Membrane expression of the main HIV-1 receptors and co-receptors on trophoblastic cells isolated from 10 early placentas. 3a (Table 3): Membrane expression is indicated as the percentage of positive cells after immunostaining for CD4 and for the β-chemokine receptors CCR3, CXCR4 and CCR5, as shown by immunostaining using MoAb and FACS analysis