Unit 4: Circulatory System (Leukocytes)

Monocytes

• dendritic cells (both innate and acquired)

• macrophages (innate)

granulocytes

neutrophils, eosinophils, basophils

• always innate immunity

Lymphocytes

• B Cells (Acquired)

• T Cells (Acquired)

• NK Cells (Innate)

Neutrophils

• first responders (very common butt dies in large numbers)

• phagocytize bacteria and fungi and promote inflammation 

• release toxic substances stored in granules to kill pathogens

eosinophil

• kill parasitic worms by releasing toxic substances stored in their granules

• regulate inflammation by deactivating histamine

basophils

• help fight infections and allergies by releasing chemicals such as histamine and cytokines (chemicals help regulate inflammatory response)

• release heparin to prevent blood clotting

macrophages

• garbage collectors

• phagocytize pathogens, dead cells, and other debris

• release cytokines to recruit other immune cells at the site of damage

dendritic cells

• form bridge between innate and adaptive immune response by presenting antigens to lymphocytes

• patrol tissues for pathogens or abnormal cells and then migrate to lymph nodes to activate specific lymphocytes

• primary APC

B Cells

• produce antibodies to fight infection and neutralize pathogens

• act as APCs to activate other immune cells like T cells

• form memory cells for a faster response to future infections

T Cells

• destory infected or cancerous cells by releasing cytotoxins, direct other immune cells through cytokine signals, and regulate the immune response to prevent autoimmune disease

• form memory cells for a faster response to future infections

• only WBC using antigen presentation

NK Cells

• release enzymes and toxins to kill cancer/virus infected cells 

• kill target cells immediately, without needing to be pre-activated by other immune cells

Prevalence of Leukocytes

Never Let Monkeys Eat Bananas

• Neutrophils (most prevalent)

• Lymphocytes

• Macrophages/dendritic cells

• Eosinophils

• Basophils (least prevalent)

Antigen Presenting Cell (APC)

• dendritic cells, macrophages, and B cells

diapedesis

squeezing of WBCs through capillary walls

chemotaxis

movement of cells towards where chemical signal is most concentrated