From the REG:
Ongoing Special Abilities > Ignore or Repel > Special Conditions
• A stalemate results when an ignore card is played after and against an immunity card. However, if the ignore card is played before the immunity card, the ignore will win. In other words, a character can’t become immune to a character that is already ignoring that character. Conversely, a character that is already immune continues to be immune even if ignored. Therefore, the result is a stalemate.