Methods of modulating immune responses are provided, including contacting SLAT or IP3R1 with an agent that modulates binding of SLAT to IP3R1. Methods of modulating activation or differentiation of CD4+ T cells are also provided, including contacting SLAT or IP3R1 with an agent that modulates binding of SLAT to IP3R1. Peptides and fragments of an IP3R1 amino acid sequence that binds to a SLAT amino acid sequence, and peptides and fragments of a SLAT amino acid sequence that binds to am IP3R1 amino acid sequence, are further provided.
