Each human cell expresses six MHC class I alleles (one HLA-A, -B, and -C allele from each parent) and six to eight MHC class II alleles (one HLA-DP and -DQ, and one or two HLA-DR from each parent, and combinations of these).
Todas as células humanas expresan seis alelos MHC de clase I (un alelo HLA-A, -B, e -C de cada proxenitor) e de seis a oito alelos MHC de clase II (un alelo HLA-DP e -DQ, e un ou dous HLA-DR de cada proxenitor, e combinacións deles).