Thanks for your miserly comment. I am glad to have had that little put down from someone that has nothing to add to the conversation or possibly the world. This is because this serves as a reminder that I am not like that, as a rule, taking miserly pot shots at others, as some seem to do, including you.

The most charitable thing you can say about "only those with over-active immune systems survived the 14th century plagues" is that it's so broad as to be meaningless. (Might you perhaps have been thinking of Familial Mediterranean Fever?)

Y.pestis is very good at evading the innate immune response (to the point of reproducing inside macrophages and neutrophils) and likes hanging out in lymph nodes. What kind of increased activity would help here?