Immunology Questions and Answers – Primary Lymphoid Organs

This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Primary Lymphoid Organs”.

1. The bone marrow of which bone is not an active site for hematopoiesis?
a) Femur
b) Humerus
c) Scapula
d) Ileum
View Answer

Answer: c
Explanation: Bone marrow is majorly contained by all bones but bones which are active in hematopoiesis are long bones such as femur and humerus, sternum and the hip bone Ileum.

2. In adults, what is the primary site of hematopoiesis?
a) Bone marrow
b) Liver
c) Lungs
d) Heart
View Answer

Answer: a
Explanation: In adults, all the hematopoietic cells reside in the bone marrow and also develop in the bone marrow. At earlier stages of life, these cells are distributed in various other organs, but as adult life approaches, the HSCs develop residence in the bone marrow.

3. Which of the following cell types is NOT present in the Bone Marrow?
a) Osteobalsts
b) Dendritic cells
c) Reticular cells
d) Sympathetic neurons
View Answer

Answer: b
Explanation: An adult bone marrow, in general, contains four types of cells namely: osteoblasts, endothelial cells, reticular cells and sympathetic neurons. Dendritic cells are not a part of bone marrow.

4. In mammals, what is the site of maturation of B-cells?
a) Bursa of Fabricius
b) Bone marrow
c) Lymph nodes
d) Thymus
View Answer

Answer: b
Explanation: In mammals, B cells are born and matured in the Bone marrow. Bursa of Fabricius is the site of maturation of B cells in birds, whereas Thymus is the site of maturation of T cells.

5. State true or false.
An immature B cell will appear far from the osteoblasts in the bone marrow.
a) True
b) False
View Answer

Answer: b
Explanation: The statement is false because as the B cells mature, they migrate far from the osteoblasts. The immature B cells remain close to the osteoblasts in the bone marrow.

6. Who discovered the role of Thymus?
a) Sydney Brenner
b) Robert Koch
c) Thomas H. Morgan
d) J.F.A.P. Miller
View Answer

Answer: d
Explanation: The role of thymus in T cell development was unknown until J.F.A.P. Miller discovered its importance. Earlier, thymus was only considered as the graveyard of cells.

7. The immature thymus cells are called as __________
a) Thrombocytes
b) Thombocytes
c) Thymocytes
d) Thermocytes
View Answer

Answer: c
Explanation: The immature thymus cells are the developing T cells and these are called Thymocytes. Their name is simply based on their location.

8. Which thymocytes are negatively selected in the process of selection?
a) Complexes with no affinity
b) Complexes with too low affinity
c) Complexes with intermediate affinity
d) Complexes with too high affinity
View Answer

Answer: d
Explanation: The T cells (thymocytes) are selected on the basis of peptide complex formation between T cell Receptors and self MHC molecules. If the complex is formed with too high affinity, the respective thymocytes die due to Negative selection.

9. What is the estimated percentage of thymocytes that survive throughout the maturation process?
a) 5%
b) 30%
c) 50%
d) 95%
View Answer

Answer: a
Explanation: The maturation of thymocytes is a long process and many of the thymocytes die in the process. First, the Positive and Negative selection takes place and then many of the thymocytes die due to too low affinity for the MHC molecules. It is only 5% thymocytes that actually survive and mature.

10. The Double Negative thymocytes express the surface markers ___________
a) CD8 and CD4
b) Neither CD8 nor CD4
c) CD4 but not CD8
d) CD8 but not CD4
View Answer

Answer: b
Explanation: The Double Negative (DN) thymocytes are the youngest thymocytes which just enter the thymus. At this stage, the thymocytes do not express any surface markers. The surface markers are associated with the mature T-cells.

11. From where do the T-cell precursors enter the thymus?
a) Thymic medulla
b) Thymic cortex
c) Corticomedullary junction
d) Subcapsular cortex
View Answer

Answer: c
Explanation: The corticomedullary junction (CMJ) or Cortical Medullary Junction is the region from where cells enter and exit to the bloodstream. Hence, this region contains the most immature thymocytes.

12. The thymocytes that express both CD4 and CD8 surface markers are called as ________
a) Single Positive
b) Double Positive
c) Positive Selected
d) Double Selected
View Answer

Answer: b
Explanation: The thymocytes that develop T-cell Receptors and express both CD8 and CD4 surface markers are called Double Positive. In contrast, the immature thymocytes that do not develop TCR and do not express surface markers are called Double Negative.

13. Where is thymus located?
a) Just below the liver
b) Just above the liver
c) Just below the heart
d) Just above the heart
View Answer

Answer: d
Explanation: The thymus is situated just above the heart. Until puberty, it is the largest of size but it is found that thymus begins to shrink after puberty.

14. Thymocytes that express only one of CD4 or CD8 surface markers are called as _______
a) Single Negative
b) Double Negative
c) Single Positive
d) Double Positive
View Answer

Answer: c
Explanation: Few of the mature thymocytes express only one of the surface markers, either CD4 or CD8. Such thymocytes are called Single Positive.

15. What is the function of osteoblasts?
a) Controlling differentiation of HSCs
b) Help in division of HSCs
c) Provide nourishment to HSCs
d) Control the release of HSCs
View Answer

Answer: a
Explanation: Osteoblasts are one of the cells that are present in the bone marrow. Their function is to generate the bone and to control the differentiation of the hematopoietic stem cells.

Sanfoundry Global Education & Learning Series – Immunology.

To practice all areas of Immunology, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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