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Germinal center initiation, variable gene region hypermutation, and mutant B cell selection without detectable immune complexes on follicular dendritic cells.

Hannum LG, Haberman AM, Anderson SM, Shlomchik MJ - J. Exp. Med. (2000)

Bottom Line: Among these is to promote the deposition of immune complexes (ICs) on follicular dendritic cells (FDCs).ICs on FDCs are generally thought to be critical for normal germinal center (GC) formation and the development and selection of memory B cells.Moreover, as indicated by the presence and pattern of somatic mutations, memory cell formation and selection appear normal in these IC-deficient GCs.

View Article: PubMed Central - PubMed

Affiliation: Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

ABSTRACT
Serum antibody (Ab) can play several roles during B cell immune responses. Among these is to promote the deposition of immune complexes (ICs) on follicular dendritic cells (FDCs). ICs on FDCs are generally thought to be critical for normal germinal center (GC) formation and the development and selection of memory B cells. However, it has been very difficult to test these ideas. To determine directly whether FDC-bound complexes do indeed function in these roles, we have developed a transgenic (Tg) mouse in which all B lymphocytes produce only the membrane-bound form of immunoglobulin M. Immune Tg mice have 10,000-fold less specific Ab than wild-type mice and lack detectable ICs on FDCs. Nonetheless, primary immune responses and the GC reaction in these mice are robust, suggesting that ICs on FDCs do not play critical roles in immune response initiation and GC formation. Moreover, as indicated by the presence and pattern of somatic mutations, memory cell formation and selection appear normal in these IC-deficient GCs.

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Time course analysis of primary response to NP immunization. mIg and (m+s)Ig Tg splenocytes were analyzed by FACS® at various time points after immunization with NP-HSA, NP-CGG, or CGG alone. (A) Mean percentages of NP-specific splenocytes; (B) the mean percentage of NP-specific splenocytes that are B7-2high. Error bars indicate SEM. Numbers of mice: d0, n = 4; d28, n = 3; d5–16, NP-HSA, n = 3; CGG mIg Tg, n = 4–5; NP-CGG mIg Tg, n = 5–6; CGG (m+s)Ig Tg, n = 3; NP-CGG (m+s)Ig Tg, n = 4–7. Data are combined from three experiments.
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Figure 3: Time course analysis of primary response to NP immunization. mIg and (m+s)Ig Tg splenocytes were analyzed by FACS® at various time points after immunization with NP-HSA, NP-CGG, or CGG alone. (A) Mean percentages of NP-specific splenocytes; (B) the mean percentage of NP-specific splenocytes that are B7-2high. Error bars indicate SEM. Numbers of mice: d0, n = 4; d28, n = 3; d5–16, NP-HSA, n = 3; CGG mIg Tg, n = 4–5; NP-CGG mIg Tg, n = 5–6; CGG (m+s)Ig Tg, n = 3; NP-CGG (m+s)Ig Tg, n = 4–7. Data are combined from three experiments.

Mentions: Having eliminated preexisting Ab, we asked whether mIg Tg mice would develop a normal primary response, since ICs might be important in the initial stimulation of B cells 2728. To determine if primary responses in mice with similar B cell repertoires would be diminished by lack of Ab, mIg Tg and (m+s)Ig Tg mice were immunized with NP-HSA, NP-CGG, or CGG alone, and splenocytes were analyzed by FACS® between days 0 and 28 (Fig. 3). Ag-specific B cells bound NIP-PE and expressed λ light chain (Fig. 1). In NP-immunized mIg Tg and (m+s)Ig Tg mice, Ag-specific B cells comprised an increasingly large percentage of the splenocytes (Fig. 3 A), peaking between days 12 and 16. Similar effects were seen on the total number of NP-specific cells (data not shown). There is a similar proportional increase of NP-specific cells in both strains. By day 28, the percentage of NP-specific cells in both Tg strains had dropped, although not yet back to baseline levels. NP-specific B cells in carrier-immunized controls remained near baseline levels.


Germinal center initiation, variable gene region hypermutation, and mutant B cell selection without detectable immune complexes on follicular dendritic cells.

Hannum LG, Haberman AM, Anderson SM, Shlomchik MJ - J. Exp. Med. (2000)

Time course analysis of primary response to NP immunization. mIg and (m+s)Ig Tg splenocytes were analyzed by FACS® at various time points after immunization with NP-HSA, NP-CGG, or CGG alone. (A) Mean percentages of NP-specific splenocytes; (B) the mean percentage of NP-specific splenocytes that are B7-2high. Error bars indicate SEM. Numbers of mice: d0, n = 4; d28, n = 3; d5–16, NP-HSA, n = 3; CGG mIg Tg, n = 4–5; NP-CGG mIg Tg, n = 5–6; CGG (m+s)Ig Tg, n = 3; NP-CGG (m+s)Ig Tg, n = 4–7. Data are combined from three experiments.
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Related In: Results  -  Collection

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Figure 3: Time course analysis of primary response to NP immunization. mIg and (m+s)Ig Tg splenocytes were analyzed by FACS® at various time points after immunization with NP-HSA, NP-CGG, or CGG alone. (A) Mean percentages of NP-specific splenocytes; (B) the mean percentage of NP-specific splenocytes that are B7-2high. Error bars indicate SEM. Numbers of mice: d0, n = 4; d28, n = 3; d5–16, NP-HSA, n = 3; CGG mIg Tg, n = 4–5; NP-CGG mIg Tg, n = 5–6; CGG (m+s)Ig Tg, n = 3; NP-CGG (m+s)Ig Tg, n = 4–7. Data are combined from three experiments.
Mentions: Having eliminated preexisting Ab, we asked whether mIg Tg mice would develop a normal primary response, since ICs might be important in the initial stimulation of B cells 2728. To determine if primary responses in mice with similar B cell repertoires would be diminished by lack of Ab, mIg Tg and (m+s)Ig Tg mice were immunized with NP-HSA, NP-CGG, or CGG alone, and splenocytes were analyzed by FACS® between days 0 and 28 (Fig. 3). Ag-specific B cells bound NIP-PE and expressed λ light chain (Fig. 1). In NP-immunized mIg Tg and (m+s)Ig Tg mice, Ag-specific B cells comprised an increasingly large percentage of the splenocytes (Fig. 3 A), peaking between days 12 and 16. Similar effects were seen on the total number of NP-specific cells (data not shown). There is a similar proportional increase of NP-specific cells in both strains. By day 28, the percentage of NP-specific cells in both Tg strains had dropped, although not yet back to baseline levels. NP-specific B cells in carrier-immunized controls remained near baseline levels.

Bottom Line: Among these is to promote the deposition of immune complexes (ICs) on follicular dendritic cells (FDCs).ICs on FDCs are generally thought to be critical for normal germinal center (GC) formation and the development and selection of memory B cells.Moreover, as indicated by the presence and pattern of somatic mutations, memory cell formation and selection appear normal in these IC-deficient GCs.

View Article: PubMed Central - PubMed

Affiliation: Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

ABSTRACT
Serum antibody (Ab) can play several roles during B cell immune responses. Among these is to promote the deposition of immune complexes (ICs) on follicular dendritic cells (FDCs). ICs on FDCs are generally thought to be critical for normal germinal center (GC) formation and the development and selection of memory B cells. However, it has been very difficult to test these ideas. To determine directly whether FDC-bound complexes do indeed function in these roles, we have developed a transgenic (Tg) mouse in which all B lymphocytes produce only the membrane-bound form of immunoglobulin M. Immune Tg mice have 10,000-fold less specific Ab than wild-type mice and lack detectable ICs on FDCs. Nonetheless, primary immune responses and the GC reaction in these mice are robust, suggesting that ICs on FDCs do not play critical roles in immune response initiation and GC formation. Moreover, as indicated by the presence and pattern of somatic mutations, memory cell formation and selection appear normal in these IC-deficient GCs.

Show MeSH
Related in: MedlinePlus