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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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Levels of apoptotic nuclei in antigen-specific GCs of Msh2-deficient mice. Mice were immunized with NP-CGG, and spleens were  taken at day 8 after immunization, sectioned, and stained with PNA and  NP, all as described in Materials and Methods. Parallel sections were  stained with PNA, and apoptotic nuclei were elaborated by the TUNEL  assay. Apoptotic nuclei were counted in eight randomly chosen NP+ GCs  of small and medium size (see Table I). Each value obtained is indicated by  a circle in the scatter plots, with values obtained two, three, or fours times  indicated by light gray, dark gray, and black filled circles, respectively.  Filled squares indicate mean value of apoptotic nuclei for each experimental category. A Student's t test analysis revealed that the differences in levels  of apoptotic nuclei observed between +/+ and −/− mice in both GC  size categories were statistically significant at the 90% confidence level.
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Figure 1: Levels of apoptotic nuclei in antigen-specific GCs of Msh2-deficient mice. Mice were immunized with NP-CGG, and spleens were taken at day 8 after immunization, sectioned, and stained with PNA and NP, all as described in Materials and Methods. Parallel sections were stained with PNA, and apoptotic nuclei were elaborated by the TUNEL assay. Apoptotic nuclei were counted in eight randomly chosen NP+ GCs of small and medium size (see Table I). Each value obtained is indicated by a circle in the scatter plots, with values obtained two, three, or fours times indicated by light gray, dark gray, and black filled circles, respectively. Filled squares indicate mean value of apoptotic nuclei for each experimental category. A Student's t test analysis revealed that the differences in levels of apoptotic nuclei observed between +/+ and −/− mice in both GC size categories were statistically significant at the 90% confidence level.

Mentions: Evaluation of levels of apoptosis in the GCs of Msh2 +/+, +/−, and −/− mice 8 d after immunization via the TUNEL assay showed significantly higher levels of apoptotic nuclei in the small and medium size antigen-specific GCs of Msh2 −/− mice compared with +/+ mice, with +/− mice displaying intermediate levels of such nuclei (Fig. 1). Interestingly, the variation in number of apoptotic nuclei per GC was much larger in Msh2 −/− compared with +/− and +/+ mice. The reduced number of antigen-specific GCs at day 12 in Msh2 −/− mice precluded obtaining a statistically significant comparison of levels of apoptotic nuclei at this time point.


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)

Levels of apoptotic nuclei in antigen-specific GCs of Msh2-deficient mice. Mice were immunized with NP-CGG, and spleens were  taken at day 8 after immunization, sectioned, and stained with PNA and  NP, all as described in Materials and Methods. Parallel sections were  stained with PNA, and apoptotic nuclei were elaborated by the TUNEL  assay. Apoptotic nuclei were counted in eight randomly chosen NP+ GCs  of small and medium size (see Table I). Each value obtained is indicated by  a circle in the scatter plots, with values obtained two, three, or fours times  indicated by light gray, dark gray, and black filled circles, respectively.  Filled squares indicate mean value of apoptotic nuclei for each experimental category. A Student's t test analysis revealed that the differences in levels  of apoptotic nuclei observed between +/+ and −/− mice in both GC  size categories were statistically significant at the 90% confidence level.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: Levels of apoptotic nuclei in antigen-specific GCs of Msh2-deficient mice. Mice were immunized with NP-CGG, and spleens were taken at day 8 after immunization, sectioned, and stained with PNA and NP, all as described in Materials and Methods. Parallel sections were stained with PNA, and apoptotic nuclei were elaborated by the TUNEL assay. Apoptotic nuclei were counted in eight randomly chosen NP+ GCs of small and medium size (see Table I). Each value obtained is indicated by a circle in the scatter plots, with values obtained two, three, or fours times indicated by light gray, dark gray, and black filled circles, respectively. Filled squares indicate mean value of apoptotic nuclei for each experimental category. A Student's t test analysis revealed that the differences in levels of apoptotic nuclei observed between +/+ and −/− mice in both GC size categories were statistically significant at the 90% confidence level.
Mentions: Evaluation of levels of apoptosis in the GCs of Msh2 +/+, +/−, and −/− mice 8 d after immunization via the TUNEL assay showed significantly higher levels of apoptotic nuclei in the small and medium size antigen-specific GCs of Msh2 −/− mice compared with +/+ mice, with +/− mice displaying intermediate levels of such nuclei (Fig. 1). Interestingly, the variation in number of apoptotic nuclei per GC was much larger in Msh2 −/− compared with +/− and +/+ mice. The reduced number of antigen-specific GCs at day 12 in Msh2 −/− mice precluded obtaining a statistically significant comparison of levels of apoptotic nuclei at this time point.

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