When examined by LSCM, IL-2-dependent CD4+ T cell lines derived from two unrelated individuals with CHS contained CD63+ compartments that were characteristically reduced in number, often enlarged and co-labelled for cathepsin D, CTLA-4 and FasL (Fig. 3a) as reported previously [32], [34]. Here, CTLA4 is linked to Chédiak-Higashi syndrome.