Expression of IL-4 mRNA in peripheral blood mononuclear cells from normal donors in relation to expression of TLR2

When IL-4 mRNA was distinguished from mRNA encoding its antagonist, the splice variant IL-4δ2, it was found to correlate directly with expression of TLR2 in fresh peripheral blood mononuclear cells (PBMCs) from normal donors (p = 0.0013). Similarly IL-4 mRNA was high when TLR2 mRNA was abundant compared to levels of mRNA encoding its heterodimerisation partners TLR1 (p = 0.0007) or TLR6 (p = 0.0007). IL-4δ2 tended to show the reverse effect; IL-4δ2 mRNA was high when TLR2 was low relative to TLR1 (p = 0.001). When subpopulations of the PBMCs were examined these relationships were found to be restricted to the CD3+ cells. The CD3+ cell population from 5 of 10 donors had detectable TLR2 mRNA. When levels of TLR1, IL-4 and IFN-γ mRNA were assayed in the TLR2^low and TLR2^high CD3+ cells, it was found that IL-4 mRNA was restricted to the TLR2^high T cells (p = 0.007) while TLR1 was higher in the TLR2^low T cells (p = 0.015). IFN-γ was also somewhat increased in the TLR2^low (ns). None of these correlations with TLR mRNA expression levels were found in similar samples from tuberculosis patients, or when similar analyses were performed with data for IL-10 mRNA in cells from the same donors. We conclude that in T cell populations from normal donors, expression of IL-4 (but not of its antagonist, IL-4δ2, or of IL-10) is associated with high TLR2 and low TLR1.