Giant cell arteritis (GCA) is considered to be a T cell-dependent disease. Autoantibodies have not consistently been found in GCA. The exception is antiphospholipid antibodies (APLA), which were found in 30–80% of GCA cases. Recently, efforts have been made to seek autoantibodies in GCA using newer methods of detection: serological identification of antigens by recombinant cDNA expression cloning, and a proteomic approach. In these studies, lamin C (a nuclear envelope antigen) was recognized by antibodies in 32% of GCA sera and none of the controls. Other autoantigenic proteins were also identified: lamin A, vinculin (a cytoskeleton antigen), and annexin 5 (an endothelial protein). In a recent study, 92% of 36 patients with GCA and/or polymyalgia rheumatica (PMR) had autoantibodies to a human ferritin peptide (the heavy chain N-terminal); 89% had antibodies to bacterial ferritin peptide of Staphylococcus epidermidis. The significance of these findings needs to be studied further. GCA may be a part of the newly described ASIA syndrome (autoimmune syndrome induced by adjuvants). A recent study from Italy reported 10 cases of GCA/PMR within 3 months of influenza vaccination. These comprised 50% of all cases of GCA/PMR diagnosed during the 6 year period of the study. Another 11 cases of GCA following influenza vaccinations were reported. GCA pathogenesis involves all branches of the immune system, including antigen-presenting cells, T cells and B cells, and autoantibody formation is not uncommon. GCA etiology remains unknown, but may be associated with exposure to bacterial or viral antigens.