1. Vinnytsya National Pirogov Memorial University Histology Department
Hematopoietic organs and organs of immune responce
as. Hrytsenko A.S.

2. HEMATOPOIETIC ORGANS AND ORGANS OF IMMUNE RESPONCE
Functions of the Hematopoietic organs
The maintenance of immunological homeostasis and morphological composition of blood.
Central organs:
1) formation of all types of blood cells;
2) antigen-independent (without the presence of antigens) formation and differentiation of lymphocytes.
Peripheral organs:
1) antigen-dependent (under the influence of antigens) differentiation of effector cells (T and B lymphocytes);
2) elimination (destruction) of blood cells that have completed their life cycle;
3) depositing of blood;
4) cleaning of blood and lymph from foreign particles, bacteria, remains of dead cells.

3. Parenchyma – elements that make the specific functions of the organ.
Stroma – from the Greek “Stroma” – mat for sitting or lying. Stroma – supporting tissue For Hemopoietic organs – reticular tissue. For Thymus – epithelioreticular tissue.
Parenchyma – elements that make the specific functions of the organ.

4. Red bone marrow
Functions: physiological regeneration of blood cells: red blood cells, granular leukocytes, monocytes, platelets, B-lymphocytes and precursors of T-lymphocytes;
removal of old and defective blood cells from the blood flow and their phagocytosis by macrophages of the stroma

5. Parenchyma –hematopoietic islands:
Red bone marrow
Stroma
Hard stroma - osteoblasts of bone endosteum;
Soft stroma –
reticular cells and fibers; endothelial cells of sinusoidal capillaries;
adventitial cells;
macrophages;
adipose cells (50% of volume)
Parenchyma –hematopoietic islands:
erythroblastic;
myeloblastic;
lymphoblastic;
monoblastic;
megacarioblastic.

6. In the adult, when the rate of blood cell formation has diminished, the tissue in the medullary cavity consists mostly of fat cells; it is then called yellow marrow. Under appropriate stimuli; such as extreme blood loss, the yellow marrow can revert to red marrow.

7. Functions of the thymus :
Antigen-independent differentiation of lymphocytes.
Proliferation, antigen-independent differentiation and migration of T-lymphocytes.
Secretion of biologically active factors that regulate immunopoiesis (thymosin, thymolin, thymopoetin).

8. Thymus Stroma - epitelioreticular cells.
1. Secretory (cortical, cortical-medullar).
2. “Cells-tenders”.
3. Cells of Hassall’s corpuscles
Parenchyma – thymus lymphoid elements:
1. Subcapsular (3-5%) precursors of T-lymphocytes (from RBM).
2. Cortical (85 – 90%) thymocytes.
3. Medullar (10-15%) thymocytes.
Macrophages, dendritic cells, fibroblasts, tissue basophils.

9. Blood thymic barrier Function: prevention of the contact between the high concentrations of antigens circulating in the blood and the developing immature lymphocytes in the thymic cortex Structure:
Endotelium
Basement membrane of endothelial cells
Thin perivascular connective tissue space (containing many, pericytes, macrophages, fibroblasts)
Basement membrane of epithelioreticular cells
Epithelioreticular cells

10. AGE INVOLUTION OF THE THYMUS
Phases: fast to 10 years;
slow to 25 years;
fast to 40 years;
slow.
Elements of connective tissue are replaced by adipose tissue;
The number of collagen fibers increases;
The number of thymocytes reduced.

11. Accidental thymus involution
Reasons: intoxication, starvation, chronic stress conditions, acute stress, insomnia, infectious disease, physical exhaustion.
Reducing the cortex area;
Reducing the number of thymocytes;
Increasing the medulla area;
Increasing the number of epithelial-reticulocytes;
Increasing the number and size of thymic corpuscles.

12. Peripheral hematopoietic organs
1. Have mesenchymal origin.
2. Contein immunocompetent cells.
3. Antigen-dependent differentiation of lymphocytes takes place here.
4. Contain lymphoid nodules with the germinal centers of proliferation.

13. Spleen Functions Immune functions : -proliferation of lymphocytes
-production of humoral antibodies
-removal of macromolecular antigen from the blood
Hematopoietic functions :
-formation of blood cells during fetal life
-removal and destruction of senile, damaged and abnormal red blood cells and platelets
-retrieval of the iron from red cell hemoglobin
-storage of blood, especially red blood cells, in some species

14. Structure of the spleen
White pulp(20%)
Red pulp(80%)
Reticular stroma that contains that contains next parenchimatous elements :
Red blood cells, white blood cells, lymphocytes.
Large number of macrophages.
Plasma cells.
Vascular system of sinuses.
Reticular stroma that contains next parenchimatous elements - lymphocytes, monocytes, plasma cells and macrophages, which are forming :
1. Periarterial lymphatic sheath.
2. Lymphoid nodules.
3. Ellipsoids.

15. Periarterial lymphoid sheath
2-4 layers of small lymphocytes surrounding the pulp artery.
Interdigital cells.
From outside - marginal zone: macrophages, lymphocytes, monocytes, eosinophils, single plasma cells.
Т-dependent zone.

16. Lymphoid nodules Situated at the place of arteries branching.
Periarterial zone (small lymphocytes, interdigital cells).
Mantle zone (compact situated B-lymphocytes).
Marginal zone (T- and B-lymphocytes, macrophages).
Germinal (light) center (B-lymphoblasts, macrophages, dendritic cells) - center B-lymphocytes proliferation. В –zone.

17. Lymph node
STROMA
Reticular connective tissue - net of reticular cells and fibers, macrophages, antigen presenting cells (APC)
PARENCHYMA
Lymphoid tissue :
Cortex - lymphoid nodules (В-zone).
Medullar (В –zone).
Paracortical zone (Т-zone)

18. Conteins lymphatic nodules ( В-zone)
Lymph node
Cortex
Conteins lymphatic nodules ( В-zone)
From outside – reticular-endoteliocytes, fixed macrophages.
Germinative center (center of proliferation) – lymphoblasts, macrophages, dendrite cells, lymphocytes (mostly В-lymphocytes).

19. Paracortical zone Contains mostly Т-lymphocytes.
Supporting cells – «interdigital cells» - macrophages that lost ability for phagocytosis and produce humoral factors of lymphogenesis

20. Medullar Medullar cords Reticular tissue В-lymphocytes Plasma cells
Macrophages

21. Subcapsular (marginal) Perinodullar Medullar Hilum sinus
Sinuses of lymph node
Spaces between the capsule and trabeculae, on the one hand, and spaces between medullar nodules and cords – on the other.
Subcapsular (marginal)
Perinodullar
Medullar
Hilum sinus