title: T cell dependent differentiation of human B cells: direct switch from IgM to IgE, and sequential switch from IgM via IgG to IgA production.
abstract: Ig production by splenic human B cells that express different surface Ig isotypes were analysed in limiting dilution cultures. Therefore, FACS sorted IgM+, IgG+ and IgA1+ B cells were stimulated with PMA-activated EL4 thymoma cells as helper cells in the presence of IL-2 and IL-4. We found that at least every second B cell responded in vitro and secreted the antibody corresponding to its surface Ig isotype. IgE secreting cells developed from surface IgM+ D+ cells (1/31 to 1/167), but not from IgG+ or IgA1+ cells (much less than 1/5000). Negative signalling of the IgM+ B cells by addition of anti-IgM antibodies into the cultures reduced the number of single IgM producing cells by greater than 85%, and completely inhibited IgE switch. In contrast, anti-IgG and anti-IgA antibodies did not reduce the IgE response. The results indicate a direct switch from IgM to IgE secretion in vitro. In contrast to IgE, IgA secreting cells developed from IgM+D+ (1/30 to 1/51) and from IgG+ B cells (1/14 to 1/25). Negative signalling of the IgG+ B cell subset within total B cells by anti-IgG antibodies suppressed the development of IgG as well as IgA producing cells, but did not inhibit IgM and IgE responses. This indicates a sequential switch from IgM via IgG to IgA. Taken together, this study indicates that IgE secreting cells are derived directly from IgM+D+ B cells by non-sequential switching, whereas IgA producing cells preferentially develop by sequential switching via IgG+ B cells.
authors.affiliation: Ciba-Geigy Ltd, Pharmaceuticals Research Division, Allergy/Immunology, Basel, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Brinkmann
authors.forename: S
authors.initials: S
authors.lastname: Müller
authors.forename: C H
authors.initials: CH
authors.lastname: Heusser
mesh_terms: D000918:Antibody Specificity; D016175:B-Lymphocyte Subsets / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007070:Immunoglobulin A / Q000096:biosynthesis; D007073:Immunoglobulin E / Q000096:biosynthesis; D007074:Immunoglobulin G / Q000096:biosynthesis; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis*; D007075:Immunoglobulin M / Q000096:biosynthesis; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000276:immunology* / Q000502:physiology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M; D007073:Immunoglobulin E