[HLA class II in Mexican patients with pemphigus vulgaris: shared epitope for autoimmunity]. / HLA clase II en pacientes mexicanos con pénfigo vulgar: epítopo compartido para autoinmunidad.

INTRODUCTION: Pemphigus is an autoimmune blistering disease of skin and mucous membranes characterized by presence of IgG antibodies against desmoglein 3, and 1. Desmoglein 3 and 1 are presented in pemphigus vulgaris and pemphigus foliaceous, respectively. Desmoglein are transmembrane proteins that form part of cellular junctions called desmosomes. Major histocompatibility complex class II molecules have been related to autoimmune disease; in pemphigus vulgaris, different human lymphocyte antigens (HLA) were associated among different ethnic groups, such as HLA-DR4, HLA-DR14, and HLA-DR1. OBJECTIVE: to determine the allele HLA-DR genetic frequencies in Mexican patients with pemphigus. METHOD: Patients with clinical, histological, and immunofluorescence diagnosis monitored at the Dermatology Department of the Mexican General Hospital were included. DNA was extracted from blood samples and genetic recognition of HLA-DRß1 was performed by polymerase chain reaction and hybridization. Forty-three patients with pemphigus were included: 35 (81.4%) women and eight men (18.6%) between 16 and 85 years old. RESULTS: The HLA-DR14 and HLA-DR1 genetic frequencies were elevated among pemphigus patients and these alleles confer risk to pemphigus 2.2 and 3.3, respectively. CONCLUSION: These findings suggest that pemphigus vulgaris susceptibility is part of a general predisposition to present autoimmune diseases.

[HLA DRB1*, DQB1*, DPA1*, and DPB1* and their association with the pathogenesis of leukemia in the population of Venezuela]. / HLA DRB1*, DQB1*, DPA1* y DPB1* y su asociación con la patogénesis de las leucemias en población venezolana.

BACKGROUND: The HLA complex involved is a factor in the pathogenesis of leukemia. OBJECTIVES: The presence of class II HLA alleles DRB1 *, DQB1 *, DPA1 *, and DPB1 * was evaluated in 47 patients with acute lymphoblastic leukemia (ALL) and 48 with chronic myeloid leukemia (CML) for comparison with 48 healthy volunteers in Zulia, Venezuela, and to evaluate potential associations of HLA with leukemia. METHODS: Low- and high-resolution PCR-SSP was used for class II HLA regions DRB1 *, DQB1 *, DPA1 *, and DPB1 * following the instructions of KIT Olerup SSP Genovision. RESULTS: Alleles HLA-DRB1*14, especially DRB1*14:21, -DPA1*1:06, -DPA1*01:03,-DPA1*02:01, and the haplotypes HLA-DPA1*01:03-DPB1*04:01, DPA1*01:03-DPB1*02:01, DPA1*01:03-DPB1*99:01, -DRB1*14-DPA1*01:03, -DRB1*15-DPA1*01:03 were associated with CML (RR > 3); alleles HLA-DRB1*13, -DQB1*02, -DPA1*01:05, -DPA1*01:09 and the haplotypes HLA-DPA1*01:09-DPB1*02:01, DPA1*01:09-DPB1*04:01 were protective (RR < 1). Alleles HLA-DQB1*04, -DQB1*05, -DPA1*1:06, -DPA1*01:07, -DPA1*1:08 had a positive association with ALL. Alleles HLA-DPA1*01:09, -DPA1*02:01, -DPB1*02:01, -DPB1*03:01 and the haplotypes HLA-DPA1*01:03-DPB1*04:02, -DPA1*01:09-DPB1*02:01, -DPA1*01:09-DPB1*04:01, -DPA1*02:01-DPB1*04:02 were negatively associated. CONCLUSIONS: The other association patterns identified suggest marked differences in the pathogenesis of leukemia, which suggests possible deficiencies in antigen presentation for ALL or potential effects of molecular mimicry in CML.

Antecedentes: La presencia de HLA es un factor que influye en la patogénesis de las leucemias. Objetivos: Se evaluó la presencia de alelos HLA clase II DRB1*, DQB1*, DPA1* y DPB1* en 47 pacientes con leucemia linfoide aguda (LLA) y 48 con leucemia mieloide crónica (LMC), para compararlos con 48 voluntarios sanos de Zulia, Venezuela, y determinar las posibles asociaciones de HLA con las leucemias. Métodos: Se utilizó la técnica de PCR-SSP de baja y alta resolución para las regiones HLA clase II DRB1*, DQB1*, DPA1* y DPB1* conforme las instrucciones del KIT Olerup SSP Genovision. Resultados: Los alelos HLA-DRB1*14, especialmente DRB1*14:21, -DPA1*1:06, -DPA1*01:03,-DPA1*02:01, y los haplotipos HLA-DPA1*01:03-DPB1*04:01, DPA1*01:03-DPB1*02:01, DPA1*01:03-DPB1*99:01, -DRB1*14-DPA1*01:03, -DRB1*15-DPA1*01:03 tuvieron asociación con LMC (RR > 3); los alelos HLA-DRB1*13, -DQB1*02, -DPA1*01:05, -DPA1*01:09 y los haplotipos HLA-DPA1*01:09-DPB1*02:01, DPA1*01:09-DPB1*04:01 resultaron protectores (RR < 1). Los alelos HLA-DQB1*04, -DQB1*05, -DPA1*1:06, -DPA1*01:07, -DPA1*1:08 tuvieron asociación positiva con LLA. Los alelos HLA-DPA1*01:09, -DPA1*02:01, -DPB1*02:01, -DPB1*03:01 y los haplotipos HLA-DPA1*01:03-DPB1*04:02, -DPA1*01:09-DPB1*02:01, -DPA1*01:09-DPB1*04:01, -DPA1*02:01-DPB1*04:02 resultaron asociados negativamente. Conclusiones: La fuerte asociación de HLA DRB1*14 con la LMC y la ausencia de asociaciones DRB1* con LLA y los otros patrones de asociación identificados sugieren marcadas diferencias en las patogénesis de las leucemias, lo que orienta hacia posibles deficiencias en la presentación antigénica para LLA o posibles efectos de mimetismo molecular en LMC.

The association between the HLA-G 14-bp insertion/deletion polymorphism and type 1 diabetes.

Type 1 diabetes (T1D) is a multifactorial disease that has a strong genetic component. The HLA-G is a nonclassical HLA class I locus that is associated with immunomodulatory functions, including downregulation of innate and adaptive immune responses and induction of immune tolerance. However, there is currently limited information about the involvement of HLA-G in T1D susceptibility. This case-control study aims to investigate the T1D susceptibility association of alleles and genotypes of a widely investigated 14-bp insertion/deletion polymorphism in the HLA-G and to provide further evidence of the frequency distribution of class II HLA-DR-DQ-risk genotypes in T1D children and adolescents in the Brazilian population. The deletion allele and the homozygous deletion genotype are associated with susceptibility to T1D and the insertion allele and the heterozygous deletion/insertion genotype are associated with protection from T1D. We also confirm that genetic susceptibility to T1D is associated with the DRB1*03:01-DQA1*05:01-DQB1*02:01 and DRB1*04-DQA1*03:01-DQB1*03:02 haplotypes in Brazilian northeast region. The DR3-DQ2/DR4-DQ8 genotype conferred the highest detected risk for T1D. Our results identify a novel association of the 14-bp deletion allele and the homozygous deletion genotype with T1D development and provide additional evidence of the importance of HLA class II heterozygous DR3-DQ2/DR4-DQ8 genotype in T1D susceptibility.

Effects of two lipid lowering therapies on immune responses in hyperlipidemic subjects.

AIMS: To compare the effects of two of the most effective lipid-lowering therapies with similar LDL-cholesterol reduction capacity on the innate and adaptive immune responses through the evaluation of autoantibodies anti-oxidized LDL (anti-oxLDL Abs) and electronegative LDL [LDL(-)] levels. MAIN METHODS: We performed a prospective, randomized, open label study, with parallel arms and blinded endpoints. One hundred and twelve subjects completed the study protocol and received rosuvastatin 40 mg or ezetimibe/simvastatin 10/40 mg for 12 weeks. Lipids, apolipoproteins, LDL(-), and anti-oxLDL Abs (IgG) were assayed at baseline and end of study. KEY FINDINGS: Main clinical and laboratory characteristics were comparable at baseline. Lipid modifications were similar in both treatment arms, however, a significant raise in anti-oxLDL Abs levels was observed in subjects treated with rosuvastatin (p=0.026 vs. baseline), but not in those receiving simvastatin/ezetimibe. (p=0.233 vs. baseline), thus suggesting modulation of adaptive immunity by a potent statin. Titers of LDL(-) were not modified by the treatments. SIGNIFICANCE: Considering atherosclerosis as an immune disease, this study adds new information, showing that under similar LDL-cholesterol reduction, the choice of lipid-lowering therapy can differently modulate adaptive immune responses.

Impact of using different laboratory assays to detect human leukocyte antigen antibodies in female blood donors.

BACKGROUND: HLA antibodies passively transferred to transfused recipients may cause transfusion reactions such as transfusion-related acute lung injury (TRALI), but in many of the reported TRALI incidents, no white blood cell antibodies have been identified. We investigated whether a higher number of anti-HLA would be detected in donor's plasma by using a method with potential higher sensitivity rate. STUDY DESIGN AND METHODS: Sera from 300 previously pregnant female blood donors were screened for anti-HLA using a solid-phase mixed-antigen assay (enzyme-linked immunosorbent assay [ELISA]). Samples from 60 women with three or more pregnancies with a negative ELISA were further tested using microbead-flow assays (LABScreen mixed, panel-reactive antibodies [PRA], and single antigen). RESULTS: Anti-HLA Class I and/or Class II were detected by ELISA in 26.7% (80/300) of all women and in 37.0% (37/100) of women with three or more pregnancies. The LABScreen assays detected additional anti-HLA specificities (44 Class I and 17 Class II) in 28.3% (17/60) of ELISA-negative donors with three or more pregnancies. HLA antibodies were detected in 8.3% (5/60), 18.3% (11/60), and 21.7% (13/60) of ELISA-negative women by LABScreen mixed, PRA, or single antigen, respectively. CONCLUSION: Our data showed that the microbead-flow detected more HLA antibodies than ELISA, but the clinical significance of these antibodies is currently unknown. Detecting anti-HLA is useful for donor management and could contribute to the decision to definitively defer blood donors involved in TRALI incidents. However, further studies are necessary to better determinate the relative risk of TRALI induced by anti-HLA detected only by techniques with higher sensitivity rate.

Enfermedad celíaca y su patogenia / An update on the pathogenesis of celiac disease

Celiac disease (CD), with a 1 percent worldwide prevalence, is an enteropathy caused by an autoimmune reaction to gluten in genetically susceptible individuals, which codify for histocompatibility molecules HLA DQ-2/DQ-8. From the anatomical point of view, CD is characterized by intestinal villous atrophy, crypt hyperplasia, intraepithelial lymphocytosis (IELs) and leukocyte infiltration of the lamina propriety. Patients achieve a complete clinical and endoscopic remission with a gluten free diet. However, symptoms and anatomical alterations recur when this protein is reintroduced in the diet. The pathogenic mechanisms in this disease are not yet well understood, but it is clear that genetic, environmental and immunological factors play a role. The latter are the focus of this review, since this is the only autoimmune disease whose precipitating factor for immunological tissue damage is known.

[An update on the pathogenesis of celiac disease]. / Enfermedad celíaca y su patogenia.

Celiac disease (CD), with a 1% worldwide prevalence, is an enteropathy caused by an autoimmune reaction to gluten in genetically susceptible individuals, which codify for histocompatibility molecules HLA DQ-2/DQ-8. From the anatomical point of view, CD is characterized by intestinal villous atrophy, crypt hyperplasia, intraepithelial lymphocytosis (IELs) and leukocyte infiltration of the lamina propriety. Patients achieve a complete clinical and endoscopic remission with a gluten free diet. However, symptoms and anatomical alterations recur when this protein is reintroduced in the diet. The pathogenic mechanisms in this disease are not yet well understood, but it is clear that genetic, environmental and immunological factors play a role. The latter are the focus of this review, since this is the only autoimmune disease whose precipitating factor for immunological tissue damage is known.

[Comparative study between the Mitsuda test and the human leukocyte antigens in leprosy patients]. / Estudo comparativo entre reação de Mitsuda e antígenos leucocitários humanos em pacientes hansenianos.

In this study, we aimed to compare the Mitsuda skin test with the alleles HLA-DR2/HLA-DR3 and HLA-DQ1, in relation to the clinical forms of leprosy in 176 patients (50 TT, 50 LL and 76 B). The results obtained did not reveal any association between the Mitsuda reaction and the HLA alleles in the clinical forms isolated. However, when analyzed according to Mitsuda test response, a significant association was found between patients with negative Mitsuda reaction and HLA-DQ1 (p=0.002). No association was observed between positive Mitsuda reaction and the HLA-DR2/DR3 alleles. We concluded that the allele HLA-DQ1 has an important participation when there is no response to the Mitsuda test. We suggest that more specific studies should be developed on this allele.

Estudo comparativo entre reação de Mitsuda e antígenos leucocitários humanos em pacientes hansenianos / Comparative study between the Mitsuda test and the human leukocyte antigens in leprosy patients

Neste estudo, propomos comparar o teste cutâneo de Mitsuda e os alelos HLA-DR2/HLA-DR3 e HLA-DQ1 relacionados com as formas clínicas da hanseníase em 176 pacientes (50 TT, 50 LL e 76 B). Os resultados obtidos não revelaram associação entre reação de Mitsuda e os alelos HLA nas formas clínicas isoladas; no entanto, quando analisados de acordo com a resposta ao teste de Mitsuda, associação significativa foi encontrada entre os pacientes Mitsuda negativos e HLA-DQ1 (p=0,002). Não foi observada associação entre reação de Mitsuda positiva e alelos HLA-DR2/DR3. Concluímos que existe importante participação do alelo HLA-DQ1 na ausência de resposta ao teste de Mitsuda. Sugerimos estudos mais específicos para este alelo.

In this study, we aimed to compare the Mitsuda skin test with the alleles HLA-DR2/HLA-DR3 and HLA-DQ1, in relation to the clinical forms of leprosy in 176 patients (50 TT, 50 LL and 76 B). The results obtained did not reveal any association between the Mitsuda reaction and the HLA alleles in the clinical forms isolated. However, when analyzed according to Mitsuda test response, a significant association was found between patients with negative Mitsuda reaction and HLA-DQ1 (p=0.002). No association was observed between positive Mitsuda reaction and the HLA-DR2/DR3 alleles. We concluded that the allele HLA-DQ1 has an important participation when there is no response to the Mitsuda test. We suggest that more specific studies should be developed on this allele.

Prevalence of HLA antibodies and its impact on graft function in a group of kidney transplant recipients: a cross-sectional study.

UNLABELLED: HLA alloantibodies (Abs) are associated with chronic rejection and poorer graft survival. The current study was designed to document the prevalence of HLA Abs in a group of kidney transplant recipients (KTR) and its impact on graft function. PATIENTS AND METHODS: 283 KTR transplanted between January 1990 and December 2003 who had a functional graft were invited to participate. 198 KTR were enrolled. HLA class I and II Abs were measured by Luminex-One Lambda. Graft function was assessed by DeltaCr and GFR calculated by the Levey formula. RESULTS: Median post-kidney transplant (post-KT) follow-up was 51.4 (4.3 to 176.3) months. Forty-four (22.2%) KTR were found to have class I and/or class II Abs. Eleven had both class I and II Abs, ten were positive only for class I, and 23 for class II. Overall, no significant difference was seen in renal function. The DeltaCr for Ab positive and Ab negative were -0.24+/-0.84 and -0.17+/-0.60 mg/dL (P=0.54), respectively. The GFR for Ab positive and Ab negative were 64.4+/-26 and 60.2+/-20 mL/min (P=0.25), respectively. No statistically significant difference was found between HLA Abs and number of HLA mismatches, gender, blood transfusions, pre-KT pregnancies, DGF, history of acute rejection, and chronic allograft nephropathy. Adjusting analysis by transplant year showed no significant difference. CONCLUSION: The prevalence of HLA antibodies was similar to previous reports. In this cross-sectional study, the presence of HLA antibodies was not related to a negative impact on renal function.

Anti-HLA class II antibodies and chronic allograft nephropathy.

The purpose of this study was to prospectively analyze the relationship between posttransplant IgG anti-HLA class I and/or class II antibodies and graft failure due to chronic allograft nephropathy (CAN). We studied 512 first kidney graft recipients transplanted at a single center, with a graft functioning for at least 3 years. A single blood sample was collected from each patient, and the presence of antibodies was evaluated by PRA-ELISA. The median post-transplant time after blood collection was 4.4 years and did not differ between patients with or without anti-HLA antibodies. Among the 512 recipients, 55 (10.7%)were positive for anti-HLA class II, 20 (3.9%) for anti-HLAclass I, and 16 (3.1%) for anti-HLA class I and class II antibodies. After antibody evaluation, the patients were followed for at least 34 months. Anti-HLA class II antibodies and serum creatinine levels > or = 2 mg/dl at the time of antibody testing were independently associated with graft loss due to CAN, with relative risks (RR) of 3.29 and 13.82, respectively. When both factors were present, the RR rose to 36.07. In graft biopsies with CAN, the lesions believed to be mediated by antibodies (chronic glomerulopathy, arteriosclerosis, and lamination of the peritubular capillaries basement membrane) were more prevalent in biopsies with CAN from patients with anti-HLA class II antibodies. In conclusion, our data support not only an association but also a pathogenic role of anti-HLA class II antibodies in approximately 40% of chronic allograft cases.

Clinical relevance of low levels of preformed alloantibodies detected by flow cytometry in the first year post-kidney transplantation.

OBJECTIVE: To determine the prevalence of transplants performed with a false-negative cytotoxicity cross-match and to analyze the clinical relevance of alloantibodies (Ab) detected only by flow cytometry (flow). METHODS: We studied 66 patients undergoing kidney transplantation from a cadaveric donor. All patients had a simultaneous negative T+AHG+DTT and B+DTT. Pretransplant sera were retrospectively analyzed by flow cytometry according to an Emory University protocol: (1) T+ and B-: Ab anti-class I; (2) T- and B+: anti-class II; (3) T+B+: anti-class I + II. Chi-square, Fisher exact, Student t test, and Kaplan Meier analyses were employed with significance assigned at P < or = .05. RESULTS: The overall incidence of false-negative cytotoxicity was 33.3% (22/66), namely, 6.1% (n = 4) anti-class I; 9.1% (n = 6) anti-class II; and 18.2% (n = 12) anti-class I + II. Primary nonfunctioning grafts occurred in 6.8% (3/44) and 13.6% (3/22) negative and positive flow patients (two anti-class I + II and one class II; P = .39). The incidence of graft loss in the first year was respectively, 13.6% (6/44) and 18.2% (4/22; two anti-class II and two anti-class I + II; P = .72). Compared to flow-negative grafts, creatinine levels were significantly higher among flow-positive patients at 8 and 12 weeks. One-year graft survivals were 86.4% among negative versus 81.8% for the positive group (P = .67). CONCLUSIONS: We observed that 33% of kidney transplant recipients had low levels of alloantibodies detected only by flow. This single factor was associated with the worst graft function in the first trimester with a suggestion of a higher risk for non-functioning graft.

Human leukocyte antigen class II control of the immune response to p126-derived amino terminal peptide from Plasmodium falciparum.

We investigated the relationships between class II human leukocyte antigens (HLA) and the antibody response to Plasmodium falciparum p126 protein and to its amino-terminal portion (Nt47) in 2 malaria-endemic villages in Brazil, Colina and Ribeirinha. All people from the endemic areas had anti-p126 antibodies, and the frequencies of anti-Nt47 antibodies were similar in both communities (66% for Colina and 75% for Ribeirinha). Typing of HLA showed that Colina and Ribeirinha groups had no significant differences in HLA antigen frequencies. However, in both groups, significant associations between positive response to anti-Nt47 and presence of HLA-DR4, as well as between absence of response and presence of HLA-DR15, were observed. The predominance of positive responses to Nt47 among HLA-DR4 people was independent of the presence of any particular allele. There was no evidence for association between HLA-DQB1 alleles and antibody response to Nt47. Thus, naturally exposed people with different HLA class II antigens seem to respond differently to Nt47, indicating that the choice of relevant peptide sequences may have important consequences for subunit vaccine development.

Paraneoplastic syndromes associated with anti-Hu antibodies.

Paraneoplastic syndromes are disorders associated with cancer but without a direct effect of the tumor mass or its metastases on the nervous system. Small cell carcinoma of lung associated with paraneoplastic sensory neuronopathy and/or paraneoplastic encephalomyelitis with the presence of anti-Hu antibodies has been termed "anti-Hu syndrome." Anti-Hu associated PSN-PEM is an immune disorder in which both cell-mediated and humoral mechanisms are involved. Patients are considered affected by Anti-Hu associated PSN-PEM when they develop clinical signs and symptoms of CNS dysfunction and/or sensory neuropathy not caused by metastases or other disorders, and serum or cerebrospinal fluid is positive for Hu abs. SCLC is found in more than 90% of patients with cancer and positive Hu abs. Individual patients with Hu abs associated to SCLC may suffer PSN-PEM, limbic encephalitis, brainstem encephalopathy, opsoclonus-myoclonus, paraneoplastic cerebellar degeneration or myelopathy. Hu abs have a specificity of 99% and sensitivity of 82% in detecting paraneoplastic neurological syndromes. There are two types of treatment: the first is to treat the cancer, the second is to suppress the immune reaction with the use of corticosteroids, cyclophosphamide, azathioprine, plasma exchange, intravenous immunoglobulin and immunoadsorption; however, treatment of paraneoplastic syndromes is generally unsatisfactory.

Human leukocyte antigen class II alleles in white Brazilian patients with celiac disease.

BACKGROUND: Celiac disease (CD) is a permanent gluten intolerance disorder characterized by malabsorption, intestinal mucosa villus atrophy, and crypt hyperplasia. Clinical and histologic features improve in persons consuming a gluten free diet. The pathogenesis of CD involves environmental, genetic, and immunologic factors. METHODS: The frequencies of human leukocyte antigen (HLA) class II alleles were evaluated in white Brazilian patients who had CD and compared with those observed in healthy individuals from the same geographical area (Ribeirão Preto, São Paulo) and of similar ethnic background. Twenty-five patients with CD, 11 females and 14 males, and 91 control individuals were studied. The HLA class II alleles were typed using amplified DNA hybridized with sequence-specific primers. Statistical analysis was performed using the two-tailed Fisher exact test. The relative risk (RR), etiologic fraction (EF), and preventive fraction (PF) were also estimated. The EF represents the attributable risk for the development of CD at the population level, whereas PF represents the protective risk. RESULTS: The frequency of the HLA-DRB1*03, HLA-DRB1*07, and HLA-DQB1*02 alleles was significantly increased in patients. The RR conferred by these alleles was 5.35, 7.15, and 10.6, respectively, and the EF was 48.7%, 44.7%, and 76%, respectively. The frequency of HLA-DQB1*06 alleles was significantly decreased in CD patients, conferring an RR of 0.08 and a PF of 48%. CONCLUSIONS: The results show that HLA-DRB1*03, HLA-DRB1*07, and HLA-DQB1*02 alleles conferred susceptibility to CD in Brazilian patients. In contrast, HLADQB1*06 alleles conferred protection against development of the disease.

H-2M molecules, like MHC class II molecules, are targeted to parasitophorous vacuoles of Leishmania-infected macrophages and internalized by amastigotes of L. amazonensis and L. mexicana.

In their amastigote stage, Leishmania are obligatory intracellular parasites of mammalian macrophages, residing and multiplying within phagolysosomal compartments called parasitophorous vacuoles (PV). These organelles have properties similar to those described for the MHC class II compartments of antigen-presenting cells, sites where peptide-class II molecule complexes are formed before their expression at the cell surface. After infection with Leishmania amazonensis or L. mexicana, endocytosis and degradation of class II molecules by intracellular amastigotes have also been described, suggesting that these parasites have evolved mechanisms to escape the potentially hazardous antigen-presentation process. To determine whether these events extend to other molecules of the antigen-presentation machinery, we have now studied the fate of the MHC molecule H-2M in mouse macrophages infected with Leishmania amastigotes. At least for certain class II alleles, H-2M is an essential cofactor, which catalyses the release of the invariant chain-derived CLIP peptide from the peptide-binding groove of class II molecules and facilitates the binding of antigenic peptides. H-2M was detected in PV of mouse macrophages infected with various Leishmania species including L. amazonensis, L. mexicana, L. major and L. donovani. PV thus contain all the molecules required for the formation of peptide-class II molecule complexes and especially of complexes with parasite peptides. The present data indicate, however, that if this process occurs, it does not lead to a clear increase of SDS-stable compact (alpha)(beta) dimers of class II. In PV that contained L. amazonensis or L. mexicana, both class II and H-2M molecules often colocalized at the level where amastigotes bind to the PV membrane, suggesting that these molecules are physically associated, directly or indirectly, and possibly interact with parasite components. Furthermore, as class II molecules, H-2M molecules were internalized by amastigotes of these Leishmania species and reached parasite compartments that also contained class II molecules. Immunostaining of H-2M within parasites was increased by treatment of infected macrophages with the cysteine protease inhibitors Z-Phe-AlaCHN2 or Z-Phe-PheCHN2 or by incubation of the parasites with the same inhibitors before infection. These data thus support the idea that amastigotes of certain Leishmania species capture and degrade some of the molecules required for antigen presentation. To examine whether endocytosis of class II molecules by the parasites occurs through interactions with parasite components involving their peptide-binding groove, we made use of the fact that a large fraction of the class II molecules of H-2M(alpha) knock-out H-2(b) mice are occupied by the peptide CLIP and are unable to bind other peptides. We found that, in Leishmania-infected macrophages of these mutant mice, class II-CLIP complexes reached PV and were internalized by amastigotes. These results thus prove that endocytosis of class II molecules by amastigotes (1) is H-2M-independent and (2) does not necessarily involve the peptide-binding pocket of these molecules. Altogether, these data are compatible with an endocytic mechanism based on general properties shared by classical and non-classical class II molecules.

Ultrastructural localization of anionic sites and lectin-binding sites in sarcoid human alveolar macrophages during interaction with T-lymphocytes.

Sarcoidosis alveolitis is caused by an unknown stimulus activating alveolar macrophages (AM) and T-lymphocytes. During antigen presentation, the complex HLA class II molecule/processed peptide, on the surface of sarcoid AM, induces the T-lymphocyte to proliferate. Altered glycosylation patterns of cell surface glycoproteins such as class II molecules in inflammatory states, may enhance the antigen-presenting capability of AM. In order to know if anionic sites and lectin-binding sites take part in the process of antigen presentation by alveolar macrophages, cells obtained from bronchoalveolar lavage of patients with pulmonary sarcoidosis were incubated with cationized ferritin (CF) and colloidal gold complexed lectins (BSL-I-A4; RCA-I; RCA-II; WGA) for 30 min at 4 degrees C. After incubation, the cells were fixed with 4% paraformaldehyde, 2% glutaraldehyde, postfixed, and Epon embedded. The CF particles were uniformly distributed over the entire cell surface of the lymphocyte, and formed clusters on the surface of the macrophage mainly at the adhesion region between the AM and the lymphocytes. We found enhanced binding of BSL-I-A4 by AM, while WGA and RCA were poorly taken up by these cells. Gold-BSL-I-A4 was distributed randomly on the plasma membrane of the AM, and clustered in the adhesion region with lymphocytes. These results suggest that anionic sites and alpha-D-N-acetyl-galactosamine residues labeled with gold-BSL-I-A4 may be involved in the process of antigen presentation by sarcoid alveolar macrophages.

Influence of the HLA class II polymorphism in chronic Chagas' disease.

Chagas' disease or American trypanosomiasis due to Trypanosoma cruzi has existed at least since the time of the Inca empire and contributes significantly to cardiovascular morbidity and mortality in several countries of this continent. Due to the fundamental role of human class II molecules polymorphic residues in the control of the immune response, a study was designed to define by DNA typing HLA class II alleles in a sample of 67 serologically positive individuals with and without cardiomyopathy and in 156 healthy controls of similar ethnic origin. Genomic DNA extraction, PCR amplification of the HLA-DRB1 and DQB1 second exon regions and hybridization to labelled specific probes were carried out following the 11th International Histocompatibility Workshop reference protocol. Comparison of DRB1 and DQB1 allele frequencies among the patients and control subjects showed a decreased frequency of DRB1*14 and DQB1*0303 in the patients, suggesting independent protective effects to the chronic infection in this population. Allele frequencies comparison between patients with and without cardiomyopathy showed a higher frequency of DRB1*01, DRB1*08 and DQB1*0501 and a decreased frequency of DRB1*1501 in the patients with arrhythmia and congestive heart failure. The results suggest that HLA Class II genes may be associated with the development of a chronic infection and with heart damage in Chagas' disease.

[Superantigens in human disease]. / Superantígenos en la enfermedad humana.

Superantigens include viral and bacterial products, mainly of streptococci, staphylococci that stimulate T cells to proliferate nonspecifically through interaction with class II major histocompatibility complex products on antigen-presenting cells and then with variable regions on the beta chain of T cell receptor complex. Superantigens cause symptoms via release of immune cytokines. These proteins should be considered potential cause of illnesses such as rheumatic fever, arthritis. Kawasaki syndrome, atopic dermatitis, and guttate psoriasis because of their potent immune system-altering capacity.