Of note, the combination of IGHV4-34 with IGKV3-20, or with the highly homologous IGKV3-15, is found in 90% of CAD patients and results in IgM antibodies with a relatively high affinity for the branched NAL I epitope on erythrocytes clinically leading to pathological red blood cell agglutination (Bhat et al, 2000; Malecka et al, 2016). Here, CD40LG is linked to cold agglutinin disease.