Modulation of macrophage C3b receptor function by cytochalasin-sensitive structures

A quantitative rosette assay was employed in order to determine if through pharmacologic probes we could gain an insight into the nature of the interaction between C3b-coated particles and the macrophage C3b receptor. Rabbit alveolar macrophage monolayers were challenged with chromium-labeled, complement-coated (via cold agglutinin) human erythrocytes (HEC3b) and the per cent of bound counts determined in the distilled water lysate. With this assay system in which ingestion is negligible, the cytochalasins (A greater than E greater than D greater than B) produced the most marked inhibition of rosette formation compared to control treated monolayers. No agent examined produced consistent augmentation. Cytochalasin A at 10(-5), 10(-6), and 10(-7) M inhibited rosette formation by 77+/- 2, 44 +/- 4 and 15 +/- 7 (S.E.), per cent, respectively. Cytochalasin E was also markedly inhibitory, Cytochalasins B and D produced approximately 30% inhibition at 10(-5) M. The cytochalasin effect was not secondary to an interaction between these agents and complement-sensitized erythrocytes, although cytochalasin E was also able to reduce erythrocyte-bouund C3b reactivity. Cytochalasin A and E modulation of the macrophage C3b reactivity occurred within a few minutes and was only slightly reversible. Cytochalasins A and E could also disrupt performed rosettes but the effect was not as pronounced as when these agents were present before and/or during the actual adherence phenomenon. Vinblastine and colchicine (10(-5) and 10(-6) M) also produced significant inhibition of rosette formation, although the magnitude of the effect was less than that for cytochalasins A and E. Further characterization of the vinblastine and colchicine effect demonstrated that the inhibition was rapid, irreversible over a 60-min incubation, and not explained by an alteration in macrophage attachment or in HEC3b reactivity. Agents producing insignificant inhibition of rosette formation included the following: dibutyryl cAMP and cAMP agonists (PGE1, theophylline), 8-bromo cGMP and cGMP agonists (carbachol, asorbic acid), dimethylsulfoxide, heparin, ethanol, dextran sulfate, DEAE-dextran, and poly-L-lysine. The data suggest that cytochalasin, vinblastine and colchicine sensitive membrane structures, most likely microfilaments and microtubules, are important in the interaction of C3b-coated particles with the macrophage C3b receptor.     

Clinical Evaluation of a Rosette Inhibition Test in Renal Allotransplantation

The formation of spontaneous rosettes by peripheral blood or spleen mononuclear cells when incubated with sheep red blood cells has proved a useful way of assessing the potency of immunosuppressive drugs and antilymphocyte sera in vitro. A test employing the inhibition by antilymphocyte globulin (A.L.G.) of spontaneous rosette formation around peripheral blood mononuclear cells is described. This has been used to assess the degree of immunosuppression in patients with renal allografts and uraemic patients on regular haemodialysis.Twenty-three patients with renal allografts had 21 clinically diagnosed episodes of rejection. In none of these rejection episodes was the minimal inhibitory concentration (M.I.C.) of A.L.G. (that necessary to reduce the spontaneous rosette formation of peripheral cells by 75%) less than 1/50,000. Nineteen patients had no rejection episodes during 57 patient/months of continuous observation while the M.I.C. was at a greater dilution than 1/50,000. The test has therefore been of great value in suggesting when an individual is capable of rejecting his graft, and allows the dose of immunosuppressive drugs to be adjusted to a minimum in a controlled fashion. It has been of use in diagnosing rejection in the anuric patient, when the distinction between rejection, urinary tract obstruction, and infection is particularly difficult.Fifteen patients maintained on regular haemodialysis for more than a year had, as judged by this technique, less reactive lymphocytes than normal healthy controls. The degree of immunosuppression was not as great as in the patients on full immunosuppressive regimens.     

Isoform-specific regulation of immune cell reactivity by the catalytic subunit of protein kinase A (PKA)

There are two major genes encoding the catalytic subunits of protein kinase A, Cα and Cβ. The functional significance of these isoforms is enigmatic. Lymphoid cells of the immune system express both Cα and Cβ. In this study we tested the role of Cα and Cβ in regulating immune cell reactivity to antigens using mice carrying a targeted disruption of the Cα and Cβ gene respectively. Cα and Cβ ablation both resulted in a 50% reduction in PKA-specific kinase activity and the level of PKA type I but not PKA type II. Moreover, despite that C subunit ablation did not affect immune cell development and homeostasis, Cα but not Cβ ablation augmented expression of the activation marker CD69 on lymphocytes. CD69 induction coincided with immune cell hyperresponsiveness and was associated with reduced sensitivity to cAMP-mediated inhibition of anti-CD3 induced T cell proliferation. Our results imply that Cα is required for normal immune cell reactivity and demonstrates isoform-specific effects and non-redundant functions of C subunit isoforms expressed in the same cell.     

Cellular immunity in patients with malignant melanoma and their household contacts

Summary Immune reactivity was measured in control subjects and in 86 patients with malignant melanoma using four tests of cellular immunity. In addition, cellular immune reactivity to melanoma extract was studied in 13 household contacts of patients with melanoma. Thirty percent (4/13) of the household contacts showed reactivity to melanoma extract as determined by lymphocyte stimulation as compared to 20% of patients and 5% of controls. Seventy-two percent (8/11) household contacts showed reactivity as measured by the indirect MIF test, compared to 38% of patients and 23% of normal controls. As determined by the leukocyte migration inhibition test, 71% (5/7) of household contacts showed reactivity to melanoma extract versus 20% of patients and 22% of controls. The number of household contacts studied was low; however, it was observed that these subjects showed responses to melanoma extract with considerably greater frequency than did normal control subjects, and the frequency of positive responses in patients with melanoma was intermediate between that of the household contacts and the normal controls.This work was supported in part by grants AI-10495, AI CA-10686, and CA 13671 from the U.S. Public Health Service. Dr. Spitler is supported by a National Institutes of Health Career Development Award (AI-43012).     

Evaluation of Rosette Inhibition Test in Renal Transplantation

Serial rosette inhibition tests were performed on 11 renal transplant patients in an attempt to predict graft rejection. The rosette inhibition titre was higher in immunosuppressed patients than in normal subjects. The test was of predictive value in only two out of 12 rejection episodes, where a fall in titre to normal levels occurred 48 hours and 24 hours, respectively, before biochemical evidence of rejection. In two further rejection episodes the titre fell at the time of rejection. The titre changes in all tests were small and there were frequent inconsistencies in the results of individual tests. A study of the variables was undertaken, with standardization of the technique, and improvements were made in reading the test. Despite these changes the test was still not sufficiently accurate or reliable to be used as the basis of treatment of rejection episodes.     

Cellular hypersensitivity to human pancreatic B-cell clone in diabetes mellitus and its relationship to the presence of islet cell antibodies

A leukocyte migration inhibition test on the human pancreatic B-cell clone (JHPI-1) was performed in 13 IDDM patients with islet cell cytoplasmic antibody (ICCA) and/or islet cell surface antibody (ICSA), 15 IDDM patients without ICCA or ICSA, 34 NIDDM patients and 17 healthy controls. The mean values for the migration index (M.I. %) in each group were 85.4 +/- 6.9, 89.1 +/- 10.9, 98.3 +/- 7.9 and 100.0 +/- 8.5. The M.I. values were significantly decreased in IDDM patients than in NIDDM patients and controls irrespective of whether or not there were islet cell antibodies in the patients' sera. When M.I. values less than 0.83 (Mean-2 S.D.) were taken as indicative of inhibition, the percentage of IDDM and NIDDM patients with migration inhibition were 32% and 0% respectively. And the decreased M.I. values in IDDM patients proved not to be due to non-specific migration inhibition by normal M.I. values, with the human fetal lung fibroblast cells (W 138) as antigen. Our data suggested that the lymphocytes of IDDM patients might be sensitized by pancreatic B-cell antigen(s) present in the JHPI-1 cells, which promoted leukocyte migration inhibition. No correlation between the migration indices and duration of diabetes mellitus in IDDM patients was observed (r = 0.254, Y = 84.9 + 0.49 X). LMT to JHPI-1 seems to be useful in detecting the abnormal cell-mediated immunity even in patients with longstanding IDDM.     

Modulation of Ia-like antigen expression and antigen-presenting activity of human monocytes by endotoxin and zymosan A

The environmental agents E. coli endotoxin and zymosan A modulated antigen-specific T cell proliferation in vitro, assessed by 3H-TdR uptake. In the continual presence of these agents, human mononuclear leukocyte responses to the antigens tuberculin PPD, Candida albicans, and mumps were significantly reduced. Treatment of adherent cell-depleted T cells with the agents did not affect their subsequent reactivity to soluble antigens in the presence of normal M phi. However, cultures consisting of pretreated M phi, normal T cells, and soluble antigen gave responses that were only 7 to 38% of control values, indicating that the function of the antigen-presenting cell, not the T cell, was inhibited. This effect was observed only when treatment with endotoxin or zymosan A preceded antigen stimulation by at least 24 hr, suggesting that a gradual inhibition of antigen presentation had occurred. When various ratios of normal antigen-pulsed and agent-treated M phi were cultured with normal T cells, antigen-specific responses were not significantly different from control cultures; this indicated that M phi-mediated suppression was not involved. It did not appear that the inhibition was due to enhanced antigen degradation by the treated M phi because responses were not reconstituted in the presence of excess antigen. After endotoxin or zymosan A treatment of the M phi population the proportion of Ia+ cells was reduced significantly, and surface expression of Ia antigen correlated with the ability of the cell population to present antigens to immune T cells. This suggested that endotoxin and zymosan A induce a loss of surface Ia antigen on antigen-presenting cells that inhibits immune T cell activation.     

Effects of a Cardio-selective Beta-adrenergic Blocker (I.C.I. 50172) at Exercise in Angina Pectoris

A cardio-selective beta-adrenergic blocking agent (I.C.I. 50172), which has been studied both in normal subjects and in patients with angina pectoris during and after a standardized work test, produced a significant increase in the exercise tolerance of the patients. These favourable effects are comparable with those of propranolol.One patient with severe bronchial asthma and coronary insufficiency treated with I.C.I. 50172 improved and his respiratory function was not impaired.     

Enhanced regulatory T cell activity is an element of the host response to injury

CD4+CD25+ regulatory T cells (Tregs) play a critical role in suppressing the development of autoimmune disease, in controlling potentially harmful inflammatory responses, and in maintaining immune homeostasis. Because severe injury triggers both excessive inflammation and suppressed adaptive immunity, we wished to test whether injury could influence Treg activity. Using a mouse burn injury model, we demonstrate that injury significantly enhances Treg function. This increase in Treg activity is apparent at 7 days after injury and is restricted to lymph node CD4+CD25+ T cells draining the injury site. Moreover, we show that this injury-induced increase in Treg activity is cell-contact dependent and is mediated in part by increased cell surface TGF-beta1 expression. To test the in vivo significance of these findings, mice were depleted of CD4+CD25+ T cells before sham or burn injury and then were immunized to follow the development of T cell-dependent Ag-specific immune reactivity. We observed that injured mice, which normally demonstrate suppressed Th1-type immunity, showed normal Th1 responses when depleted of CD4+CD25+ T cells. Taken together, these observations suggest that injury can induce or amplify CD4+CD25+ Treg function and that CD4+CD25+ T cells contribute to the development of postinjury immune suppression.     

Enhancement of early human E rosette formation by cholinergic stimuli.

The effects of the cholinergic stimuli carbamylcholine (carbachol) and dibutyrl cyclic guanosine monophosphate (DBCGMP) were determined on both 'early' and 'total' E rosette formation. Ficoll-Hypaque-separated lymphocytes were preincubated with either carbachol or DBCGMP over a 10(-3) M to 10(-13) M dose range. Both agents significantly enhanced 'early', but not 'total' E rosette formation. Peak enhancement above control values occurred at 10(-7) M (72%) and 10(-9) M (69%) for carbachol and 10(-5) M (70%) and 10(-7) M (70%) for DBCGMP. Kinetic studies showed a rapid onset of enhancement (2.5 min) for carbachol, whereas DBCGMP required 15 min for significant enhancement to occur. The muscurinic nature of carbachol enhancement of E rosettes was demonstrated. Atropine at 10(-7) M completely abolished the carbachol effect while showing little inhibition of the DBCGMP effect on rosette formation. These studies indicate that the cholinergic stimuli carbachl and DBCGMP significantly enhance the 'early' E rosette former in man. Human T lymphocytes appear to have functional cholinergic receptors that can be blocked by the muscurinic antagonist atropine. The role of the cyclic nucleotides and their stimulants on the immune system is incompletely understood, but it would appear that they are extremely important in the differentiation and function of the T lymphocyte. E rosette formation may be a useful model in man for studying the effects of the cyclic nucleotides on the human T lymphocyte.     

Lymphocyte proliferative response to <Emphasis Type="Italic">Helicobacter pylori</Emphasis> antigens in <Emphasis Type="Italic">H. pylori</Emphasis>-infected patients

Helicobacter pylori (Hp) contributes to the development of gastric and extra-gastric diseases such as autoimmune thyroiditis (AT), and causes persistent life-long infection despite local and systemic immune response. We determined the specific cellular immune response to Hp antigens and PWM (control mitogen) in two groups of Hp infected patients - group A (n = 21), involving patients with autoimmune thyroiditis and group B (n = 13) of patients without AT - using modified lymphocyte transformation test before and after eradication therapy in comparison with healthy controls (group C, n = 15). Immune reactivity to the majority of Hp antigens (aHp, hHp, HpAg, CagA) was significantly lower in group B before eradication therapy in comparison with healthy Hp negative controls. A significant increase in immune reactivity was observed in group B to certain Hp antigens after successful eradication. The same levels (but insignificant) of immune reactivity were shown in group A. Our results indicate that Hp can cause the inhibition of the specific cellular immune response in Hp infected patients with or without autoimmune diseases such as AT, which can be abrogated by successful eradication of Hp. Lymphocyte transformation test appears to be a good tool for detection of immune memory cellular response in patients with Hp infection.     

Interrelation of immune and mediator lymphocyte receptors in mice

A study was made of the action of a specific muscarinic antagonist 3H-quinuclidinyl benzylate on the immune rosette formation in BALB/c mice. It was shown that treatment of mouse spleen lymphocytes by 3H-QNB at a concentration of 10(-9) M-10(-14) M brought about rosette formation inhibition. The process was dose-dependent. Atropine reversed the action of 3H-QNB.     

Increased burn-induced immunosuppression in lipopolysaccharide-resistant mice

Severe burns induce a state of immunosuppression, and the inflammatory response after burn injury may play a role in this phenomenon. This study examined the effect of the inflammatory response to endotoxin on burn-induced immunosuppression and oxidative stress. An endotoxin-resistant mouse strain (C3H/HeJ) and a normally responding mouse strain (C3H/HeN) were compared. The mice were separated into three groups of five animals for each experimental day: (1) saline, (2) buprenorphine, and (3) buprenorphine and 20% total body surface area burn. All animals were fed ad libitum. The inflammatory response was studied at 1, 4, 7, 10, and 14 days postburn. Proliferation of activated splenocytes in burn mice was significantly lower on days 7, 10, and 14 for the C3H/HeJ strain and on days 4 and 10 for the C3H/HeN strain. Globally, C3H/HeJ presented stronger immune suppression than C3H/HeN. Oxidative stress parameters (liver malonaldehyde, spleen metabolic activity, and thiol concentrations) were higher in endotoxin-resistant mice than in the control strain. Impairment of the inflammatory response was more pronounced and oxidative stress was greater in endotoxin-resistant burn mice than in normal burn controls. Buprenorphine administration was not related to depression of these immune parameters. The inflammatory response following burn injury may be beneficial to the immune system.     

Detection of masked anti-DNA antibodies in lupus sera by a monoclonal anti-idiotype

We report here the use of a monoclonal anti-idiotype 3I to human anti-DNA antibodies to detect in serum idiotype-positive antigen-binding antibodies lacking DNA-binding activity as measured by conventional antigen binding assays. We studied paired serum samples from 13 patients with systemic lupus obtained at two times in the course of their disease: in each patient, one serum sample has anti-DNA activity and the second serum sample has no anti-dsDNA activity detectable by Millipore filter, ELISA, or Crithidia assay. Reactivity with 3I as detected with a radioimmunoassay (RIA) was present in all 13 sera with anti-dsDNA activity. Six patients showed a decrease in 3I reactivity to normal levels in the second serum sample, in which anti-dsDNA antibodies were not detectable by conventional antigen-binding assays. The other seven patients' second serum sample continued to show elevated 3I reactivity by RIA even though no anti-dsDNA activity was apparent. When the 3I-reactive antibodies from these latter patients' sera were eluted from a 3I affinity column, they revealed DNA-binding activity. Furthermore, dsDNA binding by these sera was apparent when they were displayed on Western blots of isoelectric focusing gels run in 8 M urea and incubated with radiolabeled dsDNA. These results indicate that the 3I anti-idiotype can detect anti-DNA antibodies in some sera of SLE patients that lack anti-DNA activity by ordinary assays. These antibodies may be inhibited in binding dsDNA by excess antigen or autologous anti-idiotype, and their DNA binding activity can be unmasked by procedures promoting immune complex dissociation.     

分枝杆菌L型感染与肺癌患者红细胞免疫功能改变的相关性

目的:研究分枝杆菌L型血行感染与肺癌患者红细胞免疫功能改变的相关性.方法:溶血离心培养法和滴片法检测血液中的分枝杆菌L型,常规方法测定红细胞沉降率(ESR)、红细胞C3b受体花环率(C3bRR)、免疫复合物花环率(ICRR)、血清红细胞C3b受体花环促进率(RFER)和抑制率(RFIR).结果:TBL( )与TBL(-)肺癌患者相比,C3bRR和ICRR两项指标均明显降低.TBL( )肺癌与TBL(-)肺癌患者相比,ESR增快更为显著.TBL(-)较TBL( )之RFER值的降低更为明显.RFIR差异未见有显著性.结论:分枝杆菌L型血行感染影响肺癌患者血沉和红细胞免疫功能改变.     

Control of C1 activation by nascent C3b and C4b: a mechanism of feedback inhibition

We have demonstrated that immune complexes turn over C1, i.e., limiting quantities of immune complexes activate an excess of C1. This was readily apparent in a system of purified C1 and C1-inhibitor (C1-In) but not in normal human serum (NHS). The following results indicate that C3 and C4 are the serum factors responsible for the inhibition of C1 turnover by immune complexes. 1) In a purified protein system composed of C1 and C1-In at pH 7.5, ionic strength 0.14 M, doses of immune complexes that activated all the C1 in 60 min at 37 degrees C yielded no detectable C1 activation when C2, C3, and C4 were also present. All proteins were at their physiologic concentrations. Activation was quantified by SDS-PAGE analysis and hemolytic titration 2) In order to inactivate C3 and C4, NHS was treated with 50 mM methylamine (MeAm) for 15 min at 37 degrees C, after which the MeAm was removed by dialysis. The activities of C1, C2, and C1-In were unaffected by this treatment. Doses of immune complexes that consumed no C1 in NHS, consumed all the C1 in MeAm-treated NHS (MeAm-NHS). 3) Reconstitution of MeAm-NHS with physiologic concentrations of C3 and C4 rendered the serum again resistant to excessive C1 consumption by immune complexes. Immune complexes used in these studies included EA-IgG, EA-IgM, tetanus-human anti-tetanus, and aggregated human IgG. There appeared to be specificity to the inhibition reaction since C4 by itself could inhibit C1 consumption by EA-IgM, whereas the presence of C3 was also required to control EA-IgG. Finally, N-acetyl-L-tyrosine was added to NHS at a final concentration of 30 mM. This nucleophile did not interact with native C3 or C4, nor did it directly activate C1. However, upon the addition of low doses of immune complexes, acetyl tyrosine did yield uncontrolled C1 activation, presumably by binding nascent C3b and C4b and thereby blocking their attachment to the immune complexes. We conclude that in NHS there is a mechanism of feedback inhibition by which nascent C3b and C4b inhibit C1 turnover by immune complexes. This mechanism of control might be physiologically important in that it prevents excessive complement activation by low concentrations of immune complexes.     

Studies on the production of anti-human-lymphocyte serum (ALS) in bulls]

The applicability of bulls as productive animals was considered for the preparation of anti-humans ALS. The course of immunologic response was studied by lymphoagglutination, lymphocytotoxicity, rosette inhibition, hemagglutination tests and by precipitin formation in two experimental groups immunized by different amounts of lymphocytes from peripheral blood of normal donors. The animals were found to respond well already after the second application of very small amounts of antigen (on day 0-4 times 10(7), on day 21-2 times 10(8) lymphocytes). They showed lymphoagglutination titre 1 : 512-2000, lymphocytotoxic titre being higher than 1 : 4000 and the rosette inhibition test gave a minimum titre of 1 : 65000. On the other hand, further application of a high amount of antigen (2 times 10(9), or 4 times 10(9) lymphocytes) did not lead to further increase in the titre; on the contrary - hyperimmunization resulted in a lower titre in the case of the rosette inhibition test, which is known to correlate best with the in vivo immunosuppressive activity. The hemagglutinin titre was also acceptable under the above conditions and the formation of undersirable precipitins against human serum proteins was negligible. Good response reached by a simple and economical immunization scheme speaks for the suitability of bulls for the production of ALS.     

Redistribution of the Fc receptor on human blood monocytes and peritoneal macrophages induced by immunoglobulin G-sensitized erythrocytes.

The Fc receptor is a plasma membrane component exhibiting an affinity for the C gamma 3 domain of certain subclasses of immunoglobulin G. Using anti-Rho (D)-sensitized red cells (EA) in a slide rosette technique, we have demonstrated a translational mobility and polar redistribution of this receptor on the human blood monocyte and peritoneal macrophage. These cells, isolated from venous blood and malignant ascites and identified histochemically, showed a time- and temperature-dependent receptor capping defined by binding six or more EA confined to the cell half-perimeter. Caps formed in serum were mainly extreme caps in which bound EA appeared as a morula contiguous with the adherent cell. At 21 degrees C and 37 degrees C in serum 80% live rosettes formed caps; virtually none formed at 4 degrees C and about 25% were seen in PBS at 21 degrees C. Similarly, 10% extreme caps in PBS and 60 and 70% in serum were seen at room temperature and 37 degrees C, respectively, suggesting a serum factor(s) was important in promoting live rosette capping. Capping was reversibly inhibited by sodium azide although inhibition was incomplete even at 0.1 M, a concentration 10-fold higher than that giving complete inhibition of lymphocyte antigen-receptor capping. Azide also induced reversion of capped rosettes to diffuse, noncapped rosettes, and to levels comparable to those seen in inhibition studies. Re-exposure to EA after rosette capping failed to increase either the proportion of cells forming rosettes or the fullness of such rosettes indicating a critical number of receptors had been capped. Live rosettes induced a spherocytosis in bound EA irrespective of capping status; such changes appeared early in PBS where capping was minimal. Dead cells bore EA as normal biconcave discs. Some rosetting EA were ultimately hemolyzed upon prolonged incubation, and erythrophagocytosis was seen in about 15% of capped rosettes at 37 degrees C.     

Assessment of three simple techniques for the screening of circulating immune complexes: Correlation with a parameter of complement consumption

The sera of 36 normal controls, 45 patients with various diseases and 11 pregnant women were screened for circulating immune complexes using three relatively simple and inexpensive techniques. These included inhibition of agglutination of IgG coated latex particles with a serum having rheumatoid factor activity, polyethylene glycol precipitation and anti-complementary activity test. The circulating immune complexes were detected in a significantly higher proportion of patients as compared to normal controls. In the patients, the presence of circulating immune complexes did not always correlate with clinically detectable immunoinflammatory tissue damage indicating that pathogenic as well as nonpathogenic immune complexes were being detected by the above mentioned techniques. The alpha-1-antitrypsin/C3 ratio, however, correlated well with clinically apparent immuno-inflammation.     

Microvascular reactivity in patients with hypercholesterolemia: effect of lipid lowering treatment

Impaired NO-dependent vasodilation of resistance vessels is an early marker of an increased risk of atherosclerosis; utility of the examination of microcirculation, however, is far less established. We have therefore tested the hypothesis that hypercholesterolemia is associated with an impaired microvascular reactivity and that this defect is at least partially reversible by lipid-lowering treatment. Twenty-seven otherwise healthy patients with severe hypercholesterolemia (HLP) were examined at rest and then after 10 weeks of atorvastatin treatment (20 mg/day). Skin microvascular reactivity (MVR) was examined by laser-Doppler flowmetry. Baseline MVR values of the studied group were compared to healthy control subjects, HLP patients with coronary artery disease (CAD) and diabetic patients with and without diabetic retinopathy. MVR was normal in HLP subjects without CAD. On the contrary, MVR was impaired in HLP patients with CAD. There was no effect of atorvastatin on MVR, despite the profound reduction of serum lipids. MVR values did not correlate with cholesterol levels. In diabetic subjects, the MVR was substantially impaired only in patients with retinopathy. In the subjects without retinopathy, MVR was either normal (type I diabetes) or moderately impaired (type II diabetes). MVR was thus normal in HLP patients without manifest vascular disease and was not influenced by lipid lowering therapy. Impairment in the MVR was only evident in subjects with HLP and severe CAD. These results suggest that microcirculation is not involved in the early vascular dysfunction induced by HLP and that MVR rather reflects changes which appear later in the course of the atherosclerotic disease.