Immune-mediated diseases are known to be associated to different human leukocyte antigen (HLA) genetic variants in genes of both class I and class II of the human MHC region. In immune-mediated diseases, we deal with susceptibility rather than dominant or recessive classical genetic transmission, thus the role of HLA variants is often hardly intelligible, leading researchers to often describe the percentage of different alleles without any effort to understand the underlying mechanisms. At present, only a few hypotheses have been put forward, such as the epitope-shared thesis in rheumatoid arthritis or self-attack by the immune system being driven by pathogen-like antigens.

Moreover, there is a lack of guidelines helping researchers and in particular clinicians in handling hundreds of HLA alleles and the biological differences among them. There is therefore an urgent need for research into the development of proposals for new guidelines in collection and managing HLA data, new hypotheses on the mechanisms giving HLA variants such a pivotal role in disease susceptibility, and reviews on the role of HLA alleles in the development of immune-mediated diseases.

The aim of this Special Issue is to attract research showing different perspectives on HLA susceptibility in immune-mediated diseases, and to stimulate researchers to design guidelines to easily handle HLA data in the same manner, helping develop a basis for a homogenous way to report results on HLA genetic data. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Epidemiological studies on the association between immunogenetic markers (genetics and epigenetics of the HLA region) and immune-mediated diseases
• Significance and potential applications of immunogenetic markers in clinical practice for immune-mediated diseases
• In vitro and in vivo models to investigate immunogenetic mechanisms in immune-mediated diseases
• Meta-analyses on the potential applications of HLA genotypes as diagnostic and prognostic markers
• Studies on the inheritance of HLA epigenetic signatures from mother to child in familial clustering immune-mediated diseases
• Guidelines to improve the quality of genetic studies in immune-mediated diseases