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H A Araujo

Publications and source records attributed to H A Araujo.

7 recordsLinked to original sources
PubMed1998

Multiple epitopes of HLA-DRB1*0411 are recognized by T-cell clones originated from individuals carrying other DR4 subtypes.

HLA polymorphism dictates the binding and recognition of specific peptides, leading to variations in individual immune responses and may contribute to autoimmune disorders and outcome in organ transplantation. We have studied the molecular basis for the cellular recognition of DRB1*0411 in individuals carrying other sequence-related DR4-alleles by characterization of T-cell clones (TLC). A set of 166 TLC were raised by priming cells from DRB1*0401,0402 and DRB1*0405,0901 individuals and 52 of them recognized DRB1*0411. Five distinct patterns of T-cell allorecognition were found: DRB1*0411 alone, DRB1*0411 and 0405, DRB1*0411 and 0406, DRB1*0411 and 0407 and DRB1*0411, 0406 and 0407, depending on responder phenotypes and epitopes recognized by their T cells. A stretch of 30 amino acids on DRB1*0411 from positions 57 to 86 behaves as a functional domain and residues S57, R71, E74 and V86 seem to be crucial in forming immunogenic determinants recognized by these TLC. The knowledge of shared amino acid residues between closely related DR4 alleles, which show similar patterns of recognition by T cells could also be useful in the selection of prospective donors for clinical transplantation of solid organs or bone marrow.

Antibodies, Monoclonal↗
PubMed1995

Microvariation creates significant functional differences in the DR3 molecules.

Two DR3 molecules differ by four amino acids whose side chains point into the DR antigen-binding groove. To begin to assess the role of microvariation on DR3 function, DRB1*0302 residues were replaced with DRB1*0301 residues at beta-chain positions 26, 47, 86, and 47 plus 86. Murine fibroblast cell lines expressing DR(alpha, beta 1*0301), DR(alpha, beta 1*0302), and the four mutant 0302 molecules were examined for alloproliferative DR(alpha, beta 1*0302)-specific TLC stimulation and peptide binding. Changing position 26 had the most profound effect on T-cell recognition (seven of nine TLCs did not respond). Two TLCs did not respond to the mutant 0302V86 molecule and four TLCs that did respond to this mutant lost responsiveness when positions 47 and 86 were mutated together. These data suggest that each of these variant residues, including position 47, influence T-cell recognition. Surprisingly, none of the mutations had an effect on the absolute binding of HA 307-319 (DR[alpha, beta 1*0302] specific) and HSP 3-13 (DR[alpha, beta 1*0301] specific); however, the mutant 0302 molecules changed at position 86 (glycine to valine) consistently bound HA 307-319 at significantly higher levels than DR(alpha, beta 1*0302). These data for position 86 are in contrast to other DR molecules and indicate that peptide contact residues for a specific DR molecule cannot be predicted based on binding results obtained with other DR molecules. These data suggest that each of these variant groove residues, although not accessible to the TCR, contribute to the significant functional differences between the DR3 microvariants through subtle influences on the DR3-peptide complex.

Amino Acid Sequence↗
PubMed1989

[Lymphocyte imbalance in autoimmunity].

A subset of normal peripheral B lymphocytes expresses a T surface antigen recognized by monoclonal CD5. They form rosettes with mouse erythrocytes (MRBC). Other studies suggest that these B cells may have regulatory and helper properties. An expanded subset of lymphocytes forming MRBC was demonstrated in the peripheral blood of 31 Systemic Lupus Erythematosus (SLE) patients (14.4 +/- 2.8%) compared with normal controls (4.3 +/- 1.4%) and patients with tuberculosis (6.4 +/- 1.7%). Increased MRBC values correlated with disease severity. Investigation of cell surface antigen expression was attempted with enriched sedimented fractions using several monoclonal antibodies and immunofluorescent staining. Complete inhibition of MRBC formation was obtained with monoclonal antibodies against CD5, CD3 and CD8 while partial inhibition was observed with anti-Ia and no activity with CD4 and CD10 antibodies. Indirect evidence supports the concept that antilymphocyte antibodies cause T and B cell depletion and dysfunction. Sera from 12 patients with SLE and 28 with leprosy (LL) were analyzed for antibodies to lymphocytes in the microcytotoxicity assay: 87% of SLE and 57% of LL were positive. Lymphocytotoxic activity towards each cell type of a panel with 98 different HLA antigens was essentially the same and most sera were not specific for either T or B cells. Lymphocytotoxic sera from SLE and LL contained antibodies which inhibited MRBC formation.

Antibodies, Monoclonal↗
PubMed1985

HLA antigens and other genetic markers in the Mapuche Indians of Argentina.

A total of 107 Mapuche Indians living in western Argentina were studied with respect to 16 genetic systems. For HLA, there were a few differences in relation to previous studies; and considering the averages observed in 15 other South American tribes, Mapuche Indians showed low values for A2, A9 and C3, but high ones for A28 and B16. This is the first report of the presence (in low frequencies, 1-6%) of alleles C2, C6 and C7, as well as of DR antigens (most frequent alleles DR4 and DR2) in South American Indians. Some peculiar reactions shown by products of locus B suggest the presence of antigens that are characteristic of the Mapuche. As for the other systems, the frequencies of R1 (Rh) and PGM1(1) were lower but those for r (Rh), GLO1 and Hp1 were higher than the averages obtained considering previous studies of this ethnic group. Other salient findings were the variability observed in the PGM2 and C3 systems, and the low prevalence of Bfs.

Argentina↗