CD4 and HIV infectious disease: Exogenous HA (both LMW and HMW) has been reported to reduce HIV infection of CD4+ T cells, while enzymatic reduction of endogenous HA on the surface of CD4+ T cells increases their susceptibility to infection.10 On the other hand, endogenous HA on fibroblastic reticular cells (FRC) can help these cells trans-infect CD4+ T cells in secondary lymphoid organs.11 Therefore, whether HA helps or hinders HIV infection may be context-dependent.