Andrew was exposed to the chicken pox virus as a child. What happened to that virus after it crossed the blood-brain barrier and entered Andrew’s brain? a. Nothing happened at first, but the virus remained there and caused negative effects for Andrew as he got older. b. Nothing happened since the chicken pox virus cannot cross the blood-brain barrier. c. The glia in his brain engulfed the virus and then natural killer cells destroyed them both. d. Andrew’s natural killer cells were able to quickly destroy it.