MICR2000 MOdule 7 L3: Innate Immune System

What are the main types of phagocytes?

Neutrophils, macrophages, and dendritic cells.

What are the main steps of phagocytosis?

Recognition → Engulfment → Phagosome formation → Fusion with lysosome → Killing & degradation.

What is opsonisation?

Coating of microbes with complement proteins or antibodies to enhance phagocytosis.

Which receptors recognise opsonised microbes?

Fc receptors (antibodies) and complement receptors (complement proteins).

Name two major ways phagocytes kill microbes.

Enzymatic degradation and reactive oxygen/nitrogen species.

What are phagocytes

macrophages, neutrophils and dendritic cells

What is the main function of neutrophils?v

Rapidly migrate to infection sites, phagocytose, and kill microbes.

What are neutrophil NETs?

DNA and antibacterial proteins released by dying neutrophils that trap pathogens.

What is the relationship between monocytes and macrophages?

Monocytes circulate in blood; macrophages are tissue-resident and derived from monocytes.

What do macrophages release to recruit and activate other cells?

Cytokines and chemokines.

What is the key function of dendritic cells (DCs)?

Capture antigen and present it to T cells to initiate adaptive immunity.

difference between monocytes and macrophages

macrophages are present in the tissue whilst monocytes are present in the blood

What activates dendritic cells to mature and migrate?

Pathogen products (PAMPs).

What do NK cells target and how?

They are lymphocytes like T and B Cells. they directly kill virally infected cells and tumour cells. they detect changes at chemical level of cell surfaces

What is the complement system?

A cascade of ~30 serum proteins that enhance pathogen destruction.

Name the three complement activation pathways.

Classical (antibody), Mannose-binding lectin, and Alternative (direct recognition).

What triggers inflammation?

Cell damage or pathogen recognition.

What is extravasation?

Step in inflammation: Movement of immune cells from blood vessels into infected tissue. - involves changes in protein on endothelium of blood vessels so immune cells can slip thrhough

What is chemotaxis?

Step in inflammation: Directed movement of immune cells up a chemical gradient toward infection.

what are PAMPs

pathogen associated molecular pattern - characteristic molecuels conserved across classes of pathogens 

What are PRRs and what do they do?

Pattern recognition receptors; they detect PAMPs and trigger immune activation.

What are Toll-like receptors (TLRs)?

A family of PRRs that recognise specific pathogen molecules.

What happens when PAMPs activate TLRs?

Cytokine release, enhanced microbial killing, dendritic cell maturation.

What are toll like receptors (TLR)

Type of pattern recognition receptor found on innate immune cells. some are on cell surfaces (detect cell wall components) whilst others are intracellular (detect viral proteins and dna etc.)