1 / 24

Lymphoid Tissues and Organs:

Lymphoid Tissues and Organs: . - Leukocytes may be distributed in the body as: 1- Single cells in tissues and circulation. 2- Lymphoid accumulations (Peyer’s patches). 3- Aggregations within Lymphoid organs; Primary and secondary lymphoid organs.

xaria
Télécharger la présentation

Lymphoid Tissues and Organs:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Lymphoid Tissues and Organs: - Leukocytes may be distributed in the body as: 1-Singlecells in tissues and circulation. 2-Lymphoid accumulations(Peyer’s patches). 3-Aggregations within Lymphoid organs; Primary and secondary lymphoid organs. -Primary Lymphoid Organs: Thymus and Bone marrow. -Secondary Lymphoid Organs: Spleen, Lymph nodes, Tonsils, and MALT.

  2. Primary and Secondary Lymphoid Organs: N

  3. N Primary lymphoid organs: 1- Thymus: -T Lymphocytes develop within this lymphoid organ. -Function: The clonal selection of T lymphocytes. (Lymphocyte educational Center) -It increases in size during fetal and neonatal life. -It is progressively inactivated (curved spirally) following puberty. -Two important parts: 1-Thymic Cortex. 2-Thymic Medulla.

  4. Primary lymphoid organs: The Thymus and its parts. The thymus diagram : Parts and location.

  5. N 2-Bone marrow: -B lymphocytes are “home schooled” within this organs. -Function: Primary differentiation of B lymphocytes. B lymphocytes begin to display IgM on their surfaces. -The primary site for cytokines-Immune cell interactions. -Bone marrow removes the B cells that show self- reactivity by apoptosis.

  6. Secondary Lymphoid Organs: -Secondary lymphoid organs function as filtration devices removing foreign matter, dead cells, and microbial toxins from the circulation. -Blood vessels and lymphatic vessels richly supply these organs. -Specialized regions of the vasculature (endothelial venules) facilitate movement of immune cells between blood and the tissues of these organs. -The leukocyte-rich nature stimulate cellular interaction.

  7. N Secondary Lymphoid Organs: 1-Lymph nodes: -It acts as filters to purify lymph. -Divided into the cortex and medulla. -The superficial cortex contains lymphocyte-rich nodules (follicles) (mainly B cells). -The deep cortex is the T-cell-rich area.

  8. N 2-The Spleen: -The largest lymphoid organ. -Concentrates blood-borne antigens and microbes. -Contains T cells, B cells, and Large numbers of plasma cells (secreting immunoglobulins into the circulation). -Divided into: 1-Lymphocyte-rich white pulp. 2-Erythrocyte-rich red pulp (also contains macrophages).

  9. N 3-Mucosa-associated lymphoid tissues(MALT): -Other sites for immune-cells interaction. -Tonsils in the nasopharynx. -Peyer’s patches in the sub-mucosal surfaces of small intestine. The Lymphatic circulatory system: -Leukocytes and their products use two circulatory systems: 1-Cardiovascular system. 2-Lymphatic circulatory system. (Textbook : Page 85-86).

  10. Lymphocyte Development: -Stem cells of bone marrow (prothymocytes; negative for CD4,CD8, and TCR) migrate via the circulation to the thymic cortex. -The newly arrived thymocytes acquire CD4,8, and TCR (Positive cells) -Cortical thymocytesare selected by their interaction to cortical epithelial cells (positive selection). -Medullary thymocytesare selected (negative selection). -Mature T cells are released into the circulation.

  11. Maturation of T lymphocytes in Thymus: N

  12. Lymphocyte Activation: Lymphocyte activation occurs according to following consequences: 1-Antigen endocytosis and processing. 2-Antigen presentation. -Extracellular microbes and toxins are engulfed by endocytosis.(Endocytic pathway). -Intracellular microbes (viruses) are processed by cytolytic pathway.

  13. N Endocytosis of extracellular microbes: 1-Phagocytosis 2-Receptor-mediated endocytosis. 3-Pinocytosis.

  14. Antigen presentation by MHC Class II: -Endocytic vesicles (phagosomes; derived from phagocytosis) fuse with lysosomes. -Phagolysosome interacts with endoplasmic reticulum vesicles. -The digested peptides carried by MHC II to cell surface.

  15. Antigen presentation by MHC Class I: -Cytoplasmic protein-ubiquitin reaction. -Proteasome action on the complex. -Fusion of processed peptide with E.R vesicle which carry MHC Class I to the cell surface.

  16. Activation of T Lymphocytes: -MHC II-epitope-Complex interaction with TCR. -B7(CD80/86) Co-stimulatory interaction with CD28. -IL-2 production from activated T cell. -Overexpression of IL-2R on T cell surface.

  17. N -In the presence of IL-12, native CD4 lymphocyte is differentiated as a CD4 Th1. Activation of CD8 (Tc) cell by effector Th1:

  18. N Activation of B Lymphocytes by effector Th2: -MHC II-epitope-Complex interaction with TCR. -CD40-CD40 Ligand interaction. -Antibody-epitope interaction.

  19. Lymphocyte Effector Functions: Cell-mediated immunity: 1-Role of CD4 T cells in Delayed (- type) hypersensitivity:

  20. N 2-Role of CD8 T cell: T cell Cytotoxicity : A-Target cell recognition. B-Target cell destruction: -Perforins and Granzymeseffect.

  21. N 3-Role of NK cells in cellular immunity:

  22. N Humoral immunity: 1-Agglutination of invaders. 2-Neutralization (virus, toxins). 3-Opsonization. 4-Complement activation. 5-ADCC: NK cell and Eosinophils. 6-Immediate hypersensitivity.

  23. Humoral immunity and effector lymphocyte function: N

  24. The ADCC Mechanism: N

More Related