Transfer of Bovine J-Blood-Group Determinant onto Erythrocytes: Isolation and Identification of a Blocker

Abstract

The bovine J-blood-group determinant is transferred from a serum glycoprotein to an erythrocyte membrane lipid by incubation in vitro. This transfer is inhibited by a lipid (called 'blocker') occurring in bovine and human serum, in other bovine and human tissues, yeast and plant tissues.The blocker was isolated from bovine spleen and identified as phosphatidylserine. Moreover, phosphatidylinositol acts as a blocker, while a variety of other phospholipids, glycosphingolipids and neutral lipids have no function as blockers. Mild alkaline deacylation deletes the blocker activity of both phosphatidylserine and phosphatidylinositol. Methyl esters of these phospholipids, or exchange of the amino group for a hydroxyl group in phosphatidylserine or N-benzoylation of phosphatidylserine, do not affect the blocker function. The blocker function of phosphatidylinositol is lost after periodate oxidation.The blocker reacts with the J-containing serum protein, not with the erythrocyte membrane. After preincubation of the J-positive serum protein with the blocker and reextraction of excess blocker, the serum protein remains J-positive, but is then unable to transfer the J determinant to the erythrocyte membrane.There are blood-group-active substances in various mammalian species that are primarily dissolved in the blood plasma and secondarily transferred onto the erythrocyte membranes [I 1. The bovine J-bloodgroup active substance is one of these [2]. Since the transfer of J activity from J-positive serum to Jnegative bovine erythrocytes can be studied in vitro [3,4], the bovine J blood-group system can be used as a model system for the study of exchange of carbohydrate units between plasma and erythrocyte membrane. A similar exchange may possibly occur also in various mammalian species [5,6].The J-blood-group activity of adult cattle is found in a serum glycolipid fraction [7] as well as in a serum nonlipid fraction, probably a glycoprotein [S]. It was shown recently [3,4] that the J determinant is transferred from the serum nonlipid to an erythrocyte membrane lipid by incubation in vitro. This transfer probably involves splitting of a covalent linkage at the serum glycoprotein, transfer of the J determinant (a carbohydrate unit) to a lipidic receptor at the erythrocyte membrane and forming of a new covalent linkage at a membrane glycolipid [4].It was established that the transfer of J activity from serum to erythrocyte membranes is inhibited by a substance (called 'blocker') present in bovine serum [9]. The blocker was shown to be a polar lipid 141. Isolation and identification of the blocker is described in this paper. MATERIALS AND METHODSBovine blood was obtained from the local slaughter house and classified J-negative (j") and J-positive (J"'), respectively, by testing small pilot samples of blood for J activity with anti-J serum that had been checked in international comparison tests. Spleens of J-negative cattle were also obtained from the slaughter house. Human blood (blood group 0) was obtained from the Gottingen bl...

The Transfer of Bovine J Blood‐Group Activity to Erythrocytes: Kinetic Studies

“…However, the transfer of J activity from serum lipids to erythrocytes is very inefficient, if at all detectable. This poor transfer is probably due to the presence of a blocking substance (l), which is a mixture of phospholipids (14).…”

The transfer of bovine J blood group activity to erythrocytes: evidence of a transferable and of a non‐transferable J in serum

“…However, the transfer of J activity from the serum lipid fraction to erythrocytes is very inefficient, if at all detectable. This poor transfer is probably due to the presence of a blocking substance (Blakeslee & Stone, 1971) which is a mixture of phospholipids (Stephan & Thiele, 1978).The solid residue which served as the J donor in earlier experiments was almost insoluble in water or saline. Therefore, attempts were made to prepare a soluble Jactive fraction from this residue.…”

“…However, the transfer of J activity from the serum lipid fraction to erythrocytes is very inefficient, if at all detectable. This poor transfer is probably due to the presence of a blocking substance (Blakeslee & Stone, 1971) which is a mixture of phospholipids (Stephan & Thiele, 1978).…”