The effects of age on CD4+ T cell TLR-2 expression and TLR-2 mediated direct co-stimulation (122.6)

Abstract

Abstract Background: Functional Toll like receptors (TLR) are found on human T cells. Neonatal antigen presenting cells (APC) have altered responses to TLR ligands; it is unknown if neonatal CD4+ T cell TLR responses are comparable to adult. Objective: Comparison of TLR-2 expression and responsiveness to TLR-2 direct co-stimulation among total and naïve CD4+ T cell subsets from neonates and adults. Methods: T cell subsets (CD3+CD4+ or CD3+CD4+CD45RA+) were isolated from cord and adult peripheral blood mononuclear cells by flow sorting ( >99.5% purity) and cultured in an APC-free model with α-CD3 ± α -CD28 ± TLR-2 ligand Pam3CYS4. Quantitative PCR and ELISA determined TLR-2 expression and cytokine production. Results: Neonatal CD4+ T cells are predominately naïve (97.2% CD45RA+) but express 5-fold more TLR-2 mRNA than adult CD4+ T cells. Pam3CYS4 provides direct co-stimulation in the presence of α-CD3 to adult and neonatal total CD4+ T cells resulting in IL-2, TNF-α, and IFN-γ production; provision of additional co-stimulation (α-CD28) further enhances cytokine production. When comparing total CD4+ T cell populations, neonatal cells generate significantly less cytokines than adult. When naïve neonatal and adult T cells are compared, neonatal cells generate more cytokines in response to TLR-2 mediated co-stimulation. Conclusions: Naïve neonatal CD4+ T cells have enhanced TLR-2 expression and increased sensitivity to direct TLR-2 co-stimulation as compared to naïve adult cells.