MICROANATOMY

Detailed explanation-1: -Infectious diseases are caused by pathogens, which include bacteria, fungi, protozoa, worms, viruses, and even infectious proteins called prions. Pathogens of all classes must have mechanisms for entering their host and for evading immediate destruction by the host immune system. Most bacteria are not pathogenic.

Detailed explanation-2: -Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys, or tries to destroy, substances that contain antigens.

Detailed explanation-3: -White blood cells move through blood and tissue throughout your body, looking for foreign invaders (microbes) such as bacteria, viruses, parasites and fungi. When they find them, they launch an immune attack.

Detailed explanation-4: -The non-self particles and foreign bodies that are infectious or pathogenic, like bacteria, viruses, and parasites, make proteins called antigens that allow the human body to know that they intend to cause damage. Antigens are anything that causes an immune response.

Detailed explanation-5: -Antigen: A foreign substance (such as bacteria or virus) in the body that is capable of causing disease. The pres-ence of antigen in the body triggers an immune response, usually the production of antibodies.