Example of inflammation as a response to bacterial infection.

1. Pattern receptors on mast cells in the tissue recognize and
bind to bacterial antigen. The mast cells release signaling molecules
(blue dots) that cause arterioles to widen. The resulting
increase in blood flow reddens and warms the tissue.
2. The signaling molecules also increase capillary permeability,
which allows phagocytes to squeeze through the vessel
walls into the tissue. Plasma proteins leak out of the capillaries,
and the tissue swells with fluid.
3.  Bacterial antigens activate complement (purple dots).
Activated complement binds to the bacteria.
4.  Phagocytes in the tissue recognize and engulf the complement-
coated bacteria.