It is widely thought that expression of ABH antigens on platelets is insufficient to materially affect the survival of ABH-incompatible platelets in transfusion recipients, but anecdotal reports of poor survival of A and B mismatched platelets suggest that this is not always the case. The A and B antigen expression on platelets of 100 group A1 and group B blood donors was measured, and 7% and 4%, respectively, had platelets whose A and B antigen levels consistently exceeded the mean plus 2 SD. On the basis of flow cytometric and statistical analysis, donors whose platelets contained higher than normal levels of A antigen were subdivided into 2 groups, designated Type I and Type II (“high expressers”). Serum A1- and B-glycosyltransferase levels of A and B high expressers were significantly higher than those of group A1 and B individuals with normal expression. H antigen levels were low on the red cells of high expressers, indicating that the anomaly affects other cell lineages. Immunochemical studies demonstrated high levels of A antigen on various glycoproteins (GPs) from high-expresser platelets, especially GPIIb and PECAM (CD31). The A1 Type II high-expresser phenotype was inherited as an autosomal dominant trait in one family. The sequences of exons 5, 6, and 7 of the A1-transferase gene of one Type II A1 high expresser and exon 7 from 3 other genes were identical to the reported normal sequences. Further studies are needed to define the molecular basis for the high-expresser trait and to characterize its clinical implications.

It is widely thought that expression of ABH antigens on platelets is insufficient to materially affect the survival of ABH-incompatible platelets in transfusion recipients, but anecdotal reports of poor survival of A and B mismatched platelets suggest that this is not always the case. The A and B antigen expression on platelets of 100 group A1 and group B blood donors was measured, and 7% and 4%, respectively, had platelets whose A and B antigen levels consistently exceeded the mean plus 2 SD. On the basis of flow cytometric and statistical analysis, donors whose platelets contained higher than normal levels of A antigen were subdivided into 2 groups, designated Type I and Type II (“high expressers”). Serum A1- and B-glycosyltransferase levels of A and B high expressers were significantly higher than those of group A1 and B individuals with normal expression. H antigen levels were low on the red cells of high expressers, indicating that the anomaly affects other cell lineages. Immunochemical studies demonstrated high levels of A antigen on various glycoproteins (GPs) from high-expresser platelets, especially GPIIb and PECAM (CD31). The A1 Type II high-expresser phenotype was inherited as an autosomal dominant trait in one family. The sequences of exons 5, 6, and 7 of the A1-transferase gene of one Type II A1 high expresser and exon 7 from 3 other genes were identical to the reported normal sequences. Further studies are needed to define the molecular basis for the high-expresser trait and to characterize its clinical implications.

Establishing a level of comfort in which students feel at ease in an online course is primarily the responsibility of the professor, but fostering this community of inquiry is a complicated task. While research is rich with regard to broad instructional practices that can be used to foster social presence, practical strategies and examples for faculty to use are lacking in the literature. This chapter describes specific social presence-related instructional strategies used to foster an atmosphere of sharing, support, and success for students enrolled in online courses.