The invention relates to the treatment of mycobacterial infections, autoimmune disorders, lymphoproliferative disorders and induction of immunosuppression following transplantation using coronin 1 and modulators of coronin 1. Particular modulators of coronin 1 are compounds which inhibit the production of coronin 1 or the formation of active coronin 1 from a coronin 1 precursor, partly or entirely inactivate coronin 1, inhibit concentration of coronin 1 at the site of T cell activation, or inhibit the coronin 1 mediated signaling pathway downstream of the T cell receptor. Examples of such modulators are antibody or antibody fragments, coronin 1 peptide fragments or corresponding phosphopeptides, or anti-sense oligonucleotides, e.g. siRNA or shRNA. The invention further relates to a method of screening for a compound effective in the treatment of mycobacterial infections, autoimmune disorders, lymphoproliferative disorders and induction of immunosuppression following transplantation comprising contacting a candidate compound with coronin 1 or coronin 1 expressing cells, and selecting appropriate compounds.