Helicobacter pylori is associated with development of gastritis, gastric ulcers, and adenocarcinomas in humans. The Lewis ^b (Le ^b ) blood group antigen mediates H. pylori attachment to human gastric mucosa. Soluble glycoproteins presenting the Le ^b antigen or antibodies to the Le ^b antigen inhibited bacterial binding. Gastric tissue lacking Le ^b expression did not bind H. pylori . Bacteria did not bind to Le ^b antigen substituted with a terminal GalNAcα1-3 residue (blood group A determinant), suggesting that the availability of H. pylori receptors might be reduced in individuals of blood group A and B phenotypes, as compared with blood group O individuals.

bcl-x is a member of the bcl-2 gene family, which may regulate programmed cell death. Mice were generated that lacked Bcl-x. The Bcl-x-deficient mice died around embryonic day 13. Extensive apoptotic cell death was evident in postmitotic immature neurons of the developing brain, spinal cord, and dorsal root ganglia. Hematopoietic cells in the liver were also apoptotic. Analyses of bcl-x double-knockout chimeric mice showed that the maturation of Bcl-x-deficient lymphocytes was diminished. The life-span of immature lymphocytes, but not mature lymphocytes, was shortened. Thus, Bcl-x functions to support the viability of immature cells during the development of the nervous and hematopoietic systems.

The cytosolic protein APAF1, human homolog of C. elegans CED-4, participates in the CASPASE 9 (CASP9)-dependent activation of CASP3 in the general apoptotic pathway. We have generated by gene trap a null allele of the murine Apaf1. Homozygous mutants die at embryonic day 16.5. Their phenotype includes severe craniofacial malformations, brain overgrowth, persistence of the interdigital webs, and dramatic alterations of the lens and retina. Homozygous embryonic fibroblasts exhibit reduced response to various apoptotic stimuli. In situ immunodetection shows that the absence of Apaf1 protein prevents the activation of Casp3 in vivo. In agreement with the reported function of CED-4 in C. elegans, this phenotype can be correlated with a defect of apoptosis. Our findings suggest that Apaf1 is essential for Casp3 activation in embryonic brain and is a key regulator of developmental programmed cell death in mammals.

The proapoptotic protein BAX contains a single predicted transmembrane domain at its COOH terminus. In unstimulated cells, BAX is located in the cytosol and in peripheral association with intracellular membranes including mitochondria, but inserts into mitochondrial membranes after a death signal. This failure to insert into mitochondrial membrane in the absence of a death signal correlates with repression of the transmembrane signal-anchor function of BAX by the NH₂-terminal domain. Targeting can be instated by deleting the domain or by replacing the BAX transmembrane segment with that of BCL-2. In stimulated cells, the contribution of the NH₂ terminus of BAX correlates with further exposure of this domain after membrane insertion of the protein. The peptidyl caspase inhibitor zVAD-fmk partly blocks the stimulated mitochondrial membrane insertion of BAX in vivo, which is consistent with the ability of apoptotic cell extracts to support mitochondrial targeting of BAX in vitro, dependent on activation of caspase(s). Taken together, our results suggest that regulated targeting of BAX to mitochondria in response to a death signal is mediated by discrete domains within the BAX polypeptide. The contribution of one or more caspases may reflect an initiation and/or amplification of this regulated targeting.