Cells andf Tissues of the Immune System

MICRO:3164

What happens in the secondary lymphoid tissues?

Sites where the immune cells are activated

What two organs are secondary lymphoid tissues?

• Spleen

• Lymph Nodes

What happens in the primary lymphoid tissues?

Cells are produced and mature

What organs are primary lymphoid tissues?

• Bone marrow

• Thymus

What is Hematopoiesis?

The production of RBCs and WBCs in the bone marrow

What specifically happens in the thymus?

T cells mature and get tested for quality control

What are lymph nodes?

The activation site for T and B cells

What is the purpose of the spleen?

To remove aging and damaged blood cells from circulation

What causes the immune cells in the spleen to be activated?

If pathogens are detected in the blood, to prevent sepsis

What are examples of major protein components of the immune system?

• Receptors

• Antimicrobial peptides and proteins

• Antibodies

• Cytokines

• Chemokines

What is an AMP?

Play important role in killing microbes

• examples:

• Defensins

• Lysozyme

What do defensins do?

Form pores that destroy the pathogen

What do lysozymes do?

Break bonds in the peptidoglycan wall of bacteria

What are antibodies produced by?

B cells

What are the three things antibodies do to fight pathogens?

• Neutralization - makes them unable to bind

• Opsonization - ez to eat

• Complement activation

Cytokines

• Important for communication between immune cells

• Act as migration signals for immune cells and attract them to sites of infection/tissue damage

What is hematopoiesis?

Blood cell production

• RBC and immune cells are made in the bone marrow

What cells are phagocytes?

• Neutrophils

• Macrophages

• Dendritic cells

What are granulocytes?

Contain cytoplasmic granules filled with antimicrobial proteins

• the granules get release upon activation via exocytosis

• Neutrophil

Antigen

A substance that stimulates an immune response

What are major antigen presenting cells?

• Macrophages

• Dendritic cells

Both play a role in activating the adaptive immune system

Antigen Presentation steps

• Phagocytosis of bacteria via APC

• Digestion of microbe into antigens

• Presentation of antigens to T cell to activate them

Mast cells

Found in skin.mucous membranes

• act as sentinel cells

• express proteins that attract other immune cells to sites of infection

Neutrophils

Most abundant in blood: 50-75% of leukocytes

• short lived

• First responders to infection/inflammation

• Has AMPS

• phagocyte

What is NETosis in neutrophils?

A released net to trap bacteria

• bacteria use DNase to escape NETs

Natural Killer Cells

Specialized immune cells that kill infected/cancerous cells

• pumps out granzyme to infected cell

• granzyme punches hole in infected cell killing it

Macrophages

Reside in all tissues

• act as sentinel cells

• phagocytes

• performs antigen presentation

Dendritic Cell

Circulate in blood

• Infiltrate tissue in response to inflammation signals

• Important role in activating other immune cells

• Performs antigen presentation

• Travels from tissue to lymph nodes to activate other immune cells

B cells and T cells are apart of what?

The adaptive immune system

• must be activated via antigen presenting cells in the lymph nodes/spleen

• also known as lypmhocytes

Do B/T cells have the same receptors?

No they are unique!

• one they are presented their specific antigen its then activated and ready to fight infection

Where are B cells generated and mature?

In the bone marrow

• both mature and generated

What does a B cell turn into after it is activated?

• Memory B cell

• Plasma cells - (produce antibodies)

Where do T cells generate and mature in?

They are generated in the bone marrow but mature in the thymus

How are the two major T cell subsets defined and what are they?

They are defined by their co-receptors

• CD8 T cells - cytotoxic T cells

• CD4 T cells - helper T cells