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N El-Awar

Publications and source records attributed to N El-Awar.

5 recordsLinked to original sources
PubMed2006

Development of nondonor-specific HLA-DR antibodies in allograft recipients is associated with shared epitopes with mismatched donor DR antigens.

Our previous studies showed that not only donor-specific antibodies (DSA) but also nondonor-specific antibodies (NDSA) were detected in the peripheral blood of allograft recipients. The molecular mechanism involved in the development of NDSA is examined here. HLA class II single antigen (SA) beads were used to determine the presence of HLA DR-specific antibodies in renal transplant recipients with failed allografts. Sequence-based antibody-epitope mapping was determined by the comparison of the reaction profiles of different SA recombinant cell lines containing unique epitope pattern. We found that 22 out of 65 recipients with failed grafts developed antibodies against donor HLA DR that is a mismatch with the recipient. Three of them had only DSA while 19 patients had not only DSA but also NDSA. An average of 77.3% of NDSA reacted with targets that share amino acid sequence with mismatched donor DR antigens. Either surface or nonsurface amino acid residues may constitute an antibody epitope. In conclusion, development of NDSA in allograft recipients may be associated with shared amino acids with mismatched donor antigens. SA beads technique not only helps to determine antibody specificities but also provides an ideal approach for the identification of potential HLA antibody epitopes.

Epitopes↗
PubMed2005

HLA antibody identification with single antigen beads compared to conventional methods.

Single antigen (SA) beads coated with Class I HLA antigens from recombinant cells lines were tested with 170 mouse monoclonal antibodies (mAbs). The HLA specificities of all mAbs were previously determined by the cytotoxicity assay (CDC). There were 100 mAbs which produced the expected reactions with the SA beads, indicating that the SA beads coated with the antigens had reacted properly. Sixty one mAbs were positive with one or more antigen(s) that shared unique amino acids (aa) possibly constituting a common epitope. Single antigen beads were then tested on 58 alloantisera analyzed by 63 laboratories of the UCLA serum exchange (UCLA-SE). Many specificities detected by the single antigen beads were missed by the laboratories employing conventional methods. Most of the missed specificities were of lower frequency, although in some instances, even common specificities were missed. These findings have important implications regarding the use of specificities to predict positive crossmatch, to selecting platelet donors for highly sensitized recipients, and analysis of sera for donor specific antibodies.

Animals↗
PubMed1981

Cytotoxic monoclonal antibody to a human leiomyosacoma.

A monoclonal antibody produced by the hybridoma technique against a human leiomyosarcoma was highly cytotoxic in dilutions of 1:64 000 to the original tumour cells. The antibody was unreactive with most normal cells (lymphocytes, 120 donors; spleen cells, 73/75; monocytes, 16; granulocytes, 25; platelets, 12; red cells, 11) and could not be absorbed out by smooth muscle from the small intestine or by spleen cells. Its specificity for the tumour was high since it did not react with cells from 40 patients with leukaemia, from 8 patients with other tumours, and from 7 cultured tumour lines. The only other cell that it reacted with (at 1:4000 dilution) was line 8402, a T acute lymphocytic leukaemia line. This monoclonal antibody may be suitable for therapeutic trials.

Antibodies, Neoplasm↗
PubMed1980

Discrimination of T, B, and null lymphocytes by electronic sizing.

T, B, and null lymphocytes isolated by sheep red blood cells (SRBC) rosetting or adherence to a nylon wool column had distinct size differences according to Coulter counter size analysis. The diameters in microns were as follows: B = 6.42, T = 6.76, null = 7.16, granulocytes = 8.42, and monocytes = 9.02. Coulter size distributions of cell preparations were compared to the proportions of cells with E, EAC, and surface immunoglobulin (SIg) markers in these preparations as well as their reactivity to HLA--DR antisera and rabbit anti-B-lymphocyte antisera. Cell preparations monitored by Coulter sizing produced the expected results in mixed lymphocyte culture (MLC) testing. That is, T cells responded but did not stimulate whereas B lymphocytes and monocytes stimulated but did not respond. NULL lymphocytes both stimulated and responded. In antibody-dependent cell-mediated cytotoxicity (ADCC), null lymphocytes and monocytes functioned as effectors, whereas T lymphocytes and granulocytes did not. B lymphocyte preparations were intermediate in activity. Coulter sizing is a rapid, simple means of assessing the purity of suspensions enriched for T, B, and null lymphocytes.

Animals↗