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Biomedical subjects

Z Kurepa

Publications and source records attributed to Z Kurepa.

6 recordsLinked to original sources
PubMed2000

Comparative ability of Qdm/Qa-1b, kb, and Db to protect class Ilow cells from NK-mediated lysis in vivo.

The class Ib molecule Qa-1(b) binds the class Ia leader peptide, Qdm, which reacts with CD94/NKG2R on NK cells. We have generated a gene that encodes the Qdm peptide covalently attached to ss(2)-microglobulin (ss(2)M) by a flexible linker (Qa-1 determinant modifier (Qdm)-ss(2)M). When this construct is expressed in TAP-2(-) or ss(2)M(-) cells, it allows for the expression of a Qdm-ss(2)M protein that associates with Qa-1(b) to generate the Qdm epitope, as detected by Qdm/Qa-1(b)-specific CTL. To test the biological significance of expression of this engineered molecule, we injected TAP-2(-) RMAS-Qdm-ss(2)M cells into C57BL/6 mice and measured their NK cell-mediated clearance from the lungs at 2 h. RMAS cells transfected with Qdm-ss(2)M were resistant to lung clearance, similar to RMA cells or RMAS cells in anti-asialo-GM(1)-treated mice, while untransfected or ss(2)M-transfected RMAS cells were rapidly cleared. Further, pulsing RMAS cells with either Qdm, a K(b)-, or D(b)-binding peptide showed equivalent protection from clearance, indicating that a single class Ia or Ib molecule can afford complete protection from NK cells in this system. In contrast, injection of RMAS cells into DBA/2 animals, which express low levels of receptors for Qdm/Qa-1(b), resulted in protection from lung clearance if pulsed with a K(b)- or D(b)-binding peptide, but not the Qa-1(b)-binding peptide, Qdm.

Animals↗
PubMed1999

Cutting edge: expression of functional CD94/NKG2A inhibitory receptors on fetal NK1.1+Ly-49- cells: a possible mechanism of tolerance during NK cell development.

Fetal liver- and thymus-derived NK1.1+ cells do not express known Ly-49 receptors. Despite the absence of Ly-49 inhibitory receptors, fetal and neonatal NK1.1+Ly-49- cells can distinguish between class Ihigh and class Ilow target cells, suggesting the existence of other class I-specific inhibitory receptors. We demonstrate that fetal NK1. 1+Ly-49- cell lysates contain CD94 protein and that a significant proportion of fetal NK cells are bound by Qa1b tetramers. Fetal and adult NK cells efficiently lyse lymphoblasts from Kb-/-Db-/- mice. Qa1b-specific peptides Qdm and HLA-CW4 leader peptide specifically inhibited the lysis of these blasts by adult and fetal NK cells. Qdm peptide also inhibited the lysis of Qa1b-transfected human 721.221 cells by fetal NK cells. Taken together, these results suggest that the CD94/NKG2A receptor complex is the major known inhibitory receptor for class I (Qa1b) molecules on developing fetal NK cells.

Aging↗
PubMed1998

Qa-1b binds conserved class I leader peptides derived from several mammalian species.

Qa-1b binds a peptide (AMAPRTLLL), referred to as Qdm (for Qa-1 determinant modifier), derived from the signal sequence of murine class Ia molecules. This peptide binds with high affinity and accounts for almost all of the peptides associated with this molecule. Human histocompatibility leukocyte antigen (HLA)-E, a homologue of Qa-1b, binds similar peptides derived from human class Ia molecules and interacts with CD94/NKG2 receptors on natural killer cells. We used surface plasmon resonance to determine the ability of Qa-1b to bind related ligands representing peptides derived from the leaders of class I molecules from several mammalian species. All of the peptides reported to bind HLA-E bound readily to Qa-1b. In addition, peptides derived from leader segments of different mammals also bound to Qa-1b, indicating a conservation of this "Qdm-like" epitope throughout mammalian evolution. We have attempted to define a minimal peptide on a polyglycine backbone that binds Qa-1b. Our previous findings showed that P2 and P9 are important but not sufficient for binding to Qa-1b. Although a minimum peptide (GMGGGGLLL) bound Qa-1(b), its interaction was relatively weak, as were peptides sharing five or six residues with Qdm, indicating that multiple native residues are required for a strong interaction. This finding is consistent with the observation that this molecule preferentially binds this single ligand.

Amino Acid Sequence↗
PubMed1997

Peptide binding to the class Ib molecule, Qa-1b.

We have analyzed the interaction of a nonameric peptide (Qdm) derived from the leader sequence of a MHC D region molecule with the class Ib molecule, Qa-1b. Using a direct binding assay with radiolabeled peptide on intact cells, we show specific binding of iodinated Qdm peptide to Qa-1b expressing cells. Specificity was confirmed by experiments in which the binding of iodinated peptide was blocked by unlabeled Qdm and not by control peptides. This allowed us to determine the on- and off-rate of peptide binding to Qa-1b, its binding affinity, and number of available peptide-binding sites per cell. Optimal binding occurs at 4 degrees C, and most of the binding to Qa-1b occurs within the first 10 min and peaks after 3 h. The dissociation of the peptide from cells has a t1/2 of approximately 10 h. The Kd is calculated between 0.2 and 1.1 x 10(-10) M, which is in the range or slightly higher than the Kd we measured for pMCMV to Ld (0.9 x 10(-10) M). The relatively high affinity of binding of the Qdm peptide and low dissociation rate could partially explain why a large portion of Qa-1b molecules are occupied with this single peptide species. We also changed each peptide residue to Ala or Gly to determine its effect on binding. Substitution of Leu at position 9 to Ala strongly reduced peptide binding, while changes at positions 2 (Met-->Ala) and 5 (Arg-->Ala) had a lesser effect. Binding to Qa-1b was completely abrogated with simultaneous Ala mutations at positions 2 and 9.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Influence of circadian light-dark alternations on macrophages and lymphocytes of CBA mouse.

The influence of circadian 12 h light-12 h dark alternations on CBA mouse macrophages and lymphocytes was determined using tests for macrophage spreading and ingestion ability or flow cytometry immunophenotyping of blood, lymph node, and spleen lymphocytes. The animals were tested every 4 h around the clock. Collected macrophages were incubated in vitro for 3 or 18 h. Monoclonal antibodies permitted detection of T-lymphocytes, suppressor-cytotoxic T-lymphocytes, helper-inducer T-lymphocytes, or B-lymphocytes. Two types of analyses were performed: First, the difference between the same intervals of the 12 h light or dark period was determined. The macrophage ingestion was significantly lower at the beginning and higher at the end of the dark period. We have also found a significant increase in blood T-lymphocytes of helper-inducer T-lymphocyte percentages and of the T helper-inducer: T suppressor-cytotoxic ratio during the dark period. Second, the ultradian variation during the 12 h light or dark period was determined. The variability was significant both for macrophage spreading and ingestion. Multiple significant variations of lymph node, spleen, or blood lymphocyte percentages were also observed. All of these data indicate that daily alteration of the lighting regimen significantly influences mouse peritoneal macrophage functions and various lymphocyte subsets.

Animals↗