evaluated from an immunological viewpoint. Each patient had defective delayed hypersensitivity to Candida albicans as manifested by a negative skin test and absent lymphocyte response after in vitro exposure to the antigen. Cutaneous responses to other antigens were intact, and there were no demonstrable abnormalities in humoral immunity. In one case, the in vitro lymphocyte response was restored following an injection of a leucocyte extract from a skin test positive subject, although the cutaneous lesions remained unchanged.

It is possible that cells of both the endocrine and lymphoid systems share a defect in synthesis and release of their respective humoral products. In the case of lymphoid cells, the defect would be limited to populations of cells participating in delayed hypersensitivity, and impair production of mediators such as macrophage migration inhibiting factor, lymphotoxin, etc., while sparing the processes of antibody synthesis. Alternatively, the selective failure in delayed hypersensitivity may result from defective lymphocyte differentiation or from loss of immune responsiveness through densensitization by chronic exposure to the fungal antigens.

     

Immunological monitoring in patients with end-stage renal disease

Parameters of cell-mediated immune function were determined in 76 patients with end-stage renal disease. Lymphocyte subpopulations (OKT3, OKT4, OKT8, OKIal, OKM1, OKT9, OKT10), natural killer (NK)-cell activity (percentage⁵¹Cr release from K562 targets), and delayed cutaneous hypersensitivity were measured and correlated with other variables. The results indicate that (1) uremic patients have a significant diminution in the OKT4-lymphocyte subpopulation and OKT4/OKT8 (helper/suppressor) ratio compared to normal controls; (2 blood transfusions do not induce significant alterations in the helper/suppressor-cell ratio; (3) uremic patients have a significant increase in OKM1 cells compared to normal controls; (4) the majority of uremic patients in this series developed delayed cutaneous hypersensitivity responses to recall antigens and could be de novo sensitized to 2,4-dinitrochlorobenzene (DNCB); (5) skin-test reactivity could not be correlated with total circulating T cells or levels of any lymphocyte subpopulations; and (6) NK-cell activity in uremic patients is not significantly different from that in normal controls. These results highlight the varying levels and function of different lymphocyte subsets in patients with end-stage renal disease when they are treated with chronic maintenance hemodialysis.     

Lymphoproliferative and Gamma Interferon Responses to Stress-Regulated Mycobacterium avium subsp. paratuberculosis Recombinant Proteins

Johne''s disease in ruminants is a chronic infection of the intestines caused by Mycobacterium avium subsp. paratuberculosis. An important strategy to control disease is early detection, and a potentially efficient method for early detection is measurement of cell-mediated immune responses developed by the host in response to exposure or infection. One method is to measure lymphoproliferation and cytokine release from the host cells when exposed to the organism or parts of the organism. In this study, 10 recombinant M. avium subsp. paratuberculosis proteins known to be upregulated under in vitro stress conditions were evaluated by examining their ability to evoke memory as a result of exposure by vaccination or oral challenge with live Mycobacterium avium subsp. paratuberculosis. Out of 10 proteins, MAP2698c was found to induce higher cell-mediated immune responses in vaccinated and challenged sheep in comparison to healthy controls. The findings suggest that not all stress-regulated proteins have the diagnostic potential to detect cell-mediated immune responses in ovine paratuberculosis.     

A synthetic analogue of phosphatidylinositol mannoside is an efficient adjuvant

We recently described the synthesis of an ether linked analogue of phosphatidylinositol dimannoside (PIM₂ME). In the current study, PIM₂ME was found to significantly enhance the release of the key Th1 cytokine interleukin-12 (IL-12) by dendritic cells (DCs) of naïve mice in vitro, but not interleukin-10 (IL-10). Based on this result, it was hypothesized that PIM₂ME would be an effective adjuvant for cell-mediated immune responses. Injections of PIM₂ME alone did not lead to weight loss and did not have toxic side effects, based on biomarkers of toxicity in serum,demonstrating that the compound induced no apparent adverse side effects. Mice were vaccinated with the core antigens of the hepatitis C virus by itself or with three different adjuvants, namely PIM₂ME, a commercial preparation of monophosphoryl lipid A (MPL) or a preparation of aluminium hydroxide gel (alum). A control group of animals received the antigen only with no adjuvants. Immune responses to the Hepatitis C viral antigens were monitored by measuring antigen-specific production of interferon-gamma (IFN-γ), the p40 subunit of interleukin-12 (IL-12) and interleukin-10 (IL-10) to assess cell-mediated immune responses. Vaccination of mice with Hepatitis C viral antigens with the adjuvant PIM₂ME led to a significant increase in cell-mediated immune responses (IFN-γ and IL-12). Injection of Hepatitis C viral antigens in alum led to no enhancement of the cell-mediated immune response. We conclude that PIM₂ME is an efficacious adjuvant for enhancing cell-mediated immunity, and induces no observable adverse effects.     

Immune complexes are potent inhibitors of interleukin-12 secretion by human monocytes

We have studied the effect of immune complexes (IC) on interleukin (IL)-12 secretion by human monocytes in vitro. Two experimental models of IC were used. IC formed of tetanus toxoid and polyclonal anti-tetanus toxoid antiserum as well as heat-aggregated human serum IgG almost completely inhibited IL-12 (p70 and p40) secretion induced by interferon-γ and lipopolysaccharide in human blood-derived monocytes. Neutralizing anti-IL-10 antibodies plus indomethacin restored IL-12 secretion in the presence of IC to a high extent, indicating that IL-10 and prostaglandin (PG) partially mediate the IC-induced inhibition of IL-12 secretion. However, neutralization of tumor necrosis factor (TNF)-α by specific antibodies also incompletely restored IL-12 secretion. Indeed, monocytes secrete high levels of TNF-α upon stimulation by IC. We found that exogenously added TNF-α caused a profound inhibition of monocytic IL-12 secretion in the absence of IC, again mediated via the induction of IL-10 and PG. In summary, IC inhibit IL-12 secretion via TNF-α-induced IL-10 and PG synthesis. We conclude that IC, typically appearing in the course of chronic inflammatory processes, may influence the balance between Th1 and Th2 responses and may thus contribute to a deprivation of cell-mediated immune responses.     

Experimental cutaneous leishmaniasis. II. Effects of immunosuppression and antigenic competition on the course of infection with leishmania enriettii in the guinea-pig

Intradermal inoculation of the guinea-pig with Leishmania enriettii results in a self-healing cutaneous lesion which provides a laboratory model of human cutaneous leishmaniasis and which is dominated by cell-mediated immunological responses (Bryceson et al., 1970). In this study we sought to design experimental situations resembling non-healing forms of cutaneous leishmaniasis in man and to determine whether these experimental situations were accompanied by abnormalities in the immunological response to infection. This paper describes three procedures which impair the resistance of guinea-pigs to leishmanial infection: (i) induction of partial immunological tolerance to leishmanial antigen; (ii) systemic injection of anti-lymphocyte serum (ALS); and (iii) regional antigenic competition produced by multiple injections of bacterial adjuvants.

Injection of soluble leishmanial antigen (PSA) during the third week of foetal life suppressed resistance to neonatal infection with L. enriettii; local infections were severe and were accompanied by metastatic spread and by impaired development of delayed hypersensitivity (DH). Injection of PSA into the 6-week foetus and into the adult guinea-pig led to impaired DH after leishmanial infection, but resistance to infection was only slightly suppressed. Transient impairment of DH was induced by a short injection course of adult animals with ALS during the first 3 weeks of infection, which resulted in large primary lesions with temporary metastatic spread.

Multiple regional injections of tubercle- and corynebacterial-adjuvant emulsions markedly suppressed resistance to subsequent leishmanial infection; large ulcerative lesions were accompanied by widespread nodular metastases, the unusual appearance of haemagglutinating antibody, and death of some animals.

There was no impairment of DH to PSA; in fact, this was temporarily enhanced during the first 6 weeks of leishmanial infection of the tubercle-adjuvant group. This suppression of resistance could not be attributed to systemic desensitization of DH to bacterial antigen or to the local sclerosing effects of adjuvant emulsion; the term `regional antigenic competition' was therefore employed. Both the induction of partial tolerance and the injection of ALS selectively impaired paracortical responses in lymph nodes draining leishmanial infections; however, in regional antigenic competition the lymph nodes were infiltrated with macrophages but both follicular and paracortical responses were prominent.

Suppression of resistance to L. enriettii was not related simply to impairment of DH; for there was overall dissociation of protective, allergic and antibody responses in these suppressed animals. The relationship of cellular immune mechanisms to cutaneous leishmaniasis was viewed in two ways. First, it was inferred that resistance of guinea-pigs to L. enriettii requires both successful induction of cell-mediated immunity and functional integrity of the regional lymphoid system at the time of infection. Second, it was suggested that nonhealing forms of human cutaneous leishmaniasis may arise from defective coordination of surveillance, inflammatory and adjuvant functions of the cellular immune response to leishmanial antigens. It was concluded that interference with cellular immune responses in the guinea-pig led to experimental infections which resembled some features of more generalized cutaneous leishmaniasis in man.