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Severe attenuation of the B cell immune response in Msh2-deficient mice.

Vora KA, Tumas-Brundage KM, Lentz VM, Cranston A, Fishel R, Manser T - J. Exp. Med. (1999)

Bottom Line: Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation.These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses.Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology and The Kimmel Cancer Institute, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.

ABSTRACT
Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation. Here we show that mice that do not express the MMR factor Msh2 have wide-ranging defects in antigen-driven B cell responses. These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses. Mice heterozygous for the Msh2 deficiency display an "intermediate" phenotype in these regards, suggesting that normal levels of Msh2 expression are critical for the B cell response. Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.

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In vitro proliferative responses  of Msh2-deficient B cells. Small dense  splenic B cells were purified from pools of  cells derived from three mice of each genotype, as described in Materials and Methods,  and cultured for 45–50 h with the indicated  concentrations of LPS, a polyclonal goat  anti–mouse IgM F(ab′)2 preparation, or the  mitogenic anti–mouse CD40 mAb FGK45.  Cell proliferation was then evaluated via a  12–16-h pulse of [3H]thymidine, also as described in Materials and Methods. All culture conditions were performed in triplicate, and error bars are shown. The data  shown are representative of the results of  three independent experiments.
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Figure 6: In vitro proliferative responses of Msh2-deficient B cells. Small dense splenic B cells were purified from pools of cells derived from three mice of each genotype, as described in Materials and Methods, and cultured for 45–50 h with the indicated concentrations of LPS, a polyclonal goat anti–mouse IgM F(ab′)2 preparation, or the mitogenic anti–mouse CD40 mAb FGK45. Cell proliferation was then evaluated via a 12–16-h pulse of [3H]thymidine, also as described in Materials and Methods. All culture conditions were performed in triplicate, and error bars are shown. The data shown are representative of the results of three independent experiments.

Mentions: The lack of evidence for defects in T cell function and mature peripheral B cell numbers and maturity in Msh2 mice prompted a detailed analysis of B cell responses in vitro. Small dense B cells were purified from Msh2 +/+, +/−, and −/− mice and stimulated with anti-IgM F(ab′)2 fragments, LPS, or a mitogenic anti-CD40 mAb in vitro. The cultures were then evaluated for cell cycle progression via [3H]thymidine incorporation. Cell cycle progression and apoptosis were also evaluated using PI–flow cytometric DNA content analysis. Msh2 −/− B cells displayed only slightly reduced proliferation that was not statistically significant compared with +/+ B cells, except at the highest concentrations of stimulant (Fig. 6). PI cell cycle analysis revealed only minor differences in cell cycle progression and apoptosis induced by these same stimuli among the various types of B cells during a 4-d culture period. Msh2 −/− cultures contained only slightly elevated levels of apoptotic cells at early time points in a few experiments (data not shown).


Severe attenuation of the B cell immune response in Msh2-deficient mice.

Vora KA, Tumas-Brundage KM, Lentz VM, Cranston A, Fishel R, Manser T - J. Exp. Med. (1999)

In vitro proliferative responses  of Msh2-deficient B cells. Small dense  splenic B cells were purified from pools of  cells derived from three mice of each genotype, as described in Materials and Methods,  and cultured for 45–50 h with the indicated  concentrations of LPS, a polyclonal goat  anti–mouse IgM F(ab′)2 preparation, or the  mitogenic anti–mouse CD40 mAb FGK45.  Cell proliferation was then evaluated via a  12–16-h pulse of [3H]thymidine, also as described in Materials and Methods. All culture conditions were performed in triplicate, and error bars are shown. The data  shown are representative of the results of  three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2192912&req=5

Figure 6: In vitro proliferative responses of Msh2-deficient B cells. Small dense splenic B cells were purified from pools of cells derived from three mice of each genotype, as described in Materials and Methods, and cultured for 45–50 h with the indicated concentrations of LPS, a polyclonal goat anti–mouse IgM F(ab′)2 preparation, or the mitogenic anti–mouse CD40 mAb FGK45. Cell proliferation was then evaluated via a 12–16-h pulse of [3H]thymidine, also as described in Materials and Methods. All culture conditions were performed in triplicate, and error bars are shown. The data shown are representative of the results of three independent experiments.
Mentions: The lack of evidence for defects in T cell function and mature peripheral B cell numbers and maturity in Msh2 mice prompted a detailed analysis of B cell responses in vitro. Small dense B cells were purified from Msh2 +/+, +/−, and −/− mice and stimulated with anti-IgM F(ab′)2 fragments, LPS, or a mitogenic anti-CD40 mAb in vitro. The cultures were then evaluated for cell cycle progression via [3H]thymidine incorporation. Cell cycle progression and apoptosis were also evaluated using PI–flow cytometric DNA content analysis. Msh2 −/− B cells displayed only slightly reduced proliferation that was not statistically significant compared with +/+ B cells, except at the highest concentrations of stimulant (Fig. 6). PI cell cycle analysis revealed only minor differences in cell cycle progression and apoptosis induced by these same stimuli among the various types of B cells during a 4-d culture period. Msh2 −/− cultures contained only slightly elevated levels of apoptotic cells at early time points in a few experiments (data not shown).

Bottom Line: Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation.These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses.Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology and The Kimmel Cancer Institute, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.

ABSTRACT
Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation. Here we show that mice that do not express the MMR factor Msh2 have wide-ranging defects in antigen-driven B cell responses. These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses. Mice heterozygous for the Msh2 deficiency display an "intermediate" phenotype in these regards, suggesting that normal levels of Msh2 expression are critical for the B cell response. Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.

Show MeSH
Related in: MedlinePlus