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Boston University
Publishes on Monoclonal and Polyclonal Antibodies Research, T-cell and B-cell Immunology, Enzyme function and inhibition. 23 papers and 2.2k citations.
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The complement system membrane cofactor protein (MCP) CD46 serves as a C3b/C4b inactivating factor for the protection of host cells from autologous complement attack and as a receptor for measles virus (MV). MCP consists of four short consensus repeats (SCR) which are the predominant extracellular structural motif. In the present study, we determined which of the four SCR of MCP contribute to its function using Chinese hamster ovary cell clones expressing each SCR deletion mutants. The results were as follows: 1) SCR1 and SCR2 are mainly involved in MV binding and infection; 2) SCR2, SCR3, and SCR4 contribute to protect Chinese hamster ovary cells from human alternative complement pathway-mediated cytolysis; and 3) SCR2 and SCR3 are essential for protection of host cells from the classical complement pathway. These results on cell protective activity of the mutants against the human classical and the alternative complement pathways were compatible with factor I-mediated inactivation profiles of C4b and C3b, respectively, in the fluid-phase assay using solubilized mutants and factor I; the results were mostly consistent with those reported by Adams et al. (Adams, E. M., Brown, M. C., Nunge, M., Krych, M., and Atkinson, J. P.(1991) J. Immunol. 147, 3005-3011). SCR2 and SCR3 were required for C3b and C4b inactivation, and SCR4-deleted MCP showed weak cofactor activity for C4b cleavage but virtually no cofactor activity for C3b cleavage. The functional domains of MCP for the three natural ligands C3b, C4b, and MV, therefore, map to different, although partly overlapping, SCR domains. The complement system membrane cofactor protein (MCP) CD46 serves as a C3b/C4b inactivating factor for the protection of host cells from autologous complement attack and as a receptor for measles virus (MV). MCP consists of four short consensus repeats (SCR) which are the predominant extracellular structural motif. In the present study, we determined which of the four SCR of MCP contribute to its function using Chinese hamster ovary cell clones expressing each SCR deletion mutants. The results were as follows: 1) SCR1 and SCR2 are mainly involved in MV binding and infection; 2) SCR2, SCR3, and SCR4 contribute to protect Chinese hamster ovary cells from human alternative complement pathway-mediated cytolysis; and 3) SCR2 and SCR3 are essential for protection of host cells from the classical complement pathway. These results on cell protective activity of the mutants against the human classical and the alternative complement pathways were compatible with factor I-mediated inactivation profiles of C4b and C3b, respectively, in the fluid-phase assay using solubilized mutants and factor I; the results were mostly consistent with those reported by Adams et al. (Adams, E. M., Brown, M. C., Nunge, M., Krych, M., and Atkinson, J. P.(1991) J. Immunol. 147, 3005-3011). SCR2 and SCR3 were required for C3b and C4b inactivation, and SCR4-deleted MCP showed weak cofactor activity for C4b cleavage but virtually no cofactor activity for C3b cleavage. The functional domains of MCP for the three natural ligands C3b, C4b, and MV, therefore, map to different, although partly overlapping, SCR domains. INTRODUCTIONHuman membrane cofactor protein (MCP)1( 1The abbreviations used are: MCPmembrane cofactor protein (CD46)DACMN-(dimethylamino-4-methylcoumarinyl)maleimideDAFdecay-accelerating factor (CD55)mAbmonoclonal antibodyAbantibodyMVmeasles virusSCRshort consensus repeat (DSCR1 means the SCR1-deleted form)STserine/threonine-rich domainCYTcytoplasmic tailPAGEpolyacrylamide gel electrophoresisCHOChinese hamster ovaryDMEMDulbecco's modified Eagle's mediumpfuplaque-forming unit(s).) CD46 was first identified as a C3b-binding protein (1Cole J.L. Housley Jr., G.A. Dykman T.R. MacDermott R.P. Atkinson J.P. Proc. Natl. Acad. Sci. U. S. A. 1985; 82: 859-863Crossref PubMed Scopus (140) Google Scholar) distinct from other membrane complement-associated proteins such as CR1 (CD35), CR2 (CD21), and decay-accelerating factor (DAF, CD55) (reviewed in Ref. 2). MCP inactivates cell-bound C3b/C4b, acting as a cofactor for plasma protease factor I(3Seya T. Turner J.R. Atkinson J.P. J. Exp. Med. 1986; 163: 837-855Crossref PubMed Scopus (321) Google Scholar, 4Seya T. Atkinson J.P. Biochem. J. 1989; 264: 581-588Crossref PubMed Scopus (122) Google Scholar), and protects host cells from complement-mediated cell damage(5Seya T. Hara T. Matsumoto M. Sugita Y. Akedo H. J. Exp. Med. 1990; 172: 1673-1680Crossref PubMed Scopus (101) Google Scholar, 6Lublin D.M. Coyne K.E. J. Exp. Med. 1991; 174: 35-44Crossref PubMed Scopus (98) Google Scholar, 7Oglesby T.J. Allen C.J. Liszewski M.K. White D.J.G. Atkinson J.P. J. Exp. Med. 1993; 175: 1547-1551Crossref Scopus (132) Google Scholar). This molecule composed of an amino terminus of four short consensus repeating units (SCR), a Ser/Thr (ST)-rich domain, 13 amino acids of unknown significance, a transmembrane region, and a cytoplasmic tail (CYT)(8Lublin D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google Scholar). The region responsible for complement regulation is the SCR(9Adams E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar, 10Matsumoto M. Seya T. Nagasawa S. Biochem. J. 1992; 281: 493-499Crossref PubMed Scopus (35) Google Scholar). The structural gene for MCP maps to 1q32(8Lublin D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google Scholar), where the genes of complement regulatory proteins, C4b-binding protein, DAF, CR1, CR2, and factor H, are clustered(11Bora N. Lublin D.M. Kumar V. Hockett R.D. Holers V.M. Atkinson J.P. J. Exp. Med. 1989; 169: 597-602Crossref PubMed Scopus (39) Google Scholar). MCP is a member of the regulator of complement activation gene family.Naniche et al.(12Naniche D. Varior-Krishnan G. Cervoni F. Wild T.F. Rossi B. Rabourdin-Combe C. Gerlier D. J. Virol. 1993; 67: 6025-6032Crossref PubMed Google Scholar) and Dorig et al.(13Dorig R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar) have suggested that MCP also serves as a receptor for measles virus (MV). MV, however, has no C3b-like molecules on its envelope. H protein of MV is thought to act as a ligand for target cell receptors, whereas F protein then induces viral-cell fusion(14Richardson C.D. Scheid A. Choppin P.W. Virology. 1980; 105: 205-222Crossref PubMed Scopus (234) Google Scholar, 15Wild T.F. Malvoisin E. Buckland R. J. Gen. Virol. 1991; 72: 439-442Crossref PubMed Scopus (209) Google Scholar). Indeed, MV can infect human and various monkey species, the tropism correlating with the expression of MCP(13Dorig R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar, 16Nickells M.W. Atkinson J.P. J. Immunol. 1990; 144: 4262-4267PubMed Google Scholar).There are many MCP phenotypes, which are distinguishable on SDS-PAGE (17-19). This polymorphism is caused by alternative splicing of mRNA encoding the ST-rich and CYT regions(17Post T.W. Liszewski M.K. Adams E.M. Tedja I. Miller E.A. Atkinson J.P. J. Exp. Med. 1991; 174: 93-102Crossref PubMed Scopus (146) Google Scholar). CHO cell clones expressing MCP variants with a variety of ST-rich (20Iwata K. Seya T. Ueda S. Ariga H. Nagasawa S. Biochem. J. 1994; 304: 169-175Crossref PubMed Scopus (34) Google Scholar) or CYT domains (21Manchester M. Liszewski M.K. Atkinson J.P. Oldstone M.B.A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 2161-2165Crossref PubMed Scopus (154) Google Scholar) have been reported to become permissive to MV. Thus, the MV-binding site on MCP must be located within the SCR. The MV-binding site and its structural relationship to the complement-binding site, therefore, remain to be elucidated.In the present study, we established CHO transfectants expressing various SCR deletion mutants of MCP and mapped the functional domains for complement regulation and MV binding.MATERIALS AND METHODSCells, Antibodies, and ProteinsCHO cells were obtained from American Type Culture Collection (ATCC). Vero cells, green monkey erythrocytes, and MV, a modified Nagahata strain(22Wong T. Ayata M. Ueda S. Hirano A. J. Virol. 1991; 65: 2191-2199Crossref PubMed Google Scholar), were obtained from the Research Institute for Microbial Diseases, Osaka University. Monoclonal antibodies (mAbs) against MCP, M75, M160, and M177, were produced in our laboratory(23Seya T. Hara T. Matsumoto M. Akedo H. J. Immunol. 1990; 145: 238-245PubMed Google Scholar), E4.3 (24Sparrow R. McKenzie I.F.C. Hum. Immunol. 1983; 7: 1-6Crossref PubMed Scopus (37) Google Scholar) was from Dr. B. Loveland (Austin Institute, Melbourne, Australia), and other mAbs were reported previously(25Pesando J.M. Hoffman P. Abed M. J. Immunol. 1986; 137: 3689-3695PubMed Google Scholar, 26Stern P.L. Beresford N. Thompson S. Johnson P.M. Webb P.D. Hole N. J. Immunol. 1986; 137: 1604-1609PubMed Google Scholar). Serum from a patient with subacute sclerosing panencephalitis containing a high titer of anti-MV Ab was obtained from Dr. M. B. A. Oldstone (The Scripps Research Institute, La Jolla, CA)(27Yanagi Y. Cubitt B.A. Oldstone M.B.A. Virology. 1992; 187: 280-289Crossref PubMed Scopus (81) Google Scholar).Complement C3(28Nagasawa S. PubMed Scopus Google Scholar), S. C. J. Immunol. 1980; Google Scholar), factor T. Nagasawa S. J. Biochem. 1985; PubMed Scopus Google Scholar), and factor S. C. J. Immunol. 1980; Google Scholar) were from human plasma as C3b and C4b were S. C. J. Immunol. 1980; Google Scholar, T. Nagasawa S. J. Biochem. 1985; PubMed Scopus Google Scholar) and with an T. M. H. Atkinson J.P. J. Biochem. 1990; PubMed Scopus Google Scholar). The C3b and C4b have been as for factor and T. M. H. Atkinson J.P. J. Biochem. 1990; PubMed Scopus Google Scholar, T. Matsumoto M. I. R. Seya T. J. Biochem. 1992; PubMed Scopus Google Scholar). were obtained as follows: F and and of SCR of MCP in CHO of D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google Scholar) was using a In S. the encoding a SCR to amino acids of MCP, in to its amino D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google were the was to SCR1 of were determined to a the amino the amino and the amino The of the were on a and MCP were the expression A. K. Seya T. Matsumoto M. Ariga H. Atkinson J.P. Nagasawa S. J. Immunol. 1993; Google Scholar). The were on the cells were with containing MCP and of gene K. H. Cell. PubMed Scopus Google Scholar) by J. T. Scholar). The CHO cells were for in in an of The cells were to the containing of for The were with and in The CHO cells were by J. T. Scholar). The expression of mutants was by using M177, and and protein on the cells were by as using and and CHO cells, with and were used as was as H. T. J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). MCP and its mutants were solubilized from transfectants as reported T. Turner J.R. Atkinson J.P. J. Exp. Med. 1986; 163: 837-855Crossref PubMed Scopus (321) Google Scholar). The proteins were by SDS-PAGE and with a against The for were in M. Seya T. Nagasawa S. Biochem. J. 1992; 281: 493-499Crossref PubMed Scopus (35) Google was with of and with of F. for of F was and for an was with an of and with of for of and of F were and for The was with an of F and for an The were by SDS-PAGE and with which fluid-phase assay was used C3b or C4b and factor were for with various of MCP or its SCR deletion which were as The solubilized from cells were by T. Turner J.R. Atkinson J.P. J. Exp. Med. 1986; 163: 837-855Crossref PubMed Scopus (321) Google Scholar), and the of and MCP were by T. S. H. Y. Matsumoto M. Seya T. Exp. Immunol. 1992; PubMed Scopus Google Scholar). SCR2 and SCR3 deletion mutants be in the of the mutants were from the of the mutants on the CHO cells the to be the as that of the obtained MCP of and was used as an MCP of and of were to the and to the The were by SDS-PAGE and the of C3b to and of C4b to were determined by as T. M. H. Atkinson J.P. J. Biochem. 1990; PubMed Scopus Google Scholar, T. Matsumoto M. I. R. Seya T. J. Biochem. 1992; PubMed Scopus Google Scholar). activity was mostly by the of T. Hara T. Matsumoto M. Sugita Y. Akedo H. J. Exp. Med. 1990; 172: 1673-1680Crossref PubMed Scopus (101) Google Scholar), that the MCP was a cofactor in CHO cells of CHO cell Ab was used as a A. K. Seya T. Matsumoto M. Ariga H. Atkinson J.P. Nagasawa S. J. Immunol. 1993; Google Scholar), and the complement for the classical and the alternative pathways were human with and human with containing and the cells were on the cells were with in for three with the cells were with Ab for then of complement were The were for and the were in a was as were in to be for MV binding were from by the of of containing containing cells were for with of MV in modified Eagle's containing three with cells were for with of Y. Cubitt B.A. Oldstone M.B.A. Virology. 1992; 187: 280-289Crossref PubMed Scopus (81) Google Scholar). three with of cells were with of The of the MV H protein in each CHO cell were by of MV cell clones with or a variety of MCP mutants were in for and with MV we Y. Cubitt B.A. Oldstone M.B.A. Virology. 1992; 187: 280-289Crossref PubMed Scopus (81) Google Scholar) and the CHO cell and The were and the of the CHO cell transfectants R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar) were no was our of MV within were a of the cells were and the MV titer was determined using Vero cells by the and of SCR on CHO expression of the MCP mutants and were by SCR deletion mutants were proteins and on the CHO cells The expression of MCP mutants were on clones used for the the of which was on the the of E4.3 was mapped in SCR1 of consistent with the results of a E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar). the of was mapped in SCR2 of was with mAbs against MCP, and the results are and on MCP of mAbs in a suggested that the MCP has an of consistent with that of the reported D.M. Coyne K.E. J. Exp. Med. 1991; 174: 35-44Crossref PubMed Scopus (98) Google Scholar, A. K. Seya T. Matsumoto M. Ariga H. Atkinson J.P. Nagasawa S. J. Immunol. 1993; Google Scholar). The of and mutants were and The present results those of that SCR1 and SCR2 are The on SDS-PAGE of and from the The were a on SDS-PAGE and was by by Thus, on CHO cells the protein consists of with a of and a mutants on SDS-PAGE to be of the MCP regulatory of the mutants were determined by fluid-phase factor T. M. H. Atkinson J.P. J. Biochem. 1990; PubMed Scopus Google Scholar, T. Matsumoto M. I. R. Seya T. J. Biochem. 1992; PubMed Scopus Google Scholar). cells activity by cells was the C3b as a and mutants showed no cofactor activity to the MCP, whereas its activity results were obtained with C4b, that the cofactor activity for C4b cleavage in the C4b inactivation the of of other in the C4b cell protection assay from human complement was with CHO cells with the mutants and the complement for the classical and the alternative pathways CHO cell clones expressing MCP were used as expression of MCP was as high as that of and the other expression of MCP was to those of and The as protective activity from complement attack as a from the MCP on the CHO cells, and MCP cells from the pathways with The and mutants showed no protective activity from the and the virtually no on alternative pathway-mediated cell protective activity against the classical pathway. Thus, the of cell protection in the mutants were consistent with factor The results are in a The of MCP for MV binding assay was by was in CHO cells expressing and but in those expressing or The of MV binding were in the is a for MV of CHO cells expressing MCP(13Dorig R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar). In study, were the and the of each of MV was to the titer of The of MV for are The results those of the MV binding These results suggested that SCR1 and SCR2 are the domains essential for MV of the SCR1 and SCR2 domains for MV was also by the with SCR2 was mAbs and MV in CHO transfectants and Vero MV in CHO but Vero This be to or a in SCR2 to the binding of to of MV in MCP CHO in CHO transfectants expressing and as as whereas no in CHO transfectants expressing or mutants. The results were by of MV H protein by using subacute sclerosing panencephalitis and against MV H. The results the that the SCR1 and SCR2 domains are essential for MV and that MV is of deletion of SCR3 or which of the four SCR domains of MCP contribute to the cofactor activity for factor I-mediated cleavage of C3b and C4b, the protection of host cells from complement-mediated and MV binding using deletion mutants. In 1) SCR1 and SCR2 are mainly involved in MV binding and infection; 2) SCR2, SCR3, and SCR4 C3b inactivation by factor I; and 3) SCR2 and SCR3 are essential for factor I-mediated inactivation of The are to those reported by Adams et E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar) and et T.J. Allen C.J. Liszewski M.K. White D.J.G. Atkinson J.P. Immunol. 1993; Google Scholar), that the weak cofactor activity for factor I-mediated C4b cleavage. also determined the domains responsible for C3b and C4b E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar). results with that the three ligands of MCP, C3b, C4b, and MV, to of SCR and distinct of MCP is a receptor with classical and alternative complement regulatory and MV binding our expression system using CHO cells, in in the of the This is the in a cell expression system reported by Adams et E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar), which the results E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar, T.J. Allen C.J. Liszewski M.K. White D.J.G. Atkinson J.P. Immunol. 1993; Google Scholar) and our present the of the of the protein the that our cofactor activity for C4b and that CHO cells expressing are to MV those expressing or is that MCP molecules are in cell In a variety of MCP variants to cell and have been T.W. Liszewski M.K. Adams E.M. Tedja I. Miller E.A. Atkinson J.P. J. Exp. Med. 1991; 174: 93-102Crossref PubMed Scopus (146) Google Scholar, McKenzie I.F.C. J. Immunol. 1992; PubMed Scopus (98) Google Scholar, Loveland B. McKenzie I.F.C. Immunol. 1993; PubMed Scopus Google and such as (reviewed in Ref. and M.A. J. Exp. Med. 1991; 174: PubMed Scopus Google Scholar) the host complement system to the of on and by the cells complement et al.(12Naniche D. Varior-Krishnan G. Cervoni F. Wild T.F. Rossi B. Rabourdin-Combe C. Gerlier D. J. Virol. 1993; 67: 6025-6032Crossref PubMed Google Scholar) suggested for MV, but no has been The that the SCR1 is responsible for MV binding but for the C3b/C4b inactivation the of C3b in are mAbs that the SCR1 of MCP of for an however, MV in Vero cells and CHO be that the for mAbs in SCR1 are in MV MV in CHO The mAbs reported by et D. Wild T.F. Rabourdin-Combe C. Gerlier D. J. Gen. Virol. 1992; PubMed Scopus Google Scholar) MV but have been with to the of complement regulatory P. M. C. J. Immunol. 1988; PubMed Scopus Google Scholar), which the SCR3 or has been reported to C3b and C4b binding to MCP MV R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar). the binding of C3b/C4b and MV in MCP map in no reported to can MV binding and complement regulatory of and T. Hara T. Matsumoto M. Akedo H. J. Immunol. 1990; 145: 238-245PubMed Google Scholar) are the first mAbs to of were mapped in the SCR2 domain, which is for MV binding and C3b/C4b that mAbs and can MV in CHO transfectants but in Vero cells structural in the SCR domains of MCP human and MCP, CR2 and have been reported to be for the virus B. Holers V.M. J. 1990; Full Text PDF PubMed Google Scholar, A. M. M. J. Virol. 1991; 65: PubMed Google Scholar) and of the J.M. M. H. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: PubMed Scopus Google Scholar), The of molecules to be for virus to other virus S. I. A. Proc. Natl. Acad. Sci. U. S. A. 1991; PubMed Scopus Google Scholar). are many SCR proteins, which cell (reviewed in and by and 1990; PubMed Scopus Google Scholar). a for be for to SCR proteins as a which by are required to membrane of MCP was with each The were then with C3b and factor for in containing and were by SDS-PAGE activity was from the of the and by by each was that the of the to the in the of was of Vero or CHO cells in were for with each in then with MV a of of units determined on Vero cell for The cells were three and for the was a INTRODUCTIONHuman membrane cofactor protein (MCP)1( 1The abbreviations used are: MCPmembrane cofactor protein (CD46)DACMN-(dimethylamino-4-methylcoumarinyl)maleimideDAFdecay-accelerating factor (CD55)mAbmonoclonal antibodyAbantibodyMVmeasles virusSCRshort consensus repeat (DSCR1 means the SCR1-deleted form)STserine/threonine-rich domainCYTcytoplasmic tailPAGEpolyacrylamide gel electrophoresisCHOChinese hamster ovaryDMEMDulbecco's modified Eagle's mediumpfuplaque-forming unit(s).) CD46 was first identified as a C3b-binding protein (1Cole J.L. Housley Jr., G.A. Dykman T.R. MacDermott R.P. Atkinson J.P. Proc. Natl. Acad. Sci. U. S. A. 1985; 82: 859-863Crossref PubMed Scopus (140) Google Scholar) distinct from other membrane complement-associated proteins such as CR1 (CD35), CR2 (CD21), and decay-accelerating factor (DAF, CD55) (reviewed in Ref. 2). MCP inactivates cell-bound C3b/C4b, acting as a cofactor for plasma protease factor I(3Seya T. Turner J.R. Atkinson J.P. J. Exp. Med. 1986; 163: 837-855Crossref PubMed Scopus (321) Google Scholar, 4Seya T. Atkinson J.P. Biochem. J. 1989; 264: 581-588Crossref PubMed Scopus (122) Google Scholar), and protects host cells from complement-mediated cell damage(5Seya T. Hara T. Matsumoto M. Sugita Y. Akedo H. J. Exp. Med. 1990; 172: 1673-1680Crossref PubMed Scopus (101) Google Scholar, 6Lublin D.M. Coyne K.E. J. Exp. Med. 1991; 174: 35-44Crossref PubMed Scopus (98) Google Scholar, 7Oglesby T.J. Allen C.J. Liszewski M.K. White D.J.G. Atkinson J.P. J. Exp. Med. 1993; 175: 1547-1551Crossref Scopus (132) Google Scholar). This molecule composed of an amino terminus of four short consensus repeating units (SCR), a Ser/Thr (ST)-rich domain, 13 amino acids of unknown significance, a transmembrane region, and a cytoplasmic tail (CYT)(8Lublin D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google Scholar). The region responsible for complement regulation is the SCR(9Adams E.M. Brown M.C. Nunge M. Krych M. Atkinson J.P. J. Immunol. 1991; 147: 3005-3011PubMed Google Scholar, 10Matsumoto M. Seya T. Nagasawa S. Biochem. J. 1992; 281: 493-499Crossref PubMed Scopus (35) Google Scholar). The structural gene for MCP maps to 1q32(8Lublin D.M. Liszewski M.K. Post T.W. Arce M.A. Le Beau M.M. Rebentisch M.B. Lemons R.S. Seya T. Atkinson J.P. J. Exp. Med. 1988; 168: 181-194Crossref PubMed Scopus (172) Google Scholar), where the genes of complement regulatory proteins, C4b-binding protein, DAF, CR1, CR2, and factor H, are clustered(11Bora N. Lublin D.M. Kumar V. Hockett R.D. Holers V.M. Atkinson J.P. J. Exp. Med. 1989; 169: 597-602Crossref PubMed Scopus (39) Google Scholar). MCP is a member of the regulator of complement activation gene family.Naniche et al.(12Naniche D. Varior-Krishnan G. Cervoni F. Wild T.F. Rossi B. Rabourdin-Combe C. Gerlier D. J. Virol. 1993; 67: 6025-6032Crossref PubMed Google Scholar) and Dorig et al.(13Dorig R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar) have suggested that MCP also serves as a receptor for measles virus (MV). MV, however, has no C3b-like molecules on its envelope. H protein of MV is thought to act as a ligand for target cell receptors, whereas F protein then induces viral-cell fusion(14Richardson C.D. Scheid A. Choppin P.W. Virology. 1980; 105: 205-222Crossref PubMed Scopus (234) Google Scholar, 15Wild T.F. Malvoisin E. Buckland R. J. Gen. Virol. 1991; 72: 439-442Crossref PubMed Scopus (209) Google Scholar). Indeed, MV can infect human and various monkey species, the tropism correlating with the expression of MCP(13Dorig R.E. Marcil A. Chopra A. Richardson D. Cell. 1993; 75: 295-305Abstract Full Text PDF PubMed Scopus (864) Google Scholar, 16Nickells M.W. Atkinson J.P. J. Immunol. 1990; 144: 4262-4267PubMed Google Scholar).There are many MCP phenotypes, which are distinguishable on SDS-PAGE (17-19). This polymorphism is caused by alternative splicing of mRNA encoding the ST-rich and CYT regions(17Post T.W. Liszewski M.K. Adams E.M. Tedja I. Miller E.A. Atkinson J.P. J. Exp. Med. 1991; 174: 93-102Crossref PubMed Scopus (146) Google Scholar). CHO cell clones expressing MCP variants with a variety of ST-rich (20Iwata K. Seya T. Ueda S. Ariga H. Nagasawa S. Biochem. J. 1994; 304: 169-175Crossref PubMed Scopus (34) Google Scholar) or CYT domains (21Manchester M. Liszewski M.K. Atkinson J.P. Oldstone M.B.A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 2161-2165Crossref PubMed Scopus (154) Google Scholar) have been reported to become permissive to MV. Thus, the MV-binding site on MCP must be located within the SCR. The MV-binding site and its structural relationship to the complement-binding site, therefore, remain to be elucidated.In the present study, we established CHO transfectants expressing various SCR deletion mutants of MCP and mapped the functional domains for complement regulation and MV
ABLATIVE chemotherapy with allogeneic bone-marrow transplantation has become an accepted means of therapy for acute leukemia.1 It is the only treatment capable of producing long-term unmaintained remissions in patients with acute lymphoblastic leukemia who have had relapses during the course of conventional chemotherapy, and it has been advocated for acute myeloblastic leukemia in first remission.1 An initially unforeseen and rare form of failure of such therapy has been the relapse of leukemia in donor cells.2 3 4 5 We report here our experience with a patient with acute lymphoblastic leukemia who had a relapse after therapy with high-dose cyclophosphamide, total-body irradiation, and bone-marrow . . .