Biomedical subjects

Stephen M Hedrick

Publications and source records attributed to Stephen M Hedrick.

21 records · Page 2Linked to original sources

PubMed2002

T cell development: bottoms-up.

An important but laborious approach to understanding the concepts underlying T cell lineage commitment is to characterize the cis-acting control elements governing the expression of CD4 and CD8. Previous studies on the CD4 gene have shown that lineage commitment information is directed by the intronic silencer; however, a similarly simple mechanism for controlling CD8 gene expression has not been uncovered. In this issue of Immunity, two groups have investigated the role of putative enhancers in the CD8 locus. The deletion of three different elements in the intergeneic region between CD8 beta and CD8 alpha provides evidence for control at the level of chromatin accessibility.

Animals↗

PubMed2002

A mouse strain defective for alphabeta versus gammadelta T cell lineage commitment.

As a result of a transgene insertion and chromosomal deletion, a mutant mouse strain has been found that is defective in the lineage commitment step that produces a balance of alphabeta and gammadelta T cells. The mice produce a reduced population of alphabeta CD4 T cells and almost no alphabeta CD8 T cells. Within the CD4 and CD8 populations in the thymus there exist abnormal subsets that express the gammadelta TCR. These gammadelta TCR-expressing cells populate the peripheral lymphoid organs such that up to 75% of the CD8 T cells in the lymph nodes and spleen express a gammadelta TCR. Further analyses indicate that the regulation that prevents dual TCR expression has been impaired. The locus of insertion and deletion was mapped to chromosome 10 26 cM. We have analyzed the entire locus and, in addition, the gene expression changes in early thymocytes were analyzed by gene array technology. The analysis of this mutant strain indicates that the alphabeta versus gammadelta lineage decision can be profoundly disregulated independently of successful gene rearrangements.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Generation of mice deficient for macrophage galactose- and N-acetylgalactosamine-specific lectin: limited role in lymphoid and erythroid homeostasis and evidence for multiple lectins.

Macrophage receptors function in pattern recognition for the induction of innate immunity, in cellular communication to mediate the regulation of adaptive immune responses, and in the clearance of some glycosylated cells or glycoproteins from the circulation. They also function in homeostasis by initiating the engulfment of apoptotic cells. Evidence has suggested that macrophage receptors function to recognize cells that are destined for programmed cell death but not yet overtly apoptotic. We have examined the function of a macrophage receptor specific for unsialylated glycoproteins, known as the mouse macrophage galactose- and N-acetylgalactosamine-specific lectin (mMGL) (Ii et al., J. Biol. Chem. 265:11295-11298, 1990; Sato et al., J. Biochem. [Tokyo] 111:331-336, 1992; Yamamoto et al., Biochemistry 33:8159-8166, 1994). With targeted disruption, we tested whether mMGL is necessary for macrophage function, controlled thymic development, the loss of activated CD8 T cells, and the turnover of red blood cells. Evidence indicates that mMGL may play a nonessential role in several of these macrophage functions. Experiments are presented that indicate the existence of another galactose- and N-acetylgalactosamine-recognizing lectin distinct from mMGL. This may explain the absence of a strong phenotype in mMGL-deficient mice.

Animals↗