A3 serotype is a secondary risk factor for myasthenia gravis[4] and lower CD8+ levels in hemochromatosis patients.

[7] HLA-A3 selects HIV evolution for a mutation Gag KK9 epitope and results in a rapid decline in the CD8 T-cell response.

[8] This type of evolved response may not be specific for HLA-A3 and since HIV is capable of adapting quickly in situ to selective factors.

A*03:01 modulates increased risk for multiple sclerosis[10] A3-B7 is part of the A3~DQ2 superhaplotype A3-B8 (Romania, svanS) A3~B35 (Bulgaria, Croatia, E. Black Sea) A3~B55 (E. Black Sea) A3~B7 is bimodal in frequency in Europe with one node in Ireland and the other in Switzerland, relatively speaking Switzerland appears to be higher.

A3~Cw7~B7 is one of the most common multigene haplotypes in the western world, particularly in Central and Eastern Europe.