Animals are under constant threat of microbial invasion. These potential invaders gain access to the body through the intestine and respiratory tract and the skin. The large and diverse microbiota of the intestine serves to protect the intestine from infectious invaders by occupying a niche that precludes other organisms from establishment there. Other potential invaders are infectious agents spread from other individuals.
The function of the immune system is the detection and destruction of invading microorganisms and abnormal cells. Because of the great diversity of microbial invaders, the immune system is a complex mixture of protective mechanisms. These may be simply classified as innate immunity and adaptive immunity. Protection within the first few hours and days of microbial invasion is the responsibility of the “hard wired” innate immune system. Longer-term protection is the responsibility of the adaptive immune system.
Amyloidosis is caused by abnormal deposition of insoluble proteins in tissue. Formation of these proteins is often associated with inflammation. Deposition can lead to organ dysfunction, which can be fatal if critical organs are affected. Diagnosis is based on tissue biopsy. There is no effective treatment once protein deposition has occurred, although decreasing inflammation may slow progression.