What pen studies how host organisms safeguard themselves against microbial infection?

What pen studies how host organisms safeguard themselves against microbial infection?
Immunology
when one goes out within the back patio and see how the red ants attack or defend themselves against the black ants.
Gurl, I hope you don't mind my daffy, silly answers.
immunology
micro biological studies, afterwards you would have to specialize within Parasitic organisms.
microbilogy, IMMUNOLOGY, and pathology dear!!
Microbiology. I know this because I took a whole semester of it.
microbiology