HLA-DR sub-types and associated autoimmune conditions

HLA DR sub-types
HLA-DR is a major histocompatibility complex, MHC CLass II cell surface receptor, encoded by the human leukocyte antigen complex on chromosome 6.
HLA-DR is important for understanding of graft-versus host disease, organ transplant rejections, and also involved in several autoimmune conditions, disease susceptibility and disease resistance.

HLA-DR molecules are upregulated in response to signalling. In the instance of an infection, the peptide (such as the staphlococcal enterotoxin I peptide show in the two illustrations) is bound into a DR molecule and presented to a few of a great many T-cell receptors found on T-helper cells. These cells then bind to antigens on the surface of B-cells stimulating B-cell proliferation.

References:
HLA types associated with disease: http://en.wikipedia.org/wiki/HLA_DR
British Transplant Society - Publishes guidelines on ethics, criterias, and guidelines on various transplants: http://www.bts.org.uk/