Lecture 1 - cells and tissue of immune system

what are the branches of immune system

Innate and adaptive immune system

The 3 Rs of immunity

Recognition

Response

Regulation

What do Immune cells have that help them detect their surroundings?

Thousands of receptors, transmit signals from cell surface to nucleus

What are Cytokines

• Soluble messengers that allow cells to communicate (not just for immune cells

• made from activated immune cells, epithelial cells and stroma cells

What are the different types of Cytokines ?

• Interleukins → communication between immune cells

• Interferons → intefere viral infection

• Tumour necrosis factors (TNFs)→ cause tumour necrosis

• Colony stimulating factors ( CSFs) → stimulate cell growth

• Chemokines → allow cell movement

What are the different ways cytokines can behave?

• Pleitropy → same cytokine, differnet effect on different cells

• Redundancy → different cytokine, same effect

• Synergy → have amplified effect on cell

• Anagonism → opposite effects

What do immune cells originate from

all orginate in bone marrow

Hematopoietic stem cells → hematopoitic porgenirator cells → Mature Hematopoietic cells

Why doesn’t immune response happen in circulation?

Immune cells must stop at their target cell in order to initiate a response, in circulation blood is constantly moving

Geography of immune cells

All originate in bone marrow, once differntiated enter circulation where can:

• enter lymphoid organs through High endothelial venules, then leave to entre lymphatics (where it connects to tissue)

• From blood can also enter peripheral tissue through capillaries or venous to act as first line of defence then can drain into lyphatics through lymphatic endotehlial cells

What are the different lymphoidal organs

Primary lyphoidal organs, where immune cells made/originate → bone marrow and thymus

Secondary lymphoidal organs, where immune cells have a repsonce → spleen, lymph nodes

What are the types of graulocytes

• immune cells that contain granules :

Neutrophils

Eosiphils

Basophils / mast cells

Neutrophils

• major circulting white blood cell

• short lived

• no inflammation just die

• if inflammation they are recruited from blood into tissue, attach to blood vessles

• good at phagocytosis, engulf things and have lots of toxic things in granules

• different granules release toxic things

• no damage to surroudning tissue as toxins released inside neutraphil

• funny shaped nucleus

Esinophils

• contain granules but with different things inside, contain arganine rich proteins

• Mostly in tissue, only few cirulating

• reslease highly toxic granules killing paracytes and bacteria that cannot be phagocytosed

• release cytokines and prostaglandins inportant for innflamation IL-3, IL-5,IL-8

Mast cells (and basophils)

Mast cells in tissue, they degranulate (herparin , histomines), important in inflammation - they recognise something is wrong and start immune response/ inflammation , sentinal cells

Basophils in circulation

Macrophages

• importnat in engulfing bacteria

• very long lived

• found in tissue

• precursor monocyte in circulation → enter tissue become macrophage

• Many made before birth e.g in feital liver Kuppfer cells

• also have important role in cleaning up debri

Lymphocytes

• no granules, just nucleus

• make up 25% of white blood cells (leukocytes)

• major cell of adaptive immune system

• live very long

• Various stages of differntatition and behave differently ar different stages ; resting, activates, plamsa cells (only make antibodies, type of B cell), niave (e.g. T cell never seen antigen/ exposed to antigen ), memory

• 3 types of Lymphocytes:

B cells

• originate in bone marrow

• recognises antigen diffrentatied into plasma cell and then create antibodies , becomes memory B cell

• antibody- meditated immunity

T cells

• develop in bone marrow then into thymus matures

• cell mediated immunity

• activate B cells and other cells

• different types of T cells; CD4+ (HELPER T cell), CD8 (cytotoxic T cell)

Natural Killer cells (NK cells)

• Important in Innate immune response

• large garnular lymphocytes

• kill cells that have been infected by virus NOT VIRUS ITSELF

• release garnules containing perforin, granzymes to kill cells

• secreate IFN-gamma

Lymph node structure

like a sac, all blood passively drains through lymph comes in through afferent end and leaves through efferent end

have T cells in paracorex and B cells in cortex in follicles within germinal center

Dendritic cells

• main bridge between innate and adaptive immunity

• they are an APC

• come form bone marrow, enter blood and then travel to organ where they take residance in e.g. skin

• once they encounter an antigen they take up antigen then change conformation/phenotype and then leaves tissue through lyphatics and then goes to lymph nodes

what happens when dentritic cells get into lymph nodes

• In lymph nodes have niave T cells ciruclation to match with a DC

• T cells enter lyphoid organ from blood through High endothelial venolue

• if T cell matches with DC then become effector T cell where will then enter blood and then site of tissue infection

Cells of innate and adaptive immune system