Lecture 2 Flashcards
T-Cells
Develop and mature in the thymus; when a mature T cell is Ag-stimulated, it gives rise to cellular immunity
B-Cells
Develop and mature in the bone marrow and gives rise to humoral immunity (immunity that involves production of soluble molecules called immunoglobulins); recognize soluble Ags and develop into Ab-secreting cells
Humoral Adaptive Immunity
Mediated by Abs in the blood and mucosal secretions which are produced by B-cells; Abs recognize microbial Ags, neutralize the infectivity of the microbes, and target microbes for elimination by various effector mechanisms
Cellular Immunity (Cell-Mediated)
Controlled by responses of T-cells which often function in concert with Ag-presenting cells and phagocytes to eliminate microbes; mediates host defense against intracellular microbes, such as viruses and some bacteria, where they are inaccessible to circulating Abs; functions to kill infected host cells to eliminate reservoirs of infection
T-Helper Cells
Help B-cells to make effective Abs thus contributing to eradication of extracellular microbes; also activate tissue-resident macrophages to kill phagocytized microbes or cytotoxic T cells to directly destroy infected cells in cellular immunity; recognize Ags on the surfaces of Ag-presenting cells and secrete cytokines; express CD4 and provide help for B cell growth and differentiation
Paul Ehrlich
“Father of Humoral Immunity”; postulated that immune cells can secrete receptors which recognize microbial toxins and combat invading microbes; also coined the term Abs for the serum proteins that bind toxins
Elie Metchnikoff
“Father of Cell-Mediated Immunity”; discovered special immune cells and named them phagocytes which, he believed, are the principal effector mechanism of immunity; was unable to prove that specific immunity to microbes could be mediated by cells
Specificity
Ensures that the immune response to a microbe (or non microbial Ags) is selective to that microbe (or Ag)
Diversity
Enables the immune system to respond to a large variety of Ags
Memory
Increases the ability to combat repeat infections by the same microbe
Clonal Expansion
Increases the number of Ag-specific cells to keep pace with microbes
Specialization
Generates responses that are optimal for defense against different types of microbes
Contraction and Homeostasis
Allows the immune system to recover from one response so that it can effectively respond to newly encountered Ags
Nonreactivity to Self
Prevents injury to the host during responses to foreign Ags
Clonal Selection Hypothesis
Ag-specific clones of lymphocytes develop before and independent of exposure to Ag; the immune system generates a very large number of clones during the maturation of lymphocytes, thus maximizing the potential for recognizing diverse microbes; each Ag selects a preexisting clone of specific B-cells and stimulates the proliferation and differentiation of that clone (same principle applies to T-cells)
