Analysis of HLA class II polymorphism revealed DR2 as the most frequen
t antigen in Croatians (20, 9%). The observed DR2 subtypes and their f
requencies were as follows: DRB1160l - 9.9%; 1501 - 8.5%; 1602 - 1.8%
, 1502 - 1.4% and 1503 - 0.7%. Furthermore, analysis of probable DRB1-
DQA1-DQB1 haplotype associations in unrelated individuals revealed a h
igh diversity of DR15 haplotype associations. Now, to confirm this obs
ervation from unrelated individuals, family studies have been performe
d. Sixty-eight families, with at least one parent and one offspring DR
2 positive, have been studied. DRB11601-DQA1*0102-DQB1*0502 seems to
be conserved haplotype in Croatians while DRB115 haplotypes showed ex
tremely high diversity. Seven rare DR15 haplotypes are observed; six o
f these appear twice and one only once. Two haplotypes appear to be un
ique to Croatians: DRB11501-DQA1*0102-DQB1*0501 and DRB1*1501-DQA1*01
02-DQB10604. This confirmation of extremely high diversity of DR15 ha
plotypes in Croatians is a valuable tool for unrelated bone marrow tra
nsplantation and DR2 disease association studies.