HLA-DRB1 and asthma: The frequency of HLA-DRB1*13 in Alternaria-sensitive moderate-severe asthma was significantly increased compared to individuals in the dbMHC data base http://www.ncbi.nlm.nih.gov/projects/mhc/ihwg.cgi, HLA-DRB1*13 ranged from 0.5% of 1330 individuals in North America to 9.8% of 2587 individuals in Europe (p < 0.0001).