 These receptors can be made from alpha+beta sets of two different DQ haplotypes, one set from the maternal and paternal chromosome.If one carries haplotype -A-B- from one parent and -a-b- from the other, that person makes 2 alpha isoforms (A and a) and 2 beta isoforms (B and b).This can produce 4 slightly different receptor heterodimers (or more simply, DQ isoforms).