In response to exposure to antigen, T cells whose T cell receptor (TCR) are capable of recognizing the self MHC-antigen derived peptide complex, respond to the antigen and differentiate into one of several subsets, namely TH1, TH2, TH17, Treg, etc. characterized by the signature cytokine they secrete, namely IFN-γ, IL-4, IL-17 or IL-10, respectively, referred to as syngeneic polarization as the MHC presenting the foreign antigen/epitope is self-derived.
T cell responses following incubation for defined periods, usually 3 days for mouse splenocytes, are routinely measured by assessing the antigen-stimulated proliferation of T cells by measuring the radiolabeled precursor thymidine incorporated into the genomic DNA of the dividing T cell; the direction of polarization is assessed by measuring the cytokine produced by the proliferating or non-proliferating responding T cells using ELISA of culture supernatants or by intracellular cytokine staining followed by flow cytometry.
In the protocols detailed below, we describe the use of syngeneic mouse bone marrow-derived primary dendritic cells (BMDC) as APC to stimulate spleen derived T cells. The proliferative response of the T cells is measured by incorporation of radiolabeled precursor thymidine into the genomic DNA and their direction of polarization is assessed by measuring the cytokines they secrete, namely IFN-γ, IL-4 and IL-17 over a 72 h period using ELISA. In addition, we used flow cytometry after intracellular cytokine staining to detect IL-17 positive T cells within the CD3+/CD4+/CD25low population. Prior live infection of BMDC with strains of Mycobacterium bovis- Bacille Calmette Guerin (BCG) was used as antigen to pre-condition the BMDC that presented antigens derived therefrom to T cells. We also measured cytokines secreted within 6 to 8 h of BCG infection by BMDC in order to correlate the BMDC cytokine profile with subsequent direction of T cell polarization.
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