The scabs that close cuts in our skin and help them heal, sneezing and itchiness from allergies, swelling and bruises are all signs of our immune system working to keep us well.  Immunologists like Kent Teague study the ways the immune system keeps us healthy and how it acts when we are ill or under other types of stress. Immunologist Martha Zúñiga studies the major histocompatibility complex (MHC), looking at the different ways our immune systems and those of mice respond to transplants.