Medical Genetics Microorganisms are the principa nonself entities, but neoplasms transplants, and certain foreign substances(eg, some toxins) are also important. To accomplish its tasks, the immune system has evolved two mechanisms: nonspecific immunity and specific immunity which are linked to and influence each otherMedical Genetics Microorganisms are the principal nonself entities, but neoplasms, transplants, and certain foreign substances (eg, some toxins) are also important. To accomplish its tasks, the immune system has evolved two mechanisms: nonspecific immunity and specific immunity, which are linked to and influence each other