Beta interferon is produced by Chlamydia trachomatis-infected fibroblast-like synoviocytes and inhibits gamma interferon-induced HLA-DR expression

Abstract

Infection of fibroblast-like synovial cells with Chlamydia trachomatis (serotype D strain IC Cal 8) in culture induced the secretion of beta interferon (IFN-beta). Chlamydial infection inhibited IFN-gamma-induced expression of HLA-DR antigen in the cells. Addition of IFN-beta antibody directly to infected cultures mitigated HLA-DR inhibition, suggesting involvement of produced IFN-beta.

FIG. 1

Effect of IFN-β on chlamydial yield in SC. Values are the means and standard deviations of three different experiments.

FIG. 2

Expression of HLA-DR molecules in C. trachomatis-infected cultures of SC detected by immunofluorescence staining. (A) Incubation with 10 U of IFN-γ per ml for 48 h induces HLA-DR molecules as indicated by the granular staining of SC. Cells were stained for HLA-DR by indirect immunofluorescence with an RPE-conjugated secondary antibody. Magnification, ca. ×200. (B) Following chlamydial infection and incubation with IFN-γ, a smaller number of SC show positive staining for HLA-DR antigen. Chlamydial inclusions were stained with FITC-conjugated antibody to MOMP. Magnification, ca. ×200.

FIG. 3

Reduction of IFN-γ-induced HLA-DR expression on synovial fibroblasts after infection with C. trachomatis. (A) Mock-infected cells incubated in culture medium without IFN-γ (0.4% positive cells; total mean fluorescence intensity [MFI] = 97). (B) Mock-infected cells stimulated with 10 U of IFN-γ per ml (92% positive cells; MFI = 4,190). (C) Chlamydia-infected cells (MOI of 5) stimulated with 10 U of IFN-γ per ml (59% positive cells; MFI = 1,658). (D) Chlamydia-infected cells (MOI of 5) treated with IFN-γ (10 U/ml) and IFN-β antibody (100 nU/ml) (77% positive cells; MFI = 2,366). (E) Chlamydia-infected cells (MOI of 10) stimulated with 10 U of IFN-γ per ml (28% positive cells; MFI = 830). (F) Chlamydia-infected cells (MOI of 10) treated with IFN-γ (10 U/ml) and IFN-β antibody (100 nU/ml) (68% positive cells; MFI = 2,026). Flow cytometric analysis was performed after 48 h of incubation of cell cultures.