lymphoid

Question 1

What are the main components of the lymphatic system?

Answer 1

1. Lymphatic vessels
2. Secondary lymphoid tissue (dominant tissue in the body)

Question 2

What are the types of lymphoid tissue?

Answer 2

Primary, Secondary, Tertiary

Question 3

How do immune cells migrate around the body?

Answer 3

Immune cells reside in immune organs or other tissue sites and use both lymphatic and cardiovascular circulation for migration.

Question 4

What is the function of primary lymphoid tissue?

Answer 4

Site of lymphopoiesis (lymphocyte production)

Question 5

What types of lymphocytes are produced in primary lymphoid tissue?

Answer 5

B cells, T cells, Natural killer cells

Question 6

What are the primary lymphoid organs?

Answer 6

Bone marrow, Thymus, Foetal liver

Question 7

Which cells are involved in adaptive immunity?

Answer 7

B cells and T cells

Question 8

What is unique about B and T cell receptors?

Answer 8

They are specific and cover a vast range of unique receptors.

Question 9

What happens during a secondary immune response?

Answer 9

Memory cells enable rapid expansion of the immune response.

Question 10

What is the B cell receptor and how does it diversify?

Answer 10

B cell receptor = antibody = immunoglobulin. Diversification: Heavy chain: 1/40 V, 1/24 D, 1/6 J regions; Light chain: 1/46 V, 1/5 J regions

Question 11

What is the T cell receptor and its structure?

Answer 11

T cell receptor = TCR heterodimer (αβ or γδ). No further diversification after maturation.

Question 12

What are the gene region combinations for TCR?

Answer 12

TCR alpha: 1/45 V, 1/45 J regions; TCR beta: 1/46 V, 2 D, 13 J regions

Question 13

What happens to gene regions once B and T cells mature?

Answer 13

Only one V (IV), one D (ID), and one J (IS) region per gene is retained.

Question 14

What is the primary function of the bone marrow?

Answer 14

It is the primary site of haematopoiesis (blood cell formation).

Question 15

What happens in the bone marrow during infection?

Answer 15

It increases production of immune cells.

Question 16

Where is the B cell repertoire generated?

Answer 16

In the bone marrow.

Question 17

Where do B cells undergo final maturation?

Answer 17

In the periphery (outside the bone marrow).

Question 18

What is meant by ‘repertoire’ in immunology?

Answer 18

The range of genetically different BCR or TCR in a host. A larger repertoire allows recognition of more threats.

Question 19

What happens to immature T cells in the thymus?

Answer 19

They undergo stepwise differentiation into mature T cells.

Question 20

What is positive selection in the thymus?

Answer 20

Tests if the T cell has a TCR that can generate a signal. If not, the cell undergoes apoptosis.

Question 21

What is negative selection in the thymus?

Answer 21

Tests if the T cell reacts against self-antigens. If it does, it is eliminated.

Question 22

What happens after final selection in the thymus?

Answer 22

Mature T cells exit the thymus.

Question 23

How does thymus activity change with age?

Answer 23

Declines with age, leading to reduced TCR and changes in thymus structure and mass.

Question 24

What is the role of secondary lymphoid tissue?

Answer 24

It is where lymphocytes interact with antigens and other lymphocytes to generate an immune response.

Question 25

What are examples of secondary lymphoid tissues?

Answer 25

Spleen, lymph nodes, appendix, and mucosal-associated lymphoid tissue (MALT).

Question 26

How is secondary lymphoid tissue organized?

Answer 26

Distributed around the body, interconnected via lymphatic and blood systems. Can be discrete organs or regions in tissue. Highly organized to bring immune cells close to antigens.

Question 27

What are the structural features of lymph nodes?

Answer 27

Distinct T and B cell zones; Afferent (in) and efferent (out) lymph flow; Connected to lymphatic system; Arterial and venous connections; B cells reside in germinal centers and migrate upon antigen interaction.

Question 28

What are the structural features of the spleen?

Answer 28

Distinct T and B cell zones; Afferent and efferent lymph flow; Arterial and venous connections; Arterioles provide flow into white pulp.

Question 29

What is the role of epithelial barriers in immunity?

Answer 29

First line of defense against infection; act as physical barriers; have an extensive lymphatic network; increased conc in proximal external regions.

Question 30

What is Gut-associated Lymphoid Tissue (GALT)?

Answer 30

Specialized secondary lymphoid tissue; includes Peyer's patches found below epithelium (e.g., ileum, small intestine); follicles contain many B cells and frequent germinal centers.

Question 31

What is the function of gut microbes in immunity?

Answer 31

harmless but are non-self; induce immune response; oral antigens introduced via ingestion.

Question 32

What is a germinal center?

Answer 32

An anatomically restricted site where B cells mutate and are selected to generate high-affinity antibodies.

Question 33

What are tonsils and their arrangement?

Answer 33

Pharyngeal, tubal, palatine, and lingual tonsils; form the Waldeyer ring encircling the oral and nasal cavity.

Question 34

How are secondary lymphoid organs (SLOs) connected?

Answer 34

Connected via circulation and lymphatics; lymphocytes circulate through blood and lymph.

Question 35

How often do naïve T cells recirculate?

Answer 35

Approximately every 24 hours.

Question 36

What is extravasation of naïve T cells?

Answer 36

The process by which naïve T cells enter lymph nodes from circulation.

Question 37

How are antigens presented to T cells?

Answer 37

Peptides are displayed in MHC I/II proteins; T cell receptors (TCRs) bind to these complexes.

Question 38

What are dendritic cells and their role?

Answer 38

Antigen-presenting cells; include migrating tissue-resident varieties; migrate via afferent lymph to lymph nodes.