Cells per 16106 blood B 
lymphocytes [40,41]. Recently, EBV+ B lymphocytes undergoing germinal center reaction in human tonsils were shown to depend on a balance between proliferation and cell death, resulting in a stable number of infected cells [41]. The long-term cultures described here used the CD40-CD154 interaction, which is a central player in the germinal center reaction [12] and thus might result in a similar persistence of EBV+ cells without enlarged frequency. Besides, the fact that our cultures did not show oligoclonal but polyclonal patterns, suggests that the EBV+ B lymphocytes were not advantaged during the long-term expansion. The concept of human polyclonal antibodies is still a perspective for the future development of therapeutic antibodies [8]. A few years ago, transgenic animals were proposed as factories to replace the immunized polyclonal antibodies prepared from human orLarge-Scale Expansion of Human B LymphocytesTable 1. Human polyclonal IgG interacting proteins using a protein array.Signal1 IgG 7064 6499 4253 3891 3499 2887 2714 2707 2442 1854 1807 1687 1535 1491 1487 1259 1197 1188 1160 1109 1057 1041 1018 1015 CV1 ( ) 2 4 1 2 4 3 3 6 17 3 16 4 12 0 6 3 8 6 1 2 4 1 2Accession No. NM_002903.1 NM_004987.3 NM_133491.2 BC026346.1 PV3850 PV3836 BC017865.1 NM_018184.1 BC020229.1 NM_014288.2 NM_017614.3 NM_002150.1 BC036723.1 BC016768.1 PV3144 NM_007030.1 BC018929.1 NM_018246.1 NM_001007246.1 NM_138565.1 NM_138809.1 NM_004450.1 NM_152328.3 NM_133265.IgG/neg1 345 24 41 71 8 1155 10 7 71 3 2157 427 74 507 450 24 2 5 4 2 8 5 2Description2 recoverin (RCVRN) (*) LIM and senescent cell antigen-like-containing domain protein 1 (*) 16574785 (#) spermidine/spermine N1-acetyltransferase 2 (SAT2 family with JSI124 sequence similarity 84, member A (FAM84A) (*) casein kinase 1, alpha 1 (CSNK1A1), transcript variant 1 inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta (IKBKB) Fc fragment of IgG, low affinity IIIa, receptor (CD16a) (FCGR3A) (*) (#) ADP-ribosylation factor-like 8B (ARL8B) (#) arylsulfatase D (ARSD) (#) centromere protein R (#) betaine-homocysteine methyltransferase 2 (BHMT2) 4-hydroxyphenylpyruvate dioxygenase Fc fragment of IgG, low affinity IIIa, receptor (CD16a) (FCGR3A) (#) nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) neurotrophic tyrosine kinase, receptor, type 1 (NTRK1), transcript variant 3 tubulin polymerization promoting protein (TPPP) pleckstrin homology-like domain, family A, member 1 (PHLDA1) (#) coiled-coil domain containing 25 (CCDC25) bromodomain and WD 298690-60-5 web repeat domain containing 1 (BRWD1), transcript variant 3 cortactin (CTTN), transcript variant 2 (#) carboxymethylenebutenolidase homolog enhancer of rudimentary homolog (Drosophila) (ERH) adenylosuccinate synthase like 1 (ADSSL1), transcript variant 2 (#) angiomotin (AMOT) (#)1 Data present the IgG signal (1.0 mg/mL; threshold .1000) corresponding to background subtracted pixel intensity value (RFU), the 12926553 CV associated with the duplicate spots for each protein and the fold increase between IgG and negative control signals. 2 (*) Indicated significant interaction when IgG was adjusted to 0.1 mg/ml concentration (Threshold .500 RFU). 3 (#) Indicated significant interaction with a commercial intravenous immunoglobulin preparation (IVIg) adjusted to 1.0 mg/mL (Threshold .1000 RFU). doi:10.1371/journal.pone.0051946.tanimal plasma [42]. Polyclonal human antibodies have indeed been produced in transgenic cow and were reported to effici.Cells per 16106 blood B lymphocytes [40,41]. Recently, EBV+ B lymphocytes undergoing germinal center reaction in human tonsils were shown to depend on a balance between proliferation and cell death, resulting in a stable number of infected cells [41]. The long-term cultures described here used the CD40-CD154 interaction, which is a central player in the germinal center reaction [12] and thus might result in a similar persistence of EBV+ cells without enlarged frequency. Besides, the fact that our cultures did not show oligoclonal but polyclonal patterns, suggests that the EBV+ B lymphocytes were not advantaged during the long-term expansion. The concept of human polyclonal antibodies is still a perspective for the future development of therapeutic antibodies [8]. A few years ago, transgenic animals were proposed as factories to replace the immunized polyclonal antibodies prepared from human orLarge-Scale Expansion of Human B LymphocytesTable 1. Human polyclonal IgG interacting proteins using a protein array.Signal1 IgG 7064 6499 4253 3891 3499 2887 2714 2707 2442 1854 1807 1687 1535 1491 1487 1259 1197 1188 1160 1109 1057 1041 1018 1015 CV1 ( ) 2 4 1 2 4 3 3 6 17 3 16 4 12 0 6 3 8 6 1 2 4 1 2Accession No. NM_002903.1 NM_004987.3 NM_133491.2 BC026346.1 PV3850 PV3836 BC017865.1 NM_018184.1 BC020229.1 NM_014288.2 NM_017614.3 NM_002150.1 BC036723.1 BC016768.1 PV3144 NM_007030.1 BC018929.1 NM_018246.1 NM_001007246.1 NM_138565.1 NM_138809.1 NM_004450.1 NM_152328.3 NM_133265.IgG/neg1 345 24 41 71 8 1155 10 7 71 3 2157 427 74 507 450 24 2 5 4 2 8 5 2Description2 recoverin (RCVRN) (*) LIM and senescent cell antigen-like-containing domain protein 1 (*) 16574785 (#) spermidine/spermine N1-acetyltransferase 2 (SAT2 family with sequence similarity 84, member A (FAM84A) (*) casein kinase 1, alpha 1 (CSNK1A1), transcript variant 1 inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta (IKBKB) Fc fragment of IgG, low affinity IIIa, receptor (CD16a) (FCGR3A) (*) (#) ADP-ribosylation factor-like 8B (ARL8B) (#) arylsulfatase D (ARSD) (#) centromere protein R (#) betaine-homocysteine methyltransferase 2 (BHMT2) 4-hydroxyphenylpyruvate dioxygenase Fc fragment of IgG, low affinity IIIa, receptor (CD16a) (FCGR3A) (#) nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) neurotrophic tyrosine kinase, receptor, type 1 (NTRK1), transcript variant 3 tubulin polymerization promoting protein (TPPP) pleckstrin homology-like domain, family A, member 1 (PHLDA1) (#) coiled-coil domain containing 25 (CCDC25) bromodomain and WD repeat domain containing 1 (BRWD1), transcript variant 3 cortactin (CTTN), transcript variant 2 (#) carboxymethylenebutenolidase homolog 
enhancer of rudimentary homolog (Drosophila) (ERH) adenylosuccinate synthase like 1 (ADSSL1), transcript variant 2 (#) angiomotin (AMOT) (#)1 Data present the IgG signal (1.0 mg/mL; threshold .1000) corresponding to background subtracted pixel intensity value (RFU), the 12926553 CV associated with the duplicate spots for each protein and the fold increase between IgG and negative control signals. 2 (*) Indicated significant interaction when IgG was adjusted to 0.1 mg/ml concentration (Threshold .500 RFU). 3 (#) Indicated significant interaction with a commercial intravenous immunoglobulin preparation (IVIg) adjusted to 1.0 mg/mL (Threshold .1000 RFU). doi:10.1371/journal.pone.0051946.tanimal plasma [42]. Polyclonal human antibodies have indeed been produced in transgenic cow and were reported to effici.
