Ng these experiments. The Tgen period calculated between days 28 to 36 in all these cultures, corresponded to a mean of 51 h69 h (data not shown). Cell viability was also comparable from one cultured sample to another and maintained at an acceptable level, ranging from 93 to 80 at the end of the culture period (Figs. 2C and D). Overall, these culture conditions allowed a final expansion factor, based on the expansion rate and seeding cell numbers, ranging from 107 to 109 after 50 to 65 days.the secretion rate mean values for the ten experiments (Fig. 3D), the relative proportions of IgG1 (67 ), IgG2 (24 ), IgG3 (6 ) and IgG4 (3 ) were comparable to those reported in human serum, namely IgG1 60 615 , IgG2 30 65 , IgG3 7 62 and IgG4 3 61 [25,26]. The IgG total secretion recorded for each culture experiments ranged from 30 to 115 mg/mL (data not shown). Overall these data showed that long-term culture of IgG+ human B lymphocytes did not induce a bias in the secretion of IgG isotypes, which was consistent with the reported proportions in human blood.Expanded IgG+ B Lymphocytes are Polyclonal PopulationsThe degree of heterogeneity of secreted IgG molecules was assessed during the long-term culture by sampling culture supernatant at various time points and analyzing their patterns by isoelectrofocusing. Analysis of secreted IgG from day 16 to day 49 (fig. 4A) showed smears of IgG bands, which are characteristic of polyclonal IgG and similar to the IgG IEF pattern of IVIg. All ten experiments (a to j), showed similar patterns of polyclonality indicating that the expanded IgG+ B-lymphocyte population maintained its diversity, even after long-term culture. The presence of EBNA1 was determined only on samples e to j (Fig. 2) and 3 of them (e, f, h) were found positive (data not shown).Validation of Expansion of Switched-memory B LymphocytesThe ability of switched-memory B lymphocytes to expand in larger culture volumes was assessed by serial passaging of three long-term cultures from 6-wells plates to petri dishes. A culture period of 35 to 40 days could be easily achieved, and allowed to reach real culture volumes up to 300 to 450 ml. Cellular densities were maintained between 46105 cells/ml and 36106 cells/ml, which added up to more than 109 total switched-memory B lymphocytes at the end of the culture experiment (Fig. 5 A and B). The three independent samples presented in Figure 5 (k, l and m) expanded in larger volumes, showed expansion rates similar to those Title Loaded From File observed above (Fig. 1) and to experiments done with the same samples cultured in 6-well plates (data not shown). The presence of EBNA1 was detected in expanded cells originated from sample l, whereas those generated with samples k and m were found negative (data not shown). In these experiments, the cumulated supernatants were separately pooled and the total secretion of IgG, IgA, and IgM ranged from 30 to 116 mg/mL, 8 to 49 mg/mL and 1 to 3700 ng/mL, respectively (Fig. 5C). As above, IgM concentration represented less than 4 while IgG consisted of 67 to 93 of total Ig secretion. IEF analysis of these cumulated supernatants, separately and as a pool, also showed a polyclonal IgG distribution (Fig. 4B), which was similar to that of IVIg as well as IgG present in human serum. Flow cytometry analysis of the expanded cells showed acceptable proportions of kappa and lambda light chain (Fig. 12926553 5D) [27] and, as above, all four gamma isotypes were present with Title Loaded From File frequencies declining fro.Ng these experiments. The Tgen period calculated between days 28 to 36 in all these cultures, corresponded to a mean of 51 h69 h (data not shown). Cell viability was also comparable from one cultured sample to another and maintained at an acceptable level, ranging from 93 to 80 at the end of the culture period (Figs. 2C and D). Overall, these culture conditions allowed a final expansion factor, based on the expansion rate and seeding cell numbers, ranging from 107 to 109 after 50 to 65 days.the secretion rate mean values for the ten experiments (Fig. 3D), the relative proportions of IgG1 (67 ), IgG2 (24 ), IgG3 (6 ) and IgG4 (3 ) were comparable to those reported in human serum, namely IgG1 60 615 , IgG2 30 65 , IgG3 7 62 and IgG4 3 61 [25,26]. The IgG total secretion recorded for each culture experiments ranged from 30 to 115 mg/mL (data not shown). Overall these data showed that long-term culture of IgG+ human B lymphocytes did not induce a bias in the secretion of IgG isotypes, which was consistent with the reported proportions in human blood.Expanded IgG+ B Lymphocytes are Polyclonal PopulationsThe degree of heterogeneity of secreted IgG molecules was assessed during the long-term culture by sampling culture supernatant at various time points and analyzing their patterns by isoelectrofocusing. Analysis of secreted IgG from day 16 to day 49 (fig. 4A) showed smears of IgG bands, which are characteristic of polyclonal IgG and similar to the IgG IEF pattern of IVIg. All ten experiments (a to j), showed similar patterns of polyclonality indicating that the expanded IgG+ B-lymphocyte population maintained its diversity, even after long-term culture. The presence of EBNA1 was determined only on samples e to j (Fig. 2) and 3 of them (e, f, h) were found positive (data not shown).Validation of Expansion of Switched-memory B LymphocytesThe ability of switched-memory B lymphocytes to expand in larger culture volumes was assessed by serial passaging of three long-term cultures from 6-wells plates to petri dishes. A culture period of 35 to 40 days could be easily achieved, and allowed to reach real culture volumes up to 300 to 450 ml. Cellular densities were maintained between 46105 cells/ml and 36106 cells/ml, which added up to more than 109 total switched-memory B lymphocytes at the end of the culture experiment (Fig. 5 A and B). The three independent samples presented in Figure 5 (k, l and m) expanded in larger volumes, showed expansion rates similar to those observed above (Fig. 1) and to experiments done with the same samples cultured in 6-well plates (data not shown). The presence of EBNA1 was detected in expanded cells originated from sample l, whereas those generated with samples k and m were found negative (data not shown). In these experiments, the cumulated supernatants were separately pooled and the total secretion of IgG, IgA, and IgM ranged from 30 to 116 mg/mL, 8 to 49 mg/mL and 1 to 3700 ng/mL, respectively (Fig. 5C). As above, IgM concentration represented less than 4 while IgG consisted of 67 to 93 of total Ig secretion. IEF analysis of these cumulated supernatants, separately and as a pool, also showed a polyclonal IgG distribution (Fig. 4B), which was similar to that of IVIg as well as IgG present in human serum. Flow cytometry analysis of the expanded cells showed acceptable proportions of kappa and lambda light chain (Fig. 12926553 5D) [27] and, as above, all four gamma isotypes were present with frequencies declining fro.
