Immunology Exam 1 Part 2

1. Immunology Exam 1Part 2 Created by: Laura Wilson

2. Where are lymphoid stem cells produced in older fetuses and neonates? • Bone marrow

3. In mammals, where do T cells mature? • Thymus

4. In mammals, where do B lymphocytes mature? • Bone marrow

5. The classification of lymphoid organs and tissues is based on: • The level to which they participate in the maturation of lymphocytes • Provision of a suitable environment for the interaction between foreign antigen and antigen-sensitive T and B lymphocytes

6. What makes up the central (primary or generative) lymphoid organs and tissues? • Thymus • Bone marrow (mammals) • Bursa of Fabricius (avian)

7. What are the functions of the central lymphoid organs and tissues? • Regulate production and maturation of lymphocytes, ie, generate lymphocytes that are individually different, the concept being “one cell, one specificity”

8. T/F • All of the central lymphoid organs regress with age

9. False • All but bone marrow regress with age

10. Mature lymphocytes acquire __ __ __ and other ___ ____ and learn to discriminate btwn self antigens, which are tolerated, and foreign antigens, which, generally are not • Specific antigen receptors • Phenotypic characteristics

11. Maturation and differentiation of lymphocytes occur: • Independent of foreign antigenic stimulation

12. What happens with removal of the central lymphoid organs early in life? • Loss of lymphocytes • Loss of immune responsiveness

13. Where is the thymus found? • Anterior mediastinal space • In horses, pigs, sheep, cattle, and chickens, it also extends up the neck as far as the thyroid gland

14. The thymus is organized into _____ separated by CT septae. • lobules

15. Part of the thymus that contains about 85% of the total thymocytes, cells here are relatively immature and divide rapidly • Cortex (outer thymic zone)

16. Part of the thymus containing mostly mature lymphocytes • Medulla

17. T/F • Thymic epithelial cells are found throughout the thymus

18. True

19. T/F • Interdigitating dendritic cells (IDCs) and macrophages are found in the thymic lobules

20. True • Particularly where? • At the coricomedullary junction

21. Where are interdigitating dendritic cells (IDCs) and macrophages derived from? • Bone marrow

22. Where does thymic involution begin? • Within the cortex which may disappear completely, whereas medullary remnants persist.

23. What is corical atrophy related to? • Corticosteroid sensitivity [lysis] of the immature cortical thymocytes

24. What occurs following neonatal thymectomy of day-old mice? • Total loss of cell-mediated immune response • B cell response to protein antigens is significantly impaired

25. When stem cells migrate to the thymus, they acquire: • Antigen receptors (TCRs) and other functional and phenotypic characteristics of mature T cells

26. What causes the functional and phenotypic changes in T cell maturation? • The influence of cytokines and thymic hormones

27. Where are cytokines and thymic hormones produced in the thymus? • Thymic epithelial cells

28. The phenotypic markers appear on the developing T cell membrane as _____ at different stages of differentiation in the thymus • Proteins

29. Maturation of stem cells begins in the ____, and as thymocytes mature, they migrate toward the ______. • Cortex • Medulla

30. T/F • Only mature T cells exit the thymus and enter the blood and peripheral lymphoid tissues

31. True

32. Positive and negative cell selection of thymocytes is a function of: • Thymic epithelial cells • IDCs • macrophages

33. Which thymocytes undergo positive selection? • Thymocytes that express functional CD4 or CD8 molecules, ie, recognize self MHC I and II molecules • Thymocytes that express TCRs that have weak affinity for self-peptides

34. Which thymocytes undergo negative selection? • Thymocytes that DO NOT express CD4 or CD8 molecules • Thymocytes that DO NOT express TCRs or express TCRs that cannot bind weakly to self peptides • Thymocytes that express TCRs that have strong affinity for self-peptides • (Cell death may occur via neglect or by apoptosis)

35. The process of + and – selection effectively eliminates most T cells in the thymus, to the extent that >__% of the developing T cells die in the thymus • 90

36. Apoptotic thymocytes are phagocytosed by: • Thymic macrophages

37. Definition: • Lymphoepithelial organ found in birds but not in mammals; observed as a sac-like structure dorsal to the cloaca

38. Bursa of Fabricius (BF)

39. When does the BF reach maximum size? • 1-2 weeks after hatching (followed by gradual involution)

40. By the time the bird reaches _____ age, only atrophied vestiges remain of the BF and thymus. • 6 months (sexual maturity)

41. What occurs following a bursectomy of day-old chicks? • Only a slight drop in the numbers of circulating lymphocytes • Dramatic decline in Ab immune response • Slight to no effect on cell-mediated immunity

42. T/F • Peripheral (secondary) lymphoid organs arise late in fetal life and persist through adulthood

43. True

44. T/F • Removal of any of the peripheral lymphoid organs significantly reduces an individual or animal’s immune capacity

45. False • It does not significantly reduce it

46. The sites where mature lymphocytes response to foreign antigens are initiated and develop. • Peripheral Lymphoid Organs

47. Adaptive immune responses to antigens entering the body via the skin and mucosa, or from parenchymal organs and CTs are initiated in the: • Lymph nodes

48. T/F • The majority of B cells die through apoptosis

49. True • (95-99%)—a reflection of negative selection of self-reactive B cells

50. T/F • Positively selected B cells seed the peripheral lymphoid organs and tissues