Figure 1: Schematic structure of T cell co-inhibitory receptors The domain structures of the following co-inhibitory receptors are schematically depicted: B- and T-lymphocyte attenuator (BTLA), Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4), Lymphocyte-activation gene 3 (LAG-3), Leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1), sialic acid binding Ig-like lectins (Siglecs), T-cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT), T cell immunoglobulin mucin-3 (TIM-3). Extracellular immunoglobulin domains of coinhibitory receptors include Ig-like (Ig), V-type, C2-type and I-type. ITIM- immunoreceptor tyrosine-based inhibition motif, ITSM-immunoreceptor tyrosine-based switch motif.