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designation will be used for the 12E7 antigen. CD99 was first detected by 12E7, a monoclonal antibody made in response to a T-cell line, and was initially thought to be a ‘thymus-leukaemia’ marker antigen [41]. Many similar antibodies were made which reacted with different epitopes of the same molecule [see 42]. Independently, CD99 was identified as E2, a T-cell adhesion molecule, and as a marker antigen for Ewing’s tumours [see 40]. CD99 is expressed on many tissues including red cells. By somatic cell hybridization and biochemical studies, Goodfellow and his colleagues have shown that MIC2, the structural locus encoding the 12E7 antigen, is located on the short arm of the X chromosome and on the short arm of the Y chromosome within the pairing regions [43]. MIC2 has been cloned [44]. XG is X-borne. On red cells, CD99 expression is a quantitative polymorphism [45]. Family studies proved that this polymorphism is also caused by regulator genes on X and Y chromosomes. XG appears to be the regulator on the X [46]. There is variation in CD99 expression on cells other than red cells. In a recent publication, CD99 was found on all haemopoeitic cells but was variably expressed during leucocyte differentiation [40]. Use of different monoclonal antibodies and variability of expression during maturation offered an explanation for the previous apparently contradictory findings by different laboratories. Both Xga and CD99 are sialoglycoproteins [47,48,49]. These glycoproteins differ in Mr and in their sialic acid content [49]. Immunostaining of separated membrane components with 12E7 and similar antibodies had demonstated that the MIC2 gene product was a 30-32 kD protein. 12E7 also bound to an intracellular band of 28 kD which was found in mouse cell lines in addition to human cell lines, platelets, lymphocytes and red cells but it was not encoded by the MIC2 gene [47]. Immunoblotting assays have shown that Xga was associated with two diffuse bands of 22-25 kD and 26.5-29 kD [49]. These findings supported the evidence that Xga and CD99 were products of different structural loci. However, XG appears to regulate CD99 expression on red cells and Latron and colleagues found that purified CD99 protein inhibited binding of 12E7 and of anti-Xga to red cells [48]. We have studied the immunochemical relationship of Xga and CD99 [50]. One approach was immunoprecipitation of membrane components from biotin labelled cells. Bands are detected by chemiluminescence via peroxidase-conjugated avidin. The 32 kD protein of CD99 was visualised by this technique and the quantitative polymorphism was also demonstrated since the 32 kD band is seen on X-ray film after 2 minutes in membranes
DOI link for designation will be used for the 12E7 antigen. CD99 was first detected by 12E7, a monoclonal antibody made in response to a T-cell line, and was initially thought to be a ‘thymus-leukaemia’ marker antigen [41]. Many similar antibodies were made which reacted with different epitopes of the same molecule [see 42]. Independently, CD99 was identified as E2, a T-cell adhesion molecule, and as a marker antigen for Ewing’s tumours [see 40]. CD99 is expressed on many tissues including red cells. By somatic cell hybridization and biochemical studies, Goodfellow and his colleagues have shown that MIC2, the structural locus encoding the 12E7 antigen, is located on the short arm of the X chromosome and on the short arm of the Y chromosome within the pairing regions [43]. MIC2 has been cloned [44]. XG is X-borne. On red cells, CD99 expression is a quantitative polymorphism [45]. Family studies proved that this polymorphism is also caused by regulator genes on X and Y chromosomes. XG appears to be the regulator on the X [46]. There is variation in CD99 expression on cells other than red cells. In a recent publication, CD99 was found on all haemopoeitic cells but was variably expressed during leucocyte differentiation [40]. Use of different monoclonal antibodies and variability of expression during maturation offered an explanation for the previous apparently contradictory findings by different laboratories. Both Xga and CD99 are sialoglycoproteins [47,48,49]. These glycoproteins differ in Mr and in their sialic acid content [49]. Immunostaining of separated membrane components with 12E7 and similar antibodies had demonstated that the MIC2 gene product was a 30-32 kD protein. 12E7 also bound to an intracellular band of 28 kD which was found in mouse cell lines in addition to human cell lines, platelets, lymphocytes and red cells but it was not encoded by the MIC2 gene [47]. Immunoblotting assays have shown that Xga was associated with two diffuse bands of 22-25 kD and 26.5-29 kD [49]. These findings supported the evidence that Xga and CD99 were products of different structural loci. However, XG appears to regulate CD99 expression on red cells and Latron and colleagues found that purified CD99 protein inhibited binding of 12E7 and of anti-Xga to red cells [48]. We have studied the immunochemical relationship of Xga and CD99 [50]. One approach was immunoprecipitation of membrane components from biotin labelled cells. Bands are detected by chemiluminescence via peroxidase-conjugated avidin. The 32 kD protein of CD99 was visualised by this technique and the quantitative polymorphism was also demonstrated since the 32 kD band is seen on X-ray film after 2 minutes in membranes
designation will be used for the 12E7 antigen. CD99 was first detected by 12E7, a monoclonal antibody made in response to a T-cell line, and was initially thought to be a ‘thymus-leukaemia’ marker antigen [41]. Many similar antibodies were made which reacted with different epitopes of the same molecule [see 42]. Independently, CD99 was identified as E2, a T-cell adhesion molecule, and as a marker antigen for Ewing’s tumours [see 40]. CD99 is expressed on many tissues including red cells. By somatic cell hybridization and biochemical studies, Goodfellow and his colleagues have shown that MIC2, the structural locus encoding the 12E7 antigen, is located on the short arm of the X chromosome and on the short arm of the Y chromosome within the pairing regions [43]. MIC2 has been cloned [44]. XG is X-borne. On red cells, CD99 expression is a quantitative polymorphism [45]. Family studies proved that this polymorphism is also caused by regulator genes on X and Y chromosomes. XG appears to be the regulator on the X [46]. There is variation in CD99 expression on cells other than red cells. In a recent publication, CD99 was found on all haemopoeitic cells but was variably expressed during leucocyte differentiation [40]. Use of different monoclonal antibodies and variability of expression during maturation offered an explanation for the previous apparently contradictory findings by different laboratories. Both Xga and CD99 are sialoglycoproteins [47,48,49]. These glycoproteins differ in Mr and in their sialic acid content [49]. Immunostaining of separated membrane components with 12E7 and similar antibodies had demonstated that the MIC2 gene product was a 30-32 kD protein. 12E7 also bound to an intracellular band of 28 kD which was found in mouse cell lines in addition to human cell lines, platelets, lymphocytes and red cells but it was not encoded by the MIC2 gene [47]. Immunoblotting assays have shown that Xga was associated with two diffuse bands of 22-25 kD and 26.5-29 kD [49]. These findings supported the evidence that Xga and CD99 were products of different structural loci. However, XG appears to regulate CD99 expression on red cells and Latron and colleagues found that purified CD99 protein inhibited binding of 12E7 and of anti-Xga to red cells [48]. We have studied the immunochemical relationship of Xga and CD99 [50]. One approach was immunoprecipitation of membrane components from biotin labelled cells. Bands are detected by chemiluminescence via peroxidase-conjugated avidin. The 32 kD protein of CD99 was visualised by this technique and the quantitative polymorphism was also demonstrated since the 32 kD band is seen on X-ray film after 2 minutes in membranes
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