Endogenous superantigens shape response to exogenous superantigens

Abstract

Endogenous superantigen-mediated thymic negative selection resulted in a paucity of mature T cells bearing T-cell receptor (TCR) Vbeta8 in the periphery. Consequently, the magnitude of immune response to exogenous superantigen staphylococcal enterotoxin B, which activates TCR Vbeta8(+) T cells, was significantly reduced and conferred protection from superantigen-induced mortality.

FIG. 1.

MHC class II expression and T-cell development in HLA-DR transgenic mice. (A) Splenocytes from age-matched HLA-DR3 (DRB*0301) and HLA-DR2 (DRB*1501) transgenic mice (n ≥ 4 mice/group) expressing common DRA*0103 were stained with L227 (anti-DR antibody) to check expression of transgenic HLA-DR by flow cytometry. Shown are percentages of cells expressing DR. (B) CD4⁺ and CD8⁺ T-cell development in DR3 and DR2 mice (n ≥ 4 mice/group) as determined by flow cytometry. Shown are percentages of cells positive for CD4 or CD8.

FIG. 2.

Thymic selection in HLA-DR transgenic mice. Thymocytes from age-matched HLA-DR3 mice (n ≥ 4 mice/group) expressing both DRα and DRβ chains and HLA-DR2 transgenic mice expressing the DRα chain but expressing or lacking the DRβ chain were analyzed by flow cytometry for CD4 and CD8 coreceptors. Note the significant presence of TCR Vβ8⁺ T cells among the single- positive (SP) subsets in DRβ chain-negative DR2 littermates and the absence of TCR Vβ8⁺ T cells in DRβ chain-positive DR2 littermates, indicating the requirement of functional HLA class II molecules for thymic negative selection. Only CD8 SP cells are analyzed, as CD4 SP cells would be absent in the absence of functional class II molecules.

FIG. 3.

TCR Vβ repertoire in HLA-DR transgenic mice. Splenocytes from age-matched HLA-DR3 and -DR2 transgenic mice (n = 3 to 6 mice/group) were stained for CD4, CD8, and TCR Vβ-specific fluorochrome-conjugated antibodies and analyzed by flow cytometry. Shown are percentages of cells expressing a specific TCR Vβ family within the respective gated population.

FIG. 4.

In vitro T-cell response to SEB. Splenocytes from age-matched HLA-DR3 and -DR2 transgenic mice (n = 3 to 6 mice/group) were cultured in vitro with the indicated concentrations of SEB for 42 h. Cell proliferation was determined by thymidine incorporation assay.

FIG. 5.

TCR Vβ repertoire in superantigen-challenged HLA-DR transgenic mice. Splenocytes from age-matched HLA-DR3 and -DR2 transgenic mice (n = 3 to 10 mice/group) challenged with 10 μg of SEB 3 days earlier were stained for CD4, CD8, and TCR Vβ-specific fluorochrome-conjugated antibodies and analyzed by flow cytometry. Shown are percentages of cells expressing specific a TCR Vβ family within the respective gated population.

FIG. 6.

SEB-induced thymic deletion in HLA-DR transgenic mice. Thymocytes from age-matched HLA-DR3 and -DR2 transgenic mice (n = 3 to 10 mice/group) challenged with 10 μg of SEB 3 days earlier were stained for CD4 as well as CD8 and analyzed by flow cytometry. Shown are the reductions in single-positive (SP) and DP thymocyte subsets.