Several studies reported during the past year, most of which exploited novel in vivo positive selection systems, have addressed the basis of peptide involvement in positive selection of T cells. The very flexible, yet specific, requirements the studies demonstrate differ somewhat from the very specific requirements reported in earlier experiments relying on in vitro selection systems.

H ow has language developed in humans and what genetic changes underlie our unique cognitive abilities? Accounts of positive selection that lead to such abilities in humans fascinate us because of the insight they provide into our own evolution, and into the many genetic differences that distinguish us from other apes. The genes that became fi xed in our lineage as a result of positive selectio...

Ligand-independent signals that are produced by the B-cell antigen receptor (BCR) confer an important positive selection checkpoint for immature B cells. Generation of inappropriate signals imposes developmental arrest of immature B cells, though the fate of these cells has not been investigated. Studies have shown that the lack of CD19 results in inappropriate signaling. In immunoglobulin tran...

We exploited the natural histidine auxotrophy of Francisella species to develop hisD (encodes histidinol dehydrogenase) as a positive selection marker. A shuttle plasmid (pBR103) carrying Escherichia coli hisD and designed for cloning of PCR fragments replicated in both attenuated and highly virulent Francisella strains. During this work, we formulated a simplified defined growth medium for Fra...

In this report, we describe several approaches to improve the scalability and throughput of major genetic crosses in ends-out gene targeting. We generated new sets of targeting vectors and fly stocks and introduced a novel negative selection marker that drastically reduced the frequency of false-positive targeting candidates.

Transformation-associated recombination (TAR) is a cloning technique that allows specific chromosomal regions or genes to be isolated directly from genomic DNA without prior construction of a genomic library. This technique involves homologous recombination during spheroplast transformation between genomic DNA and a TAR vector that has 5' and 3' gene targeting sequences (hooks). Typically, TAR ...

a genetic marker is a gene or dna sequence with known localization on a chromosome. it can be de-scribed as a variation that can be measured or detected by a suitable method, and can be used subsequently to detect the presence of a specific genotype. such variations occurring at chromosomal or dna level can serve as genetic markers. the progress in development of molecular markers suggests thei...

Ligand-independent signals that are produced by the B-cell antigen receptor (BCR) confer an important positive selection checkpoint for immature B cells. Generation of inappropriate signals imposes developmental arrest of immature B cells, though the fate of these cells has not been investigated. Studies have shown that the lack of CD19 results in inappropriate signaling. In immunoglobulin tran...

Background: The immunomagnetic separation technique is the basis of monocyte isolation and further generation of monocyte-derived dendritic cells. Objective: To compare the efficiency of monocyte positive and negative separation, concentration of beads, and their impact on generated dendritic cells. Methods: Monocytes were obtained using monoclonal antibody-coated magnetic beads followed the Fi...