<prompt> Antigen presented along with HLA-ll stimulatesCD8 cellsCD4cellsCD2 cellsCD19 cells  <response>: Ref Robbins 9e p195 Class II MHC molecules are encoded by genes in the HLA-D region, which contains at least three subregions: DP, DQ, and DR. Class II MHC molecules are heterodi- mers of noncovalently linked polymorphic a and b sub- units Fig. 4-3. The extracellular poion of the class II MHC heterodimer contains a cleft for the binding of antigenic peptides and a region that binds CD4. Class II MHC expression is restricted to a few types of cells, mainly APCs notably, dendritic cells , macro- phages, and B cells. In general, class II MHC molecules bind to peptides derived from proteins synthesized outside the cell e.g., those derived from extracellular bacteria and ingested into the cell. This propey allows CD4 T cells to recognize the presence of extracellular pathogens and to orchestrate a protective response. 