KEY CONCEPT The immune system has many responses to pathogens and foreign cells.

Many body systems work to produce nonspecific responses. Nonspecific responses are the same for every pathogen. In inflammation, blood vessels become leaky. white blood cells move toward infection and damaged tissue capillary wall extracellular space white blood cell characterized by swelling, redness, and pain

In fever, body temperature increases. Low fevers stimulate white blood cells to mature. High fevers can cause seizure, brain damage, and even death.

Cells of the immune system produce specific responses. Specific immune responses begin with the detection of antigens. Antigens are surface proteins on pathogens. Each pathogen has a different antigen. virus antigens

Specific responses produce memory cells. B cell T cell specialized T and B cells provide acquired (active) immunity

The immune system rejects foreign tissues. Tissue rejection occurs in organ or tissue transplants. Tissue rejection is the result of an immune response. immune system detects protein markers on the donor tissue makes antibodies against the donor’s tissue