Evidence for a mechanosensitive calcium influx into red cells.

Red cells exposed to glycophorin A reactive antibodies and lectins develop a non-specific cation permeability. To determine if this might be due to the activation of a non-selective mechanosensitive channel we have subjected red cells, loaded with a calcium responsive fluorescent probe, to filtration through 5 and 3 microm pores. Calcium entered 28% of normal red cells at the moment of deformation when 3 microm filtered, a finding consistent with the transient activation of a mechanosensitive channel.

Clinical manifestations associated with the aberrant expression of the soluble granulocyte-macrophage colony-stimulating factor receptor in patients presenting with haematological malignancies.

The receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) can exist as both transmembrane (tmGMRalpha) and soluble (solGMRalpha) isoforms, and the latter, is a normal constituent of human plasma. We investigated if aberrant solGMRalpha expression occurs in haematopoietic malignancies and whether or not solGMRalpha expression levels correlated with clinical presentation. Compared with the normal population, patients with acute lymphoblastic leukaemia (ALL) had low levels of solGMRalpha whereas clonal disorders of the myeloid lineage demonstrated higher levels of solGMRalpha.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and inflammatory stimuli up-regulate secretion of the soluble GM-CSF receptor in human monocytes: evidence for ectodomain shedding of the cell surface GM-CSF receptor alpha subunit.

Soluble GM-CSF receptor alpha subunit (sGMRalpha) is a soluble isoform of the GMRalpha that is believed to arise exclusively through alternative splicing of the GMRalpha gene product. The sGMRalpha mRNA is expressed in a variety of tissues, but it is not clear which cells are capable of secreting the protein. We show here that normal human monocytes, but not lymphocytes, constitutively secrete sGMRalpha.

Glycophorin A-mediated haemolysis of normal human erythrocytes: evidence for antigen aggregation in the pathogenesis of immune haemolysis.

The inexplicable severity of anti-Pr autoimmune haemolytic anaemia led us to test the hypothesis that the haemolysis was primarily due to a change in the function of glycophorin A, on which the Pr antigen is located. The lectins Maclura pomifera and wheat germ agglutinin that bind to glycophorin A induced the haemolysis of normal erythrocytes in vitro. Lectin binding led to an increase in erythrocyte membrane permeability to sodium and potassium, the former resulting in an influx of water and subsequent haemolysis.