Chlamydia pneumoniae-Induced IFN-Gamma Responses in Peripheral Blood Mononuclear Cells Increase Numbers of CD4+ but Not CD8+ T Effector Memory Cells

Abstract

Background Chlamydia pneumoniae causes respiratory infection in adults and children. Previous studies in our laboratory identified significantly higher in vitro T lymphocyte responses to C. pneumoniae in children with asthma compared to healthy controls which may indicate the presence of T effector memory (TEM) lymphocytes. Aim In the present study, healthy subjects were screened for the presence of TEM cells and their cytokines. CCR7 negative effector TEMs may indicate persistent infection with C. pneumoniae . Methods Peripheral blood mononuclear cells (PBMC) (1×10 6 /mL) from adult non-asthmatic subjects were infected for 1h ± C. pneumoniae TW-183 at a multiplicity of infection (MOI) = 0.1 and cultured (48 hrs). Distributions of lymphocytes (CD4+, CD8+) and TEM cells (CD4+CCR7+CD45RA+CD154+, CD8+CCR7+CD45RA+CD154+) were determined. Levels of intracellular interleukin (IL)-2, IL-4, and interferon (IFN)-gamma were measured (flow microfluorimetry); IFN-gamma was measured in supernatants (ELISA). Results C. pneumoniae infection led to a decrease in numbers of CD8+ TEM and CD8+CD154+ cells; CD4+TEM and CD4+CD154+ cells did not change. Numbers of TEM cells (CD4+IL-2+, CD8+ IL-2+) also decreased. However, number of TEM cells (CD4+IL4-+, CD8+ IL-4+) and (CD4+ IFN-gamma+, CD8+IFN-gamma+) did not change. When stratified according to IFN-gamma+ status, numbers of CD4+ IL-2+ and CD4+IL-4+ TEMs increased; CD8+IL-2+ and CD8+ IL-4+ TEMs decreased. Conclusion C. pneumoniae -induced PBMC IFN-gamma+ responses increased numbers of CD4+ IL-2+ and CD4+IL-4+ TEM cells, while CD8+IL-2+ and CD8+IL-4+ TEMs decreased. Production of IFN-gamma by C. pneumoniae infected PBMC should be further studied as a biomarker of persistent infection in humans.

CD4+ T effector memory cell responses in Chlamydia pneumoniae‐stimulated peripheral blood mononuclear cells in nonasthmatic subjects

“…Circulating memory cells responsive to chlamydial antigen are found in humans 10 . Following C. pneumoniae infection, TEMS may play a role in immune‐protection and pathology; these cells may indicate either past or persistent infection 11 . Smith‐Norowitz et al 11 demonstrated in healthy individuals, that C. pneumoniae ‐induced PBMC IFN‐gamma+ responses increased numbers of CD4 + IL‐2 + and CD4 + IL‐4 + TEMS, while CD8 + IL‐2 + and CD8 + IL‐4 + TEMS decreased.…”

“…Following C. pneumoniae infection, TEMS may play a role in immune‐protection and pathology; these cells may indicate either past or persistent infection 11 . Smith‐Norowitz et al 11 demonstrated in healthy individuals, that C. pneumoniae ‐induced PBMC IFN‐gamma+ responses increased numbers of CD4 + IL‐2 + and CD4 + IL‐4 + TEMS, while CD8 + IL‐2 + and CD8 + IL‐4 + TEMS decreased. However, little is known about the role of C. pneumoniae ‐specific TEMS in humans 10 ; pathogen‐specific TEMS may have a key role in immune control of persistent virus infection 10 .…”

“…Cells were cultured (48h), as previously described. 11 All patients were White, and nonasthmatic. Single-and dual-color immunophenotyping of lymphocytes was performed, with modifications for intracellular staining for cytokines.…”

“…11 Distributions of lymphocytes and TEMS (CD4 + , CD8 + , CD45RA + , CD45RO + , CCR7 + , CD154 + ) and intracellular cytokine (IFN-gamma) were determined (flow microfluorimetry) (Coulter Epics XL, MCL Flow Cytometer; Coulter), as previously described. 11 CD4 + T effector memory cell responses in C. pneumoniae-stimulated PBMC are shown in Table 1. No statistical significances were observed between cell subsets listed (CD4 + TCM, CD4 + TEMRA, CD4 + TEM Total, TEM IFN-gamma, TEMRA IFN-gamma, TEM Total IFN-gamma) (p = 0.202, 1.00, 0.779, 0.368, 0.717, 0.223, respectively) for all stimulation conditions (unstimulated, 1:10, or 1:100) (Friedman χ 2 test).…”

“…14 Virus-specific TEMS have been described in other persistent infections (i.e., Epstein Barr virus, Adenovirus, HIV). 11 This study examines different lymphocyte subpopulations in a C. pneumoniae-infection PBMC model. These findings show that numbers of TEMS, TEMRAs or TCMs did not change between stimulation conditions in this model system.…”