In humans, CTLA-4 deficiency caused by autosomal heterozygous mutation of the CTLA-4 gene (Kuehn et al., 2014; Schubert et al., 2014) or mutations in recycling partner LPS-Responsive beige-like anchor (LRBA) protein (Lo et al., 2015) are associated with severe autoimmune diseases. Here, CTLA4 is linked to autoimmune disease.