Effects of rosiglitazone (PPAR γ agonist) on the myocardium in non-hypertensive diabetic rats (PPAR γ)

BACKGROUND

There is ongoing controversy regarding the safety of rosiglitazone and its effects on the myocardium, in some cases causing severe cardiac pathology and even in some instances mortality. In this study we aimed at examining the effects of pharmacologic doses of rosiglitazone on cardiomyocytes in diabetic non-cardiac rats receiving sub-optimal doses of insulin.

METHODS

Animals were distributed into six groups: normal, diabetic, and diabetic receiving insulin, each subdivided into a control group and an experimental group receiving pharmacologic doses of rosiglitazone. Cardiomyocyte hypertrophy was assessed using heart to body weight index and microscopic examination using the number of cardiomyocytes per quadrant of high power field and intercalated disks in a sector of 100 × field. Fibrosis was assessed using Masson Trichrome staining. A number of sections of each group were stained with periodic acid Shiff and others with Sudan III for glycogen and fat accumulation, respectively. One way ANOVA was used for statistical analysis as appropriate.

RESULTS

Diffuse cardiomyopathic changes in diabetic control animals were observed consisting of cardiomyocyte hypertrophy, loss of striations and widespread vacuolation. These changes were reduced and even prevented by treatment with insulin and rosiglitazone. Masson staining showed that all rat groups had no more than +1 fibrosis that is equal to what was present in the normal controls.

CONCLUSION

Rosiglitazone, in combination with even sub-optimal doses of insulin therapy, has protective effects on cardiac muscle in diabetic animals especially those expressed as muscle hypertrophy, muscle cell death, and fibrosis.

Role of glucagon-like peptide-1 and its agonists on early prevention of cardiac remodeling in type 1 diabetic rat hearts

Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted from intestinal L cells upon nutrients ingestion, and is currently used for treating diabetes mellitus. It plays an important role in receptor modulation and cross talk with insulin at the coronary endothelium (CE) and cardiomyocytes (CM) in diabetic type 1 rat heart model. We studied the effects of insulin, GLP-1 analogues (exendin-4), and dipeptidyl peptidase-IV (DPP-IV) inhibitor on GLP-1 cardiac receptor modulation. The binding affinity of GLP-1 to its receptor on CE and CM was calculated using a rat heart perfusion model with [(125)I]-GLP-1(7-36). Tissue samples from the heart were used for immunostaining and Western blot analyses. GLP-1 systemic blood levels were measured using ELISA. GLP-1 binding affinity (τ) increased on the CE (0.33 ± 0.01 vs. 0.25 ± 0.01 min; p < 0.001) and decreased on the CM (0.29 ± 0.02 vs. 0.43 ± 0.02 min; p < 0.001) in the diabetic non-treated rats when compared to normal. There was normalization of τ back to baseline on the CE and CM levels with insulin and DPP-IV inhibitor treatment, respectively. Histological sections and immunofluorescence showed receptor up-regulation in diabetic rats with significant decrease and even normalization with the different treatment strategies. Systemic GLP-1 levels increased after 14 days of diabetes induction (10 ± 3.7 vs. 103 ± 58 pM; p = 0.0005). In conclusion, there is a significant GLP-1 receptor affinity modulation on the CE and CM levels in rats with diabetes type 1, and a cross talk with GLP-1 analogues in early prevention of cardiac remodeling.

Effect of Systemic Insulin and Angiotensin II Receptor Subtype-1 Antagonist on Endothelin-1 Receptor Subtype(s) Regulation and Binding in Diabetic Rat Heart

This study reports on the regulation and remodeling role of endothelin-1 (ET-1) and its receptor subtypes, ET(A)-Rs/ET(B)-Rs, at the coronary endothelium (CE) and cardiomyocyte (CM) sites. It is carried out in normal and normotensive rats with streptozotocin-induced diabetes mellitus receiving different treatment modalities. Normal rats were divided into two groups, namely a placebo (N) and a losartan-treated (NL), and diabetic rats into four groups receiving placebo (D), insulin-treated (DI), losartan-treated (DL), and insulin/losartan-treated (DIL) respectively. Binding kinetics of ET-1 to ET(A)-Rs/ET(B)-Rs on CE and CMs were assessed in the above groups to try to explain the effect of therapeutic doses of an angiotensin II receptor subtype-1 blocker on the dynamics of this ligand and its receptor in insulin supplemented diabetic animals. Each group was divided into two subgroups: CHAPS-untreated and CHAPS-treated rat hearts perfused with [125I]ET-1 to respectively estimate ET-1 binding affinity (tau = 1/k-n) to its receptor subtype(s) on CE and CMs using mathematical modeling describing a 1:1 reversible binding stoichiometry. Heart perfusion results revealed that insulin treatment significantly decreased tau on CE but not on CMs in diabetic rats. In diabetics treated with losartan, an increase in tau value on CE but not on CMs was noted. Cotreatment of diabetic rats with insulin and losartan normalized tau on CE but decreased it on CMs. Western blot, using snap-frozen heart tissues, revealed increase in ET(A)-R density in all diabetic groups. However, significant decrease in ET(B)-R density was observed in all groups compared to the normal, and was reconfirmed by immunohistochemical analysis. In conclusion, coadministration of insulin and losartan in nonhypertensive animals suffering from diabetes type 1 may offer new cardiac protection benefits by improving coronary blood flow and cardiomyocyte contractility through modulating ET-1 receptor subtypes density and affinity at CE and CM sites.

Leishmaniasis of the auricle mimicking carcinoma

Leishmaniasis of the auricle has been rarely reported in our region of the world, where it is labeled as "Old World Leishmaniasis." It may mimic other pathologies, such as malignancies or other infectious processes. We present a case of an auricular Leishmania lesion which was first suspected to be a carcinoma. Four previous auricular Old World Leishmania cases have been reported. The epidemiology, clinical presentation, diagnosis, and treatment of this entity are briefly reviewed.

Effect of type-1 diabetes mellitus on the regulation of insulin and endothelin-1 receptors in rat hearts

This project assesses the treatment role with insulin and (or) angiotensin II receptor subtype-1 (AT1-R) blocker (ARB) on insulin receptor and endothelin-1 receptor subtype (ETA-R and ETB-R) regulation in rat hearts suffering from insulin-dependent diabetes mellitus (IDDM). Animals were divided into 6 groups: groups 1, 3, and 5 were controls consisting of normal, diabetic (streptozotocin-treated, once at 0 time), and diabetic supplemented daily with insulin, respectively, whereas groups 2, 4, and 6 were the controls treated daily with losartan. One month after enrollment, rats were sacrificed and samples of cardiac tissue were snapped frozen for immunostaining and Western blotting. Insulin receptor density was observed to be upregulated in the cardiomyocytes of diabetic animals, but downregulated with insulin supplementation alone. Cotreatment with insulin and an ARB resulted in drastic increase in insulin-receptor density in the diabetic rats. In addition, expression of ETA-R in cardiomyocytes was upregulated and was consistently maintained within the various treatment modalities. However, ETB-R expression was significantly reduced in the diabetic group treated with both insulin and an ARB. The changes in the expression of the insulin, the ETA-Rs, and the ETB-Rs at the various sites of the myocardium and the effect of both insulin treatment and blockade of the AT1-R explain the new benefits related to the halting of myocardial remodeling in IDDM rats.

A two-year survey on mosquitoes of Lebanon

A total of 6,500 mosquitoes were identified during a two-year survey (1999-2001) in Lebanon, and these belonged to twelve species: Culex pipiens, Cx. laticinctus, Cx. mimeticus, Cx. hortensis, Cx. judaicus, Aedes aegypti, Ae. cretinus, Ochlerotatus caspius, Oc. geniculatus, Oc. pulchritarsis, Culiseta longiareolata and Anopheles claviger. Culex pipiens was the most predominant species in Lebanon, collected indoors and outdoors. It was continuously abundant and active throughout the year. Culex judaicus was a small and rare mosquito and it is reported to occur for the first time in Lebanon. On the coastal areas, Ochlerotatus caspius was very common, and proved to be a complex of species as two forms were detected. One of the vectors of malaria, Anopheles claviger, was collected from May to September, from eight sites in Lebanon. Its breeding sites were restricted to fresh, cool, and clean water in pools and wells. Most of these breeding sites were in the populated Metn County where a few indigenous cases of malaria were reported from 1997-2000. This shows that the reported malaria cases were not imported, but caused by the bites of locally infected Anopheles females.

Effect of insulin and angiotensin II receptor subtype-1 antagonist on myocardial remodelling in rats with insulin-dependent diabetes mellitus

OBJECTIVES

To assess the role of insulin or an angiotensin II receptor antagonist (losartan), or both, in preventing cardiomyocyte damage in rats suffering from insulin-dependent diabetes mellitus (IDDM), and to correlate it with insulin receptor modulation at the cardiomyocyte, coronary endothelium and skeletal muscle cell level.

DESIGN

Animals were divided into groups of normal rats, diabetic rats, and diabetic rats given insulin, each subdivided into a control group and an experimental group treated with losartan.

METHODS

The animals were killed 1 month after enrollment to the study. Perfusion of the heart with iodine-125-labelled insulin was carried out for all the groups and the binding kinetics of insulin to its receptors on the coronary endothelial cells and the cardiomyocytes were determined using a physical/mathematical model. In addition, tissue samples from the heart and intercostal skeletal muscle were snap frozen and used for histological, indirect immunofluorescence and western blot analysis.

RESULTS

Cardiac muscle from diabetic animals exhibited diffuse cardiomyopathic changes consisting of widespread vacuolation, loss of striation and cellular hypertrophy, which were reduced and even prevented by treatment with insulin and losartan. In addition, losartan seemed to mediate the upregulation of insulin receptor density on cardiomyocytes and skeletal muscle, and increase insulin receptor affinity at the coronary endothelial site. Finally, treatment with losartan induced a significant decrease in glucose concentrations in the diabetic group compared with the appropriate controls.

CONCLUSIONS

Addition of losartan to the standard insulin treatment in non-hypertensive animals with IDDM offers new benefits concerning cardiac protection and prevention of damage. This may be attributed, in part, to insulin receptor density and sensitization.

Identification of Lebanese dermotropic putative Leishmania archibaldi isolates by gp63 PCR-RFLP

Leishmania stocks isolated from cutaneous lesions in Lebanon were characterized by PCR methods. The stocks were typed as putative L. (L.) archibaldi (gp63 PCR-RFLP), belonging to 2 different genotypes (PCR-based schizodeme analysis). This constitutes the first report on the presence of L. (L.) archibaldi in the Middle East.

Isoenzyme characterization of Leishmania isolates from Lebanon and Syria

Leishmania parasites were isolated from 22 Lebanese and 5 Syrian patients with active skin lesions for whom the diagnosis was confirmed by histopathological examination. The isolates were characterized by starch gel electrophoresis and analysis of 13 enzyme systems. Eight Old-World reference strains were used for comparison. One Syrian isolate belonged to Leishmania major, and four Syrian and two Lebanese to Leishmania tropica. Contrary to expectations, the majority of Lebanese isolates were related to the Leishmania donovani complex, and more particularly Leishmania infantum.

Gp63 gene polymorphism and population structure of Leishmania donovani complex: influence of the host selection pressure?

The gp63 encoding genes were characterized by PCR-RFLP in 35 isolates representative of the Leishmania donovani complex (L. infantum, L. donovani, L. archibaldi and L. chagasi), with special attention to Mediterranean L. infantum from different geographical origins, and in separate groups from Old World Leishmania (L. major, L. tropica and L. aethiopica). The aim was to evaluate how the possible selective pressure by the host on these important surface proteins would influence structuring of our sample. Comparison was carried out with the structure obtained (i) from reported isoenzyme data, characters supposed to vary neutrally, and (ii) from PCR-RFLP analysis of gp63 inter-genic regions, containing nontranslated spacers and regulatory genes. Polymorphism within the gp63-encoding region, was much higher than in gp63 inter-genic regions. In the gp63 intra-genic dendrogram, the 4 species of L. donovani complex were discriminated and quite distinct from outgroups. Within L. infantum, geographical structuring was observed and did not overlap with the structure built-up from isoenzymes and inter-genic data. These results support the idea of a strong host-selection on gp63, at vector level but most of all at vertebrate (human or dog) immunological level. Furthermore, they illustrate how the nature of genetic characters may influence the perception of population structuring.

Aspergillus vertebral osteomyelitis in a child with a primary monocyte killing defect: response to GM-CSF therapy

We report the first case of vertebral aspergillosis in a child with a primary defect in monocyte killing, an extremely rare immunodeficiency The diagnosis of defective monocyte killing was made by an in vitro assay that showed normal killing of Staphylococcus aureus by the patient's neutrophils but impaired killing by his monocytes. Importantly, the extensive granulomatous infection that involved the vertebral column, posterior mediastinum, pleura, and lung was not responsive to aggressive treatment with a combination of liposomal amphotericin B. intralesional amphotericin B. itraconazole, and granulocyte transfusions. Dramatic clinical and radiological improvement was only seen after the addition of granulocyte macrophage-colony stimulating factor (GM-CSF) to his treatment regimen. The use of GM-CSF in the treatment of invasive aspergillosis in immunocompromised patients requires further evaluation.

The epidemiology of leishmaniases in Lebanon

The prevalence of leishmaniasis in Lebanon was studied in 1993-97 for a Lebanese population sample of about 81,000 subjects (60% rural and 40% urban) constituting roughly 3.4% of the total population. The prevalence of cutaneous leishmaniasis was found to be 0.18% in the rural versus 0.41% in the urban areas. Visceral leishmaniasis was practically non-existent in both environments. In addition, skin tests were done and anti-Leishmania antibodies were sought in a sample of the population at risk in the rural area. Skin tests were positive in 2.5% of the tested subjects, and 1% of the normal population had elevated levels of anti-Leishmania antibodies. The difference between the prevalence of clinical disease and positive skin testing and/or antibodies may be due to the existence of past or present subclinical disease. An unexpected finding was that the prevalent dermotropic parasite in Lebanon belongs to the L. donovani complex. Further characterization of the isolates by molecular techniques and definition of the transmission cycle of this parasite may explain our epidemiological findings.

Leishmania donovani invasion of the blood in a child with dermal leishmaniasis

Cutaneous leishmaniasis is highly endemic in eastern Mediterranean countries. The causative organisms are Leishmania tropica or Leishmania major but, further west, variants of Leishmania infantum frequently cause cutaneous leishmaniasis. We report a young girl from Beirut with an acute cutaneous leishmaniasis in whom the causative organism was cultured from both the skin lesion and the blood in the absence of any signs or symptoms typical of systemic involvement. The parasite was found to have a zymodeme typical of organisms belonging to the L. donovani complex. With the negative past history and in the absence of anti-Leishmania antibodies in her serum, post-kala-azar dermal leishmaniasis is an unlikely possibility, especially in view of the rarity of the complication in this part of the world. The infection was probably acquired during a recent visit to Aleppo, where cutaneous leishmaniasis is hyperendemic as similar cases have not been reported in Beirut. This case indicates the need to consider L. infantum strains in addition to L. tropica in cutaneous disease in Aleppo. This case also demonstrates that L. infantum can spread by the haematogenous route, even in a child without evidence of the immunosuppression, which usually predisposes to such spread.

Behavior in a mouse model of isolates of Leishmania donovani sensu lato cultured from the blood of patients with chronic cutaneous lesions

Our objective was to characterize biologically in an animal model two isolates of Leishmania parasites unexpectedly encountered in the circulating blood of two patients with chronic cutaneous leishmaniasis. Both isolates were classified by cellulose acetate electrophoresis as belonging to the L. donovani senso lato complex. We elected to use BALB/c mice, an inbred strain that has been proven to be very sensitive to the dermotropic parasite L. major. This study demonstrated that for the same number of parasites, the course of infection with the L. donovani strain was different from that developed in similar animals that received the L. major strain. After a protracted incubation period, L. donovani produced scanty cutaneous lesions and mainly a systemic disease. This is in contrast to the rapidly spreading skin lesion that kills L. major-infected animals within a few months. It is concluded that BALB/c mice are an adequate animal model for the L. donovani strain, which had an unusual clinical presentation in humans. The prolonged incubation period, such as observed here, may lead to erroneous conclusions of host resistance if the experiment were terminated based on L. major activity in the same model. Finally, the unusual behavior in humans and mice of certain strains (such as the one encountered in these patients) must reflect peculiar intrinsic features of the parasite, which are best understood using animal models in the laboratory.

Recurrent molar pregnancies in a family with extensive intermarriage: report of a family and review of the literature

BACKGROUND

Familial recurrent molar pregnancies are exceedingly rare. The genetic basis for recurrent moles is not well understood, and its association with major human lymphocytic antigen histocompatibility is debatable. The purpose of this report is to present a family with extensive intermarriage and recurrent molar pregnancies with some emphasis on the result of the human lymphocytic antigen-typing.

CASE

Two sisters, both married to first-degree cousins, had three and five pathologically confirmed molar pregnancies, respectively. A second-degree cousin, also married to her first-degree cousin, is also reported to have had five consecutive moles. Chromosomal analysis and human lymphocytic antigen-typing on the two sisters and their spouses was performed. Human lymphocytic antigen-typing was compared to a cross-sectional sample of our population. This showed a high incidence of unusual human lymphocytic antigens in these family members.

CONCLUSION

In families with extensive intermarriage and recurrent molar pregnancies, patients and their spouses may have unusual human lymphocytic antigen histocompatibility, which supports the possibility of a strong genetic predisposition expressed at the level of major histocompatibility class I and II gene translation.

Identification of Leishmania isolates from a Lebanese population

We report the results of enzymatic patterns of isolates of Leishmania cultured from patients referred to Department of Dermatology of the American University of Beirut Medical Center in Lebanon. The results reveal that these Lebanese isolates are all very similar despite variable clinical presentations of the patients and differences in geographic origin. Leishmania donovani sensu lato is the dominant species present in the skin lesions observed; thus, clinical manifestations and/or geographic distribution cannot be used as reliable criteria for identifying Leishmania parasites from this geographic area. Enzyme data should be combined with these parameters before definitive identification can be made.

Chronic cutaneous leishmaniasis: Leishmania parasites in blood

Two patients with chronic cutaneous leishmaniasis had positive blood cultures. The diagnosis was established by the clinical picture, skin biopsy, and culture for Leishmania major and tropica.

Hematologic parameters and iron stores in patients on hemodialysis for chronic renal failure

Thirty-two patients on hemodialysis for chronic renal failure were investigated. A correlation was sought between bone marrow iron stores assessed on Prussian-blue stained smears, and some common hematological parameters such as red blood corpuscle indexes obtained by coulter counter, serum iron, iron-binding capacity and serum ferritin levels (measured by RIA). MCH and MCV were both found significantly depressed in patients with depleted iron stores, a situation not reflected by any of the other tested parameters. These results reveal a practical and simple guideline for the treating practitioner who wants to initiate iron supplementation or withdrawal in these patients especially in areas where more elaborate tests may not be at hand.

Functional and structural changes in the jejunum of the rat following cysteamine and stress-induced duodenal ulcer

The effects of cysteamine and stress-induced duodenal ulcer on the functional and structural properties of the rat jejunum were investigated. The absorptive capacity of the jejunum was determined using alanine as the permeant solute and the single-pass perfusion technique. A statistically significant decrease (p < 0.01) in alanine absorption was observed after 8 h and 3 days of duodenal ulcer induction by stress and cysteamine respectively. However, alanine transport measured 7 days after cysteamine or stress ulcer induction showed no significant change from control values. Cysteamine and stress-induced duodenal ulcer did not show any significant change in water absorption across the jejunum when measured after 8 h, 3 and 7 days of ulcer induction. Microscopically, the jejunum of rats with 3-day cysteamine-induced ulcer exhibited diffuse type of apical derangements with excessive swelling of the villi and progressive degenerative changes. No such changes were noticed on the 7th day nor in the jejunum of the rats with stress-induced duodenal ulcer. The results suggest that cysteamine-induced duodenal ulcer produces an inhibition in the absorptive capacity of the jejunum which is time-dependent and reversible.

Blood leukocyte contribution to serum ferritin levels in patients on chronic hemodialysis

Serum ferritin level has been shown by many investigators to be a good indicator of bone marrow iron stores in normal subjects. Although this correlation may hold in some pathological situations, it is lost in others. In leukemia a dissociation has been observed between serum ferritin levels and bone marrow iron stores. Leukemic cells were demonstrated to contain high levels of ferritin and to secrete it in the serum, causing this dissociation. In this study we investigated the possibility of having an analogous situation in patients on chronic hemodialysis. The latter patients have normal or high ferritin levels irrespective of bone marrow iron stores. Our results show that blood neutrophils and lymphocytes do not contribute to the high serum ferritin levels in these patients. Ferritin level in blood monocytes, however, was found to correlate with the serum ferritin levels and bone marrow iron stores in dialysis patients. Hence we concluded that sources other than blood leukocytes must be contributing to the high serum ferritin level in these patients. On the other hand, to unravel the role played in these changes by the monocytic cell population requires dynamic studies.

Colchicine inhibition of duodenal absorption of calcium

1. The effect of colchicine on calcium absorption across rat duodenum has been investigated using the single-pass continuous perfusion technique and the two-compartment system model. 2. Perfusing the rat duodenum with 0.1 and 0.5 mM colchicine produced a dose-dependent inhibiting pattern of calcium transport with no effect noted for water transport. 3. Colchicine at 0.5 mM caused a significant decrease in the rate of calcium uptake and in the accumulation capacity of the duodenal cells. 4. Accumulation of calcium in the duodenal strips displayed saturation kinetics with increasing concentration of calcium in the incubation medium. Colchicine at 0.5 mM showed a lower saturation level and decreased the average maximal flux around 46%.

Vitamin D suppression of spleen colony formation in radiation chimeras

The effect of vitamin D on spleen colonies in murine bone marrow chimeras was investigated using a single suprapharmacologic dose of vitamin D. The results revealed that vitamin D even without producing hypercalcemia, reduced to a significant degree the number of spleen colonies obtained. This finding is thought to be due to either a direct effect of the vitamin on the capacity of stem cells to multiply or an effect on the number of stem cells that lodge in the spleen.

Monocyte ferritin as a possible index of bone marrow iron stores in patients on chronic hemodialysis

It is well known that macrophages are the principle cells responsible for removal of senescent erythrocytes from circulation and are the major storage cell for body iron. Monitoring stored iron in patients with anemia secondary to renal failure and chronic hemodialysis is an important parameter used for gauging supplementing these patients with iron. We have proven that blood monocyte ferritin unlike serum ferritin reflects adequately bone marrow iron stores and thus replaces an undesirable procedure in such patients namely bone marrow punctures.

Immunologic and anti-immunosuppressive effects of vitamin A

The effects of vitamin A alcohol on cell-mediated immunity in vitro and its ability to prevent the immunosuppressive effects of prednisolone and cyclophosphamide in vivo were studied in mice. Lymphocytes from Calmette-Guérin bacillus (BCG) sensitized mice were stimulated specifically with purified protein derivative (PPD) and nonspecifically with phytohemagglutinin (PHA). In the vitamin A injected animals there was significant enhancement of the spleen lymphocyte transformation not only in the PPD-sensitive cells but also in the T cells at large. In addition, vitamin A was able to restore to normal the cellular and humoral forms of immunity in prednisolone and cyclophosphamide-treated animals. It is suggested that vitamin A in nontoxic doses may have a role in enhancing the responses to weak immunogens and in reversing immunosuppression.

Thyrotropin secreting pituitary tumours: a cause of hyperthyroidism

Pituitary thyrotropin excess resulting in hyperthyroidism has been previously reported in only 25 patients, of whom 19 had a pituitary tumour. This report describes a patient in whom a thyrotropin-producing pituitary tumour was associated with triiodothyronine thyrotoxicosis. Hypophysectomy was followed by a prompt fall in serum thyrotropin and a return to a euthyroid state.

The role of the macrophage in cutaneous leishmaniasis

The investigation of the role of the macrophage in cutaneous leishmaniasis has been prompted by observations of the clinical behaviour of the infection. In contrast to the self-healing oriental sore, chronic leishmaniasis is characterized by persistent lesions and leishmania recidiva by lesions that flare up locally long after clinical healing. In both clinical types, the parasite is thought to be maintained inside the macrophages. It will be shown that the normal macrophages of mice and guinea-pigs are parasitized by L. tropica; the parasite is not killed by the macrophages but it multiplies within these cells. Incubation of the macrophages with rabbit or human anti-Leishmania sera on the other hand, leads to the attachment of specific immunoglobulins to the macrophage cell surface and consequently to the prevention of parasitization by L. tropica under the experimental conditions. The parasite appears to be immobilized at the macrophage cell surface. Normal rabbit or human sera did not interfere with parasitization. It is postulated that the parasite specifically immobilized at the cell surface might possibly be better exposed to and affected by the immune response than intracellular parasites. Furthermore, infected parasitized macrophages contribute to the immune response by processing soluble antigens from the intracellular parasites and presenting them on their surfaces, as seen by the greater affinity (higher dilution) of anti-Leishmania antibody for the cell membrane of infected macrophages than for normal macrophages.