CD163 and infection: After the first day of in vivo infection, nonvirulent strains could induce increased levels of CD163 on the surfaces of PAMs, but virulent strains, contrarily, led to a reduced expression of CD163, suggesting that an increased expression of CD163 may indicate that nonvirulent strains are susceptible to phagocytosis and, thereafter, these strains are easily killed by PAMs [14,23].