Question 1
Explain the role of exposure to antigens in the development of the immune system in the fetus and in the primary and secondary immune responses in children and adults. How does this compare to the role of innate immunity?Question 2
Describe innate and adaptive immunity.Answer 1
During development, any lymphocytes bearing receptors that bind to molecules in the fetus are eliminated. Thus, the only lymphocytes that persist at birth are those that failed to bind to anything, that is, those that have never encountered an antigen. Once the immune system has matured (early in infancy), primary immune responses develop in response to never-before encountered antigens, and secondary immune responses develop with subsequent exposures to the same antigens. Innate immunity is, at all times, independent of prior antigen exposure.Answer 2
Innate immunity is a nonspecific response to foreign invaders or tissue damage and acts as a second line of defense. Adaptive (acquired) immunity has two major methods of response, cell-mediated immunity and humoral immunity, both of which are specific to the pathogen. Cells of the adaptive immune system are responsible for immunological memory.