CD4 and rosacea: Additionally, the proportion of classical monocytes decreased following treatment.[36] HLA-DR is a key member of the major histocompatibility complex class II (MHC II) molecule family, responsible for presenting exogenous antigens and initiating the adaptive immune response mediated by CD4+ T cells.[37,38] We speculate that HLA-DR plays a critical role in the pathogenesis of rosacea.