CD4 and infection: HLA class II molecules are expressed in antigen presenting cells such asB-lymphocytes, and act to present exogenous antigens to CD4+ helper T-cells.Efficiency of antigen presentation may influence lymphomagenesis through effects onanti-tumor immunity or on immune response to infections that are directly orindirectly oncogenic (e.g., through viral genome insertion or nonspecific chronicantigenic stimulation) [19].