cells and organs of the immune system

The formation and development of red and white blood cells from stem cells within the bone marrow. Facilitated by stromal cells

Hematopoiesis

Provide a hematopoietic inducing microenvironment in the bone marrow

Stromal cells

Either the myeloid or lymphoid lineage progenitors. Once differentiated into one of these precursors the stem cell can no longer self-renew and must form a cell that lays within that lineage

Hematopoietic stem cells can differentiate into

• WBC’s types:

• Monocytes

• Lymphocytes

• Basophils

• Eosinophils

• Neutrophils

Leukocytes

• T cells

• B cells

• Natural killer cells

• Dendritic cells

The lymphoid progenitor can differentiate to form

Red blood cells

Erythrocytes

Platelet generating cells

Megakaryocytes

• granulocyte WBC’s (BEN)

• Erythrocytes

• Megakaryocytes

• Dendritic cells

The myeloid progenitor can differentiate to form

Lymphoid cells, as they have antigen recognition (B, T, and NK cells)

The key cells of adaptive immunity

• membrane bound antibodies/immunoglobulin

• About 150,000 antibodies per cell

• Binding to antigen activates cell causing rapid division

B lymphocytes

Plasma cells

• secrete antibodies which can stick to pathogens for recognition

Or memory cells

• long lived

• Contains the same antibodies as the parent cell

After activation B cells can differentiate into

• contains T cell receptors which recognize specific antigens ( on MHC cells)

• Only interact with MHC cells which are antigen presenting

• Presentation activates the cell causing proliferation and differentiation

T lymphocytes

T helper cells

• go on to activate other immune cells

• Can differentiate into memory cells

T cytotoxic cells

T lymphocytes differentiate into

• cytotoxic activity to kill infected/tumor cells using chemicals

• No antigen specific receptors (innate)

• Kill through identifying abnormal cell surfaces and antibodies bound to pathogen surfaces

Natural killer cells

• have T cell receptors for antigen recognition

• Recognize lipid and Glycolipid antigens

• Secrete cytokines to stimulate B and T cells

Natural killer T cells

• both types of mononucular phagocytes

• Monocytes are only found in the blood, turn into macrophages which are only in the tissues

• Macrophages are bigger, more complex and more hydrolytic

Monocyte vs macrophages

• repair and remodel: by engulfing pathogens

• Present pathogens: by engulfing then presenting to t-cells for activation

• Destroy pathogens: use pseudopodia to attach to pathogen for phagocytosis

Macrophage function

• multilobe nucleus and granulated

• Phagocyte

• Defends against various pathogens

• Most abundant and fastest to respond to area of infection which causes inflammation

Neutrophils

• bilobed nucleus and granulated

• Phagocyte

• Parasites

Eosinophils

• lobed nucleus and most granulated

• Not phagocytic

• Allergic response (due to specific chemicals released Ex. Histamine)

Basophils

• many types & functions

• Use processes to attach to pathogen and phagocytize antigen in one area and present in another area away from infection

• Involved in development and maturation of other cells (B cells)

Dendritic cells

• bone marrow and thymus

• Areas of development and maturation

Primary lymphoid organs

• the lymphatic system: including nodes, spleen and MALT

• Trap antigens for mature lymphocytes to interact with antigens for activation

• Clonal expansion and differentiation into effector cells

Secondary lymphoid organs

The lymphatic system ducts remove excess extracellular fluids and toxic substances from tissues. In this system these fluids are ‘tested’ by immune cells in the lymph nodes to check for pathogens

What does the lymphatic system do to maintain immunity

Blood vessels and lymphatic system

How are primary and secondary lymphoid organs connected