CD4 and HIV-1 infection: Previously, it has been shown that the introduction of LCK into myeloid cell lines, or the co-introduction of CD4 and LCK in non-lymphoid cell lines which normally do not express either protein, results in association between LCK and CD4, leading to inhibition of CD4 endocytosis, reduction of the CD4 internalization rate, high levels of surface CD4, and an increase in HIV-1 infection [13], [32]–[36].