Given that the function of HLA is to present peptides to T cells for recognition via T cell receptors (TCR), the association of HLA-DRB1*15:01 with MS development suggests a role for class II-presented peptides and autoreactive CD4+ T cell responses and has led to substantial investigation of the autoantigens responsible for priming of pathogenic responses. Here, CD4 is linked to myeloid sarcoma.