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The Aggregatibacter actinomycetemcomitans heat shock protein GroEL interacts directly with human peripheral blood T cells
Heat shock family protein GroEL of Aggregatibacter actinomycetemcomitans (Aa) has antigenic properties. We previously demonstrated that A. actinomycetemcomitans GroEL-like protein affects human CD4 T cells by converting them into IL-10 and IFNg double cytokine producing Tbet+ Th1 cells. The objective of this study was to investigate whether or not AaGroEL communicates with T cells directly. To do this, sorted cells from peripheral blood mononuclear cells were stimulated with AaGroEL for 48 h. Flow cytometry was used to measure soluble and intracellular cytokine expression in the cell cultures and detect TLR2 expression on the surface of T cells. Expression of six different soluble cytokines was evaluated by CBA assay. To determine whether AaGroEL affects CD3+ T cells directly or not, purified CD3+ T cells or CD14+ cells were cultured with AaGroEL separately, and the quantity of soluble cytokine was measured. Results showed that sorted CD3+ cells produced soluble IL-6, TNF alpha, and IFN gamma cytokines. Additionally, the intracellular cytokine staining data showed that AaGroEL-stimulated CD3+ cells were also TNF alpha- and IFN gamma-positive. Moreover, AaGroEL-responsive T cells slightly increased their TLR2 expression. These findings suggest that CD3+ T cells produce cytokines in response to AaGroEL protein without requirements for other cells, such as CD14+ monocytes.