Measurement of CD40 ligand (CD154) expression on resting and in vitro-activated T cells.

Measurement of the ability of in vitro activated T lymphocytes to express CD40 ligand (CD154) is a valuable tool for diagnosis of the X-linked hyper-IgM syndrome (XHIM) and for investigating abnormalities in the costimulatory functions of T lymphocytes. Resting peripheral blood lymphocytes do not normally express any appreciable levels of CD154, necessitating in vitro activation. This unit details the in vitro activation procedure, the three-color monoclonal antibody panels used to label the appropriate lymphocyte subsets, the controls required to interpret the assay, the setup and acquisition of listmode data files, and the gating and analysis protocols used to interpret the data.