title: Outer periarteriolar lymphoid sheath arrest and subsequent differentiation of both naive and tolerant immunoglobulin transgenic B cells is determined by B cell receptor occupancy.
abstract: T-dependent B cell responses in the spleen are initiated in the outer periarteriolar lymphoid sheath (PALS) and culminate in the generation of proliferative foci and germinal center reactions. By pulsing anti-hen egg lysozyme (HEL) immunoglobulin transgenic (IgTg) B cells with various concentrations of HEL in vitro before adoptive transfer into normal recipients, it was shown that a critical number of B cell receptors (BCRs) must be ligated for B cells to undergo arrest in the outer PALS. T cell help was manipulated independently of the BCR stimulus by incubating B cells expressing the appropriate major histocompatibility complex class II antigen with a peptide recognized by CD4(+) TCR Tg T cells. B cells which either failed to arrest in the outer PALS due to a subthreshold BCR stimulus, or arrested only transiently due to the brevity of the BCR stimulus, underwent an abortive response within the follicles when provided with T cell help. In contrast, naive B cells stimulated by a sustained, suprathreshold concentration of either foreign or self-antigen and given T cell help, proliferated in the outer PALS and then differentiated. Outer PALS arrest was not influenced by the nature of the B cells occupying the follicle, but appeared to be determined solely by the magnitude of BCR stimulation. Thus antigen-pulsed B cells arrested in the outer PALS in an identical manner irrespective of whether the follicles comprised a population of normal B cells with multiple specificities, a monoclonal naive population, or a monoclonal population of tolerant B cells. In addition, tolerant B cells were found to relocate from the follicles to the outer PALS of HEL/anti-HEL double Tg mice in which the concentration of soluble self-antigen had been increased by zinc feeding. Similarly, when anti-HEL Tg mice were crossed with a second HEL Tg strain expressing a higher concentration of soluble HEL, the tolerant anti-HEL Tg B cells were located constitutively in the outer PALS. Thus, subtle variations in antigen concentration resulted in dramatic changes in positioning of B cells within the spleen. A series of mixed bone marrow chimeras in which the effective antigen concentration was inversely related to the number of self-reactive B cells due to absorption of antigen by transgene-encoded membrane and secreted Ig, was used to confirm that alteration in B cell position previously attributed to changes in follicular composition could be explained on the basis of available antigen concentration, rather than the diversity of the repertoire.
authors.affiliation: Centenary Institute for Cancer Medicine and Cell Biology, Newtown, Sydney, New South Wales, Australia 2042.
authors.forename: M C
authors.initials: MC
authors.lastname: Cook
authors.forename: A
authors.initials: A
authors.lastname: Basten
authors.forename: B
authors.initials: B
authors.lastname: Fazekas de St Groth
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002678:Chimera; D017637:Clonal Deletion; D015536:Down-Regulation; D005260:Female; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009113:Muramidase / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000502:physiology*; D017634:Self Tolerance; D013154:Spleen / Q000166:cytology / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors
chemical_list: D011947:Receptors, Antigen, B-Cell; D009113:Muramidase