Auto-immuno-deficiency syndromes

Autoimmune diseases constitute a broad, heterogenous group with many diverse and often overlapping symptoms. Even so, they are traditionally classified as either systemic, rheumatic diseases or organ-directed diseases. Several theories exist about autoimmune diseases, including defective self-recognition, altered self, molecular mimicry, bystander activation and epitope spreading. While there is no consensus about these theories, it is generally accepted that genetic, pre-disposing factors in combination with environmental factors can result in autoimmune disease. The relative contribution of genetic and environmental factors varies between diseases, as does the significance of individual contributing factors within related diseases. Among the genetic factors, molecules involved in antigen (Ag) recognition, processing, and presentation stand out (e.g., MHC I and II) together with molecules involved in immune signaling and regulation of cellular interactions (i.e., immuno-phenotypes). Also, various immuno-deficiencies have been linked to development of autoimmune diseases. Among the environmental factors, infections (e.g., viruses) have attracted most attention, but factors modulating the immune system have also been the subject of much research (e.g., sunlight and vitamin D). Multiple sclerosis currently stands out due to a very strong and proven association with Epstein-Barr virus infection, notably in cases of late infection and in cases of EBV-associated mononucleosis. Thus, a common picture is emerging that both systemic and organ-directed autoimmune diseases may appropriately be described as auto-immuno-deficiency syndromes (AIdeSs), a concept that emphasizes and integrates existing knowledge on the role of immuno-deficiencies and chronic infections with development of overlapping disease syndromes with variable frequencies of autoantibodies and/or autoreactive T cells. This review integrates and exemplifies current knowledge on the interplay of genetically determined immuno-phenotypes and chronic infections in the development of AIdeSs.