L1: Cells and Tissues

where are all immune cells derived from

haematopoietic stem cells in bone marrow

what are 2 key properties of haematopoietic stem cells

self-renewal and multipotency

what controls proliferation and differentiation of immune cells

growth factors

what are the 2 main developmental lineages

myeloid (innate immunity) and lymphoid (adaptive immunity)

approximately how many immune cells are in the body

~10^12-13

is the immune system static or dynamic

dynamic - constantly changing and adaptable nature of responses

what does moveable mean in immune context

cells circulate between blood, tissues and lymphatics

what are the three types of granulocytes

neutrophils, eosinophils and basophils

what is the most abundant circulating wbc

neutrophil

what is the main function of neutrophils

phagocytosis and rapid killing of phagocytes

are neutrophils short lived or long lived

short lived

when are neutrophils recruited

during inflammation

what is produced in neutrophil phagolysosomes to kill microbes

reactive oxygen species (H2O2, HOCl)

what are the first responders

neutrophils NOT macrophages

what do eosinophil granules contain

arginine-rich basic proteins

what do eosinophils mainly kill

parasites esp worms

what do mast cells granules contain

histamine and heparin

where are mast cells found

tissues

where are basophils found

circulation

what is main role of basophils and mast cells

inflammatioj

what do monocytes differentiate into

macrophages

what is the main function of macrophages

phagocytosis

are macrophages short lived or long lived

long lived

what is a key role of macrophages besides killing pathogens

clearing dead cells/debris

what percentage of circulating leukocytes are lymphocytes

~25%

what percentage of total lymphocytes are found in blood

~2% - most are not in blood

where do t cells develop

thymus

where do b cells develop

bone marrow

are lymphocytes short or long lived

long lived

what is the main role of lymphocytes

adaptive immunity

what type of cells are NK cells

large granular lymphocytes

what do NK cells kill

virus-infected cells and tumour cells

what molecules do NK cells use to kill

perforin and granzymes

which immunity are NK cells found

innate not adaptive

what are the primary lymphoid organs

bone marrow and thymus

what happens in primary lymphoid organs

development of lymphocytes

what are secondary lymphoid organs

lymph nodes, spleen, mucosa-associated lymphoid tissue (MALT - nose, lungs)

where do t cells get activated in lymph nodes

paracortex

where do b cells get activated

germinal centres

how do lymphocytes enter lymph nodes

HEV - high endothelial venules

what controls lymphocyte trafficiking

homing receptors

what is the main function of dendritic cells

activate t cells

where do immature dendritic cells reside

peripheral tissue

what do immature dendritic cells do

capture antigens

what happens after activation

migrate to lymph nodes

how is antigen uptake in immature DC

high

how is antigen presentation in mature DC

high

what do mature dendritic cells do

present antigens

how do antigen and lymphocytes meets

1. DC capture antigen in tissues

2. they travel via lymphatics

3. present the antigens in lymph nodes to T cells

what is G-CSF used for

stimulating stem cells to increase production of immune cells

what is haemostasis

process of stopping bleeding using platelets

what is a plasma cells

a b cell that produces and secretes antibodies not found in the blood but in the lymph nodes and spleen