<P> Human MHC class I and II are also called human leukocyte antigen (HLA). To clarify the usage, some of the biomedical literature uses HLA to refer specifically to the HLA protein molecules and reserves MHC for the region of the genome that encodes for this molecule, but this is not a consistent convention . </P> <P> The most studied HLA genes are the nine classical MHC genes: HLA - A, HLA - B, HLA - C, HLA - DPA1, HLA - DPB1, HLA - DQA1, HLA - DQB1, HLA - DRA, and HLA - DRB1 . In humans, the MHC gene cluster is divided into three regions: classes I, II, and III . The A, B and C genes belong to MHC class I, whereas the six D genes belong to class II . </P> <P> MHC alleles are expressed in codominant fashion . This means the alleles (variants) inherited from both parents are expressed equally: </P> <Ul> <Li> Each person carries 2 alleles of each of the 3 class - I genes, (HLA - A, HLA - B and HLA - C), and so can express six different types of MHC - I (see figure). </Li> <Li> In the class - II locus, each person inherits a pair of HLA - DP genes (DPA1 and DPB1, which encode α and β chains), a couple of genes HLA - DQ (DQA1 and DQB1, for α and β chains), one gene HLA - DRα (DRA1), and one or more genes HLA - DRβ (DRB1 and DRB3, - 4 or - 5). That means that one heterozygous individual can inherit six or eight functioning class - II alleles, three or more from each parent . The role of DQA2 or DQB2 is not verified . The DRB2, DRB6, DRB7, DRB8 and DRB9 are pseudogenes . </Li> </Ul>

Which of the following cells will have class ii mhc proteins