title: Rise in inulin-sensitive B cells during ontogeny can be prematurely stimulated by thymus-dependent and thymus-independent antigens.
abstract: We have shown that the delayed acquisition of competence in expression of an anti-inulin (IN) response by neonatal BALB/c mice is preceded by a natural increase in the frequency of IN-sensitive B cells between 3 to 5 weeks of life. Up until 3 weeks of age, BALB/c mice resemble adult germfree mice in their low frequency of IN-sensitive B cells (1 to 2/10(6) B cells). Thereafter, the population of IN-reactive B cells rises about 10-fold to the young adult level, without deliberate immunization. This naturally expanded population of IN-reactive cells has an isotype profile resembling populations arising after intentional priming with other antigens in that it contained a large proportion of cells which generated clones expressing immunoglobulin G and immunoglobulin A isotypes, often without detectable immunoglobulin M. The late rise in frequency of IN-sensitive precursors could be induced prematurely by deliberate priming at 3 days of age with either the thymus-dependent antigen IN-hemocyanin or the thymus-independent bacterial levan. However, no circulating anti-IN could be detected following this early administration of antigen. Thus, the delayed expression of anti-IN does not reflect an absence of B cells of the appropriate specificity which can be stimulated to divide by antigen but rather other events occurring subsequent to perinatal generation of antigen-sensitive cells. Our observations support a role for the beta2 --> 1 fructosyl group as an environmental determinant which selectively expands out preexisting antigen-sensitive B cells at 3 to 5 weeks of age and these include clonotypes which express the predominant anti-IN idiotypes.
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D002999:Clone Cells / Q000276:immunology; D000939:Epitopes; D005630:Fructans / Q000276:immunology; D005856:Germ-Free Life; D006433:Hemocyanins / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007444:Inulin / Q000276:immunology / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010767:Phosphorylcholine / Q000494:pharmacology; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000941:Antigens; D000939:Epitopes; D005630:Fructans; D007075:Immunoglobulin M; D010767:Phosphorylcholine; D007444:Inulin; D006433:Hemocyanins