Antigens

Before birth, cells inventory the proteins and other large molecules in the body, learning to identify these as "self." The lymphatic system responds to nonself, or foreign antigens, but not normally to self antigens. Receptors on lymphocyte surfaces enable the cells to recognize foreign antigens.

Antigens may be proteins, polysaccharides, glyco-proteins, or glycolipids. The antigens that are most effective in eliciting an immune response are large and complex, with few repeating parts. Sometimes, a smaller molecule that cannot by itself stimulate an immune response combines with a larger one, which makes it able to do so (antigenic). Such a small molecule is called a hapten (hap'ten). Stimulated lymphocytes react either to the hapten or to the larger molecule of the combination. Haptens are found in certain drugs, such as penicillin; in household and industrial chemicals; in dust particles; and in products of animal skins (dander).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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