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The CD8 population in CD4-deficient mice is heavily contaminated with MHC class II-restricted T cells.

Tyznik AJ, Sun JC, Bevan MJ - J. Exp. Med. (2004)

Bottom Line: In experiments to study the impact of deficiency in CD4+ T cell help on the magnitude of CD8+ cytotoxic T cell response to pathogens, it was noted that in CD4 gene knockout mice, the CD8 population made significant responses to several nominally major histocompatibility complex (MHC) class II-restricted epitopes in addition to the expected responses to MHC class I-restricted epitopes.Further experiments suggested that these two observations are linked and that the CD8 population in CD4-/- mice may contain a majority of T cells that were actually selected by recognition of MHC class II molecules in the thymus.These results have implications for understanding CD4 versus CD8 lineage commitment in the thymus, and for the practical use of CD4-/- mice as models of helper deficiency.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, University of Washington, Seattle 98195, USA.

ABSTRACT
In experiments to study the impact of deficiency in CD4+ T cell help on the magnitude of CD8+ cytotoxic T cell response to pathogens, it was noted that in CD4 gene knockout mice, the CD8 population made significant responses to several nominally major histocompatibility complex (MHC) class II-restricted epitopes in addition to the expected responses to MHC class I-restricted epitopes. A similar response by CD8+ T cells to class II-restricted epitopes was not observed in wild-type mice, or in mice that had been acutely depleted of CD4+ T cells just before the immunization. Coincident with this unexpected response to class II-restricted epitopes, it was also observed that the CD8+ response to the class I-restricted epitopes was consistently lower in CD4-/- mice than in wild-type mice. Further experiments suggested that these two observations are linked and that the CD8 population in CD4-/- mice may contain a majority of T cells that were actually selected by recognition of MHC class II molecules in the thymus. These results have implications for understanding CD4 versus CD8 lineage commitment in the thymus, and for the practical use of CD4-/- mice as models of helper deficiency.

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Primary response of wild-type and CD4−/− mice to MHC class I and class II–restricted peptides after rLmOva infection. 7 d after infection, splenocytes were stimulated in vitro with LLO190–201, Ova257–264, or no peptide and stained for levels of intracellular IFN-γ. (A) Response of CD4+ T cells to peptides. (B) Response of CD8+ T cells to peptides. Numbers indicate the percentage of IFN-γ–positive cells in the CD4+ or CD8+ population. There were 2.3 × 106 Ova257–264-specific CD8+ T cells in wild-type spleen and 106 in CD4−/− spleen. (C) Lysis of 51Cr-labeled control, Ova257–264, or LLO190–201-coated LB27.4 targets by spleen cells from wild-type (squares) and CD4−/− mice (diamonds) assayed directly ex vivo. These data are representative of four independent experiments of two mice per group. (D) Response of CD8+ T cells to Ova257–264 in wild-type and CD4−/− mice. Data represent the average of eight mice per group.
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fig1: Primary response of wild-type and CD4−/− mice to MHC class I and class II–restricted peptides after rLmOva infection. 7 d after infection, splenocytes were stimulated in vitro with LLO190–201, Ova257–264, or no peptide and stained for levels of intracellular IFN-γ. (A) Response of CD4+ T cells to peptides. (B) Response of CD8+ T cells to peptides. Numbers indicate the percentage of IFN-γ–positive cells in the CD4+ or CD8+ population. There were 2.3 × 106 Ova257–264-specific CD8+ T cells in wild-type spleen and 106 in CD4−/− spleen. (C) Lysis of 51Cr-labeled control, Ova257–264, or LLO190–201-coated LB27.4 targets by spleen cells from wild-type (squares) and CD4−/− mice (diamonds) assayed directly ex vivo. These data are representative of four independent experiments of two mice per group. (D) Response of CD8+ T cells to Ova257–264 in wild-type and CD4−/− mice. Data represent the average of eight mice per group.

Mentions: To investigate the role of CD4 T cells in protection against an intracellular bacterium, we analyzed T cell responses to L. monocytogenes in wild-type and CD4−/− mice. Because naturally derived H2b class I–restricted peptides from L. monocytogenes have not been identified, we took advantage of a recombinant form, rLmOva, that expresses the H-2Kb–restricted epitope, Ova257–264, as well as the endogenous I-Ab–restricted CD4 epitope, LLO190–201. Wild-type and CD4−/− mice were infected with a sublethal dose of rLmOva and T cell responses were assessed by intracellular IFN-γ staining and 51Cr release assays 7 d after infection. Wild-type mice responded as expected with strong CD4+ T cell responses to LLO190–201 and strong CD8+ T cell responses to Ova257–264 (Fig. 1, A and B). Surprisingly, the CD8+ T cell population in the CD4−/− mice showed good IFN-γ responses to both the class II–restricted LLO190–201 and class I–restricted Ova257–264 peptides. This pattern of response was also observed in a 4-h 51Cr release assay. In addition to secreting IFN-γ, the LLO190–201-specific T cells from both types of mice were able to kill targets in a short-term assay (Fig. 1 C). Of note was the fact that the magnitude of the CD8 response to Ova257–264 in CD4−/− mice was approximately half of that in wild type (Fig. 1 B). This was a consistent finding, and a summary of all the comparisons of the CD8 response of wild-type and CD4−/− mice to the Ova257–264 peptide is presented in Fig. 1 D.


The CD8 population in CD4-deficient mice is heavily contaminated with MHC class II-restricted T cells.

Tyznik AJ, Sun JC, Bevan MJ - J. Exp. Med. (2004)

Primary response of wild-type and CD4−/− mice to MHC class I and class II–restricted peptides after rLmOva infection. 7 d after infection, splenocytes were stimulated in vitro with LLO190–201, Ova257–264, or no peptide and stained for levels of intracellular IFN-γ. (A) Response of CD4+ T cells to peptides. (B) Response of CD8+ T cells to peptides. Numbers indicate the percentage of IFN-γ–positive cells in the CD4+ or CD8+ population. There were 2.3 × 106 Ova257–264-specific CD8+ T cells in wild-type spleen and 106 in CD4−/− spleen. (C) Lysis of 51Cr-labeled control, Ova257–264, or LLO190–201-coated LB27.4 targets by spleen cells from wild-type (squares) and CD4−/− mice (diamonds) assayed directly ex vivo. These data are representative of four independent experiments of two mice per group. (D) Response of CD8+ T cells to Ova257–264 in wild-type and CD4−/− mice. Data represent the average of eight mice per group.
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Related In: Results  -  Collection

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fig1: Primary response of wild-type and CD4−/− mice to MHC class I and class II–restricted peptides after rLmOva infection. 7 d after infection, splenocytes were stimulated in vitro with LLO190–201, Ova257–264, or no peptide and stained for levels of intracellular IFN-γ. (A) Response of CD4+ T cells to peptides. (B) Response of CD8+ T cells to peptides. Numbers indicate the percentage of IFN-γ–positive cells in the CD4+ or CD8+ population. There were 2.3 × 106 Ova257–264-specific CD8+ T cells in wild-type spleen and 106 in CD4−/− spleen. (C) Lysis of 51Cr-labeled control, Ova257–264, or LLO190–201-coated LB27.4 targets by spleen cells from wild-type (squares) and CD4−/− mice (diamonds) assayed directly ex vivo. These data are representative of four independent experiments of two mice per group. (D) Response of CD8+ T cells to Ova257–264 in wild-type and CD4−/− mice. Data represent the average of eight mice per group.
Mentions: To investigate the role of CD4 T cells in protection against an intracellular bacterium, we analyzed T cell responses to L. monocytogenes in wild-type and CD4−/− mice. Because naturally derived H2b class I–restricted peptides from L. monocytogenes have not been identified, we took advantage of a recombinant form, rLmOva, that expresses the H-2Kb–restricted epitope, Ova257–264, as well as the endogenous I-Ab–restricted CD4 epitope, LLO190–201. Wild-type and CD4−/− mice were infected with a sublethal dose of rLmOva and T cell responses were assessed by intracellular IFN-γ staining and 51Cr release assays 7 d after infection. Wild-type mice responded as expected with strong CD4+ T cell responses to LLO190–201 and strong CD8+ T cell responses to Ova257–264 (Fig. 1, A and B). Surprisingly, the CD8+ T cell population in the CD4−/− mice showed good IFN-γ responses to both the class II–restricted LLO190–201 and class I–restricted Ova257–264 peptides. This pattern of response was also observed in a 4-h 51Cr release assay. In addition to secreting IFN-γ, the LLO190–201-specific T cells from both types of mice were able to kill targets in a short-term assay (Fig. 1 C). Of note was the fact that the magnitude of the CD8 response to Ova257–264 in CD4−/− mice was approximately half of that in wild type (Fig. 1 B). This was a consistent finding, and a summary of all the comparisons of the CD8 response of wild-type and CD4−/− mice to the Ova257–264 peptide is presented in Fig. 1 D.

Bottom Line: In experiments to study the impact of deficiency in CD4+ T cell help on the magnitude of CD8+ cytotoxic T cell response to pathogens, it was noted that in CD4 gene knockout mice, the CD8 population made significant responses to several nominally major histocompatibility complex (MHC) class II-restricted epitopes in addition to the expected responses to MHC class I-restricted epitopes.Further experiments suggested that these two observations are linked and that the CD8 population in CD4-/- mice may contain a majority of T cells that were actually selected by recognition of MHC class II molecules in the thymus.These results have implications for understanding CD4 versus CD8 lineage commitment in the thymus, and for the practical use of CD4-/- mice as models of helper deficiency.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, University of Washington, Seattle 98195, USA.

ABSTRACT
In experiments to study the impact of deficiency in CD4+ T cell help on the magnitude of CD8+ cytotoxic T cell response to pathogens, it was noted that in CD4 gene knockout mice, the CD8 population made significant responses to several nominally major histocompatibility complex (MHC) class II-restricted epitopes in addition to the expected responses to MHC class I-restricted epitopes. A similar response by CD8+ T cells to class II-restricted epitopes was not observed in wild-type mice, or in mice that had been acutely depleted of CD4+ T cells just before the immunization. Coincident with this unexpected response to class II-restricted epitopes, it was also observed that the CD8+ response to the class I-restricted epitopes was consistently lower in CD4-/- mice than in wild-type mice. Further experiments suggested that these two observations are linked and that the CD8 population in CD4-/- mice may contain a majority of T cells that were actually selected by recognition of MHC class II molecules in the thymus. These results have implications for understanding CD4 versus CD8 lineage commitment in the thymus, and for the practical use of CD4-/- mice as models of helper deficiency.

Show MeSH
Related in: MedlinePlus