Immune System, Organs

Question 1

Immune system

Answer 1

Immune system:
- system of lymphoid organs in which lymphoid cells
		○ proliferate (divide)
		○ differentiate (mature)
- composed of capsulated organs
- diffuse accumulation of lymphoid tissue
- located in the whole body
- functions in a coordinate manner

Question 2

two groups of lymphoid organs

Answer 2

1. Primary (central) lymphoid organs: production, proliferation and differentiation of lymphoid cells without presence of any Ag (Ag-independent)
   - all Lymphocytes leaving the central lymphoid organs are naive (virgin) Lymphocytes - they have never met an antigen
   - once they meet antigen, the proliferate and are differentiated into effector Lymphocytes
2. Seconday lymphoid organs:
   - place where lymphocytes become effector lymphocytes
   - where the specific, adaptive immune response towards the Ag is generated

Question 3

Lymphoid cells produces

Answer 3

Lymphoid cells continuously recirculate between blood and lymph and produce:

• antibodies
• receptors
• soluble mediators (lymphokines)
• Lymph (extracellular fluid )

Question 4

Bone marrow

Answer 4

Bone marrow

• basic lymphoid organ
• hematopoesis: produces all types of blood cells and immune cells

(- during embryonic development the Yolk sac and the fetal liver produce blood cells, when those cells are destroyed afterbirth the baby turns yellow because of bilirubin (product of hemoglobin))

Question 5

Lymph

Answer 5

• small gland located behind sternum
• composed of migrating bone-marrow lymphoid stem cells and nonlymphoid cells which constantly interact
  • T- lymphocytes are produced in bone marrow
  • Thymus is “school” for T-lymphocytes, learn how to discriminate between self and foreign molecules
  • only perfect t-lymhocytes (2 %) are released
• structure and function diminishes (involution) after
  teenage age

Question 6

Lymph nodes

Answer 6

• secondary lymphoid organ

- immune response against Antigens residing in tissue

Question 7

Spleen

Answer 7

• against Antigens in blood

red pulp
- eliminates defective or orld Er and Tr, reservoir of blood cells for emergencies

white pulp
- lymphoid tissue, related to humoral immunity

function of both: physiological immunity

Question 8

MALT

- intestinal MALT

Answer 8

against antigens in mucosa

uncapsulated accummulations of lymphoid tissue
- includes tonsils, appendix, nasal-ALT, broncho-alveolar lymphoid tissue, in the intestines, in the urinary tract

intestinal MALT:

• mainly B-Lymphocytes
• Antigens penetrate through specialized epithelium composed of M-cells