CD4 and AIDS: Hence, the required CD4 and ACE2 primary receptors for HIV-1 and SARS-CoV-2 entry into CD4+ T-lymphocytes and CD133+ ESPC respectively with the targeted cells not only become pathogenically susceptible to the particular virus but also indirectly affect the CD34+ HSPC (in HIV/AIDS) and CD4+/CD19+ T/B-lymphocytes (in SARS-CoV-2/COVID-19) respectively.