Our skin presents the first barrier to infection, then there are

Our skin presents the first barrier to infection, then there are defenses inside the body which act as early warning systems between the cells and the white blood cells, helping to close down the activity of the viruses.
【正确答案】：我们的皮肤是保护我们免受感染的第一道防线。随后是体内防御系统，它们在细胞和白细胞之间起到一种预警系统的作用，从而帮助阻遏病毒的活动。