Haptoglobin gene subtyping by restriction enzyme analysis.

cell membrane (PS exposure detected by Annexin V binding) events. This is the first time that fetal NRBCs in the maternal circulation have been examined for PS exposure. Our analysis also differs from a recent report made by Kolialexi et al. (13), who reported a high percentage of Annexin V-positive fetal cells in the maternal circulation, which were proposed to be of an apoptotic nature. A major technical difference between this study and most other studies examining PS exposure is that these authors used an anti-Annexin V antibody for their analysis and not Ca 2ϩ-dependent Annexin V binding to exposed PS, as is the commonly used and well-validated approach. In this regard, it is likely that the use of this antibody can lead to the detection of endogenous Annexin V expression. This is important when considering trophoblast cells, where it is well established that Annexin V is found both in the cell cytoplasm (in undifferentiated cells) and on the cell surface (in differentiated cells) (14, 15). Consequently , it is possible that the use of this anti-Annexin V antibody may have detected nonapoptotic trophoblast cells. This issue may need to be resolved by determining the cellular origin of the fetal cells examined and whether similar results can be obtained by use of Annexin V-/PS-binding-based enrichment systems of the sort we used in this study. Although our study suggests that trafficking NRBCs do not undergo apoptosis on entry into the maternal circulation , the fate of other trafficking fetal cells, such as lymphocytes, or various progenitor cells is unclear. These studies will, however, be technically extremely challenging because of the scarcity of these fetal cell subpopula-tions. Fate of fetal nucleated erythrocytes circulating in maternal blood: apoptosis is induced by maternal oxygen concentration [Technical Brief]. Microchimerism of presumed fetal origin in thyroid specimens from women: a case-control study. Antiphosphatidylserine antibody removes annexin-V and facilitates the binding of prothrombin at the surface of a choriocarci-noma model of trophoblast differentiation. Haptoglobin is an acute-phase protein synthesized by the liver in response to inflammatory cytokines (1, 2). Its major function is to form a stable complex with free hemoglobin released from old red blood cells or during episodes of hemolysis, thus preventing iron loss and renal damage (1, 2). Haptoglobin consists of two chains, the ␣-chain and the ␤-chain, which are derived from a single polypeptide after proteolytic cleavage (3). The ␣-chain exists in two …