The results of the long/short coculture of human CD34+ cells and derivatives with OP9-DL1 cells in the presence of HIV-1 indicate that the dynamics of CD34+CD7+ lymphoid progenitors may be affected in a CXCR4-associated manner and more quickly than CD34−CD4+ thymocytes and T cells despite the lower susceptibility of CD34+CD7+ cells to HIV-1 infection as suggested by their lower CD4+ frequencies. The gene discussed is CD4; the disease is HIV-1 infection.