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Activation of virus-specific memory B cells in the absence of T cell help.

Hebeis BJ, Klenovsek K, Rohwer P, Ritter U, Schneider A, Mach M, Winkler TH - J. Exp. Med. (2004)

Bottom Line: Antigenic stimulation 4-6 d after transfer of B cells resulted in rapid IgG production.Transfer of memory B cells into immunocompetent animals indicated that presence of helper T cells did not enhance the memory B cell response.Therefore, our results indicate that activation of virus-specific memory B cells to secrete IgG is independent of cognate or bystander T cell help.

View Article: PubMed Central - PubMed

Affiliation: Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, D-91054 Erlangen, Germany.

ABSTRACT
Humoral immunity is maintained by long-lived plasma cells, constitutively secreting antibodies, and nonsecreting resting memory B cells that are rapidly reactivated upon antigen encounter. The activation requirements for resting memory B cells, particularly the role of T helper cells, are unclear. To analyze the activation of memory B cells, mice were immunized with human cytomegalovirus, a complex human herpesvirus, and tick-born encephalitis virus, and a simple flavivirus. B cell populations devoid of Ig-secreting plasma cells were adoptively transferred into T and B cell-deficient RAG-1-/- mice. Antigenic stimulation 4-6 d after transfer of B cells resulted in rapid IgG production. The response was long lasting and strictly antigen specific, excluding polyclonal B cell activation. CD4+ T cells were not involved since (a) further depletion of CD4+ T cells in the recipient mice did not alter the antibody response and (b) recipient mice contained no detectable CD4+ T cells 90 d posttransfer. Memory B cells could not be activated by a soluble viral protein without T cell help. Transfer of memory B cells into immunocompetent animals indicated that presence of helper T cells did not enhance the memory B cell response. Therefore, our results indicate that activation of virus-specific memory B cells to secrete IgG is independent of cognate or bystander T cell help.

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T cell depletion and T cell numbers in recipient mice. (A) RAG-1−/− mice adoptively transferred with immune B cells were injected with 500 μg GK1.5 antibody 2 d before and on the day of stimulation with 10 μg HCMV-DBs. Blood was taken on the days indicated, and sera were analyzed for HCMV-specific IgG (♦) compared with sera of untreated recipients (▪). (B) Spleens and blood were taken from RAG-1−/− mice, RAG-1−/− mice 90 d post adoptive transfer and from donor mice. Single cell suspensions were stained with FITC- or PE-conjugated antibodies and analyzed by FACScan. The specificities of the staining antibodies are indicated at the axes.
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fig3: T cell depletion and T cell numbers in recipient mice. (A) RAG-1−/− mice adoptively transferred with immune B cells were injected with 500 μg GK1.5 antibody 2 d before and on the day of stimulation with 10 μg HCMV-DBs. Blood was taken on the days indicated, and sera were analyzed for HCMV-specific IgG (♦) compared with sera of untreated recipients (▪). (B) Spleens and blood were taken from RAG-1−/− mice, RAG-1−/− mice 90 d post adoptive transfer and from donor mice. Single cell suspensions were stained with FITC- or PE-conjugated antibodies and analyzed by FACScan. The specificities of the staining antibodies are indicated at the axes.

Mentions: Although the purity of our B cell preparations argued against a participation of CD4+ T cells in the observed memory response, we further investigated a potential involvement of small numbers of CD4+ T cells in this process. First, potentially contaminating CD4+ T cells were depleted in recipient RAG-1−/− mice after transfer and before challenge. To this end, recipient mice were treated with depleting CD4-specific antibody GK1.5. The antibody concentration used was sufficient for a complete abrogation of a primary antibody response to HCMV-DBs in C57BL/6 mice (Fig. 2). When HCMV-DB–specific IgG was measured between days 10 and 60 postchallenge, no difference in antibody titers was observed between animals that had received GK1.5 and the control mice (Fig. 3 A). Second, spleens and blood of recipient mice were analyzed for the presence of CD4+ T helper cells 90 d after transfer. This time period is expected to be sufficient for homeostatic expansion of potentially contaminating T cells to detectable numbers (16). Neither the spleen nor the blood of recipient RAG-1−/− mice harbored cells, which were CD4+/TCR+, indicating that the transferred B cell population contained no or negligible numbers of CD4+ and CD8+ or γ/δ-TCR+ T cells (Fig. 3 B).


Activation of virus-specific memory B cells in the absence of T cell help.

Hebeis BJ, Klenovsek K, Rohwer P, Ritter U, Schneider A, Mach M, Winkler TH - J. Exp. Med. (2004)

T cell depletion and T cell numbers in recipient mice. (A) RAG-1−/− mice adoptively transferred with immune B cells were injected with 500 μg GK1.5 antibody 2 d before and on the day of stimulation with 10 μg HCMV-DBs. Blood was taken on the days indicated, and sera were analyzed for HCMV-specific IgG (♦) compared with sera of untreated recipients (▪). (B) Spleens and blood were taken from RAG-1−/− mice, RAG-1−/− mice 90 d post adoptive transfer and from donor mice. Single cell suspensions were stained with FITC- or PE-conjugated antibodies and analyzed by FACScan. The specificities of the staining antibodies are indicated at the axes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211828&req=5

fig3: T cell depletion and T cell numbers in recipient mice. (A) RAG-1−/− mice adoptively transferred with immune B cells were injected with 500 μg GK1.5 antibody 2 d before and on the day of stimulation with 10 μg HCMV-DBs. Blood was taken on the days indicated, and sera were analyzed for HCMV-specific IgG (♦) compared with sera of untreated recipients (▪). (B) Spleens and blood were taken from RAG-1−/− mice, RAG-1−/− mice 90 d post adoptive transfer and from donor mice. Single cell suspensions were stained with FITC- or PE-conjugated antibodies and analyzed by FACScan. The specificities of the staining antibodies are indicated at the axes.
Mentions: Although the purity of our B cell preparations argued against a participation of CD4+ T cells in the observed memory response, we further investigated a potential involvement of small numbers of CD4+ T cells in this process. First, potentially contaminating CD4+ T cells were depleted in recipient RAG-1−/− mice after transfer and before challenge. To this end, recipient mice were treated with depleting CD4-specific antibody GK1.5. The antibody concentration used was sufficient for a complete abrogation of a primary antibody response to HCMV-DBs in C57BL/6 mice (Fig. 2). When HCMV-DB–specific IgG was measured between days 10 and 60 postchallenge, no difference in antibody titers was observed between animals that had received GK1.5 and the control mice (Fig. 3 A). Second, spleens and blood of recipient mice were analyzed for the presence of CD4+ T helper cells 90 d after transfer. This time period is expected to be sufficient for homeostatic expansion of potentially contaminating T cells to detectable numbers (16). Neither the spleen nor the blood of recipient RAG-1−/− mice harbored cells, which were CD4+/TCR+, indicating that the transferred B cell population contained no or negligible numbers of CD4+ and CD8+ or γ/δ-TCR+ T cells (Fig. 3 B).

Bottom Line: Antigenic stimulation 4-6 d after transfer of B cells resulted in rapid IgG production.Transfer of memory B cells into immunocompetent animals indicated that presence of helper T cells did not enhance the memory B cell response.Therefore, our results indicate that activation of virus-specific memory B cells to secrete IgG is independent of cognate or bystander T cell help.

View Article: PubMed Central - PubMed

Affiliation: Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, D-91054 Erlangen, Germany.

ABSTRACT
Humoral immunity is maintained by long-lived plasma cells, constitutively secreting antibodies, and nonsecreting resting memory B cells that are rapidly reactivated upon antigen encounter. The activation requirements for resting memory B cells, particularly the role of T helper cells, are unclear. To analyze the activation of memory B cells, mice were immunized with human cytomegalovirus, a complex human herpesvirus, and tick-born encephalitis virus, and a simple flavivirus. B cell populations devoid of Ig-secreting plasma cells were adoptively transferred into T and B cell-deficient RAG-1-/- mice. Antigenic stimulation 4-6 d after transfer of B cells resulted in rapid IgG production. The response was long lasting and strictly antigen specific, excluding polyclonal B cell activation. CD4+ T cells were not involved since (a) further depletion of CD4+ T cells in the recipient mice did not alter the antibody response and (b) recipient mice contained no detectable CD4+ T cells 90 d posttransfer. Memory B cells could not be activated by a soluble viral protein without T cell help. Transfer of memory B cells into immunocompetent animals indicated that presence of helper T cells did not enhance the memory B cell response. Therefore, our results indicate that activation of virus-specific memory B cells to secrete IgG is independent of cognate or bystander T cell help.

Show MeSH
Related in: MedlinePlus