title: Terminal maturation of resting B cells induced by macrophage factors.
abstract: Mouse splenic macrophages from BALB/c nude mice (purified by plastic adherence) or cloned macrophage hybridomas stimulated with jacalin (12.5 micrograms/ml), a D-Gal binding lectin, produce one or more B-cell stimulatory factors which cause splenic B cells from BALB/c or C3H/HeJ mice to secrete immunoglobulin in a polyclonal manner as detected by reverse protein A plaque assays. Jacalin-stimulated macrophage supernatants (JacSup) activate both normal and Percoll gradient-purified small high-density (resting) B cells. Supernatants from total or resting BALB/c spleen cells cultured for 7 days in the presence of JacSup (derived from splenic BALB/c nude mice macrophages) were assayed for immunoglobulin isotypes by ELISA. Resting B cells produce only IgG3 and IgM, whereas total B cells secrete IgG3 and IgM as well as IgG1, IgG2a, IgG2b and IgA. Resting and total B cells from BALB/c nude mice are also stimulated by macrophage supernatants to secrete immunoglobulin, thus indicating that this activity is likely to be T cell independent. Moreover, jacalin-stimulated macrophage supernatants did not induce spleen cells or purified B cells to proliferate. Fractionation of factor-rich supernatants on a Sephacryl S-200 column revealed that the factor activity is located in fractions corresponding to a molecular mass of 25-27 kDa. Taken together, these results suggest that upon the action of a macrophage factor(s) resting B cells undergo terminal differentiation without proliferation in the absence of T cells.
authors.affiliation: Departamento de Immunologia, Cidade Universitária, São Paulo, Brasil.
authors.forename: J
authors.initials: J
authors.lastname: Mengel
authors.forename: A
authors.initials: A
authors.lastname: Campos-Neto
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D018929:Cell Culture Techniques; D037102:Lectins / Q000494:pharmacology*; D008262:Macrophage Activation / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D037121:Plant Lectins; D013154:Spleen / Q000166:cytology
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D037102:Lectins; D037121:Plant Lectins; C043696:jacalin