CD4 and systemic lupus erythematosus: One study has demonstrated a direct link between the development of anti-DNA and the HLA-DRB1 ∗ 1501(DR2) allele polymorphism in SLE patients (Podrebarac, Boisert & Goldstein, 1998), implying a breakdown of immunological tolerance against self-antigens, most likely through aberrant MHC class II dependent activation of auto-reactive CD4+ T cells.