HLA antigens

There are 2 main classes of HLA antigens:
Class 1 includes the HLA- A,B ,and C antigens.
Class 2 has the HLA-D antigen, including DR2,DR3, and DR4.

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The DR4 is associated with sever RA
DR2 & DR3 are associated more with SLE(Systemic lupus erythematosis ), and
DR3 is also occasionally found in Sjogren disease & polymyositis.

Reference : MedStudy