Innate Immunity

Also known as non-specific immunity
First line of defense against infection
Provides immediate response to pathogens
Mechanisms:
- Barrier function (skin and mucous membranes)
- Phagocytosis (engulfing and digesting foreign particles)
- Inflammation (response to tissue damage)
- Complement system (group of proteins that work together to help eliminate pathogens)
Cells involved:
- Neutrophils
- Macrophages
- Dendritic cells
- Natural killer cells

Process by which cells display antigens to T cells
Cells involved:
- Antigen-presenting cells (APCs): dendritic cells, macrophages, and B cells
- T cells: CD4+ (helper) and CD8+ (cytotoxic)
Mechanisms:
- Phagocytosis and processing of antigens by APCs
- Display of antigens on surface of APCs using major histocompatibility complex (MHC) molecules
- Recognition of antigens by T cells using T cell receptors (TCRs)

Also known as specific immunity
Provides long-term protection against specific pathogens
Mechanisms:
- Cell-mediated immunity (T cells): provides direct killing of infected cells
- Humoral immunity (B cells and antibodies): provides indirect killing of pathogens
Cells involved:
- T cells: CD4+ (helper) and CD8+ (cytotoxic)
- B cells: produce antibodies in response to antigens
Activation of adaptive immunity:
- Recognition of antigens by T cells
- Activation of B cells by T cells and antigens
- Production of antibodies and immune response

Provides immediate response to pathogens, first line of defense against infection
Mechanisms include: • Barrier function (skin and mucous membranes prevent entry of pathogens) • Phagocytosis (engulfing and digesting foreign particles using neutrophils and macrophages) • Inflammation (response to tissue damage, increased blood flow, and swelling) • Complement system (group of proteins that work together to help eliminate pathogens)
Cells involved: neutrophils, macrophages, dendritic cells, and natural killer cells

Proteins produced by B cells in response to antigens
Function: bind to specific antigens, marking them for destruction
Classes: • IgA (found in mucous membranes, provides protection against infection) • IgD (found on surface of mature B cells, helps activate immune response) • IgE (involved in allergic reactions) • IgG (most common, provides long-term immunity) • IgM (first antibody produced in response to infection, provides immediate protection)

Process by which cells display antigens to T cells
Cells involved: antigen-presenting cells (APCs) and T cells
Mechanisms: • Phagocytosis and processing of antigens by APCs (dendritic cells, macrophages, and B cells) • Display of antigens on surface of APCs using major histocompatibility complex (MHC) molecules • Recognition of antigens by T cells using T cell receptors (TCRs)

Provides long-term protection against specific pathogens
Mechanisms: • Cell-mediated immunity (T cells): provides direct killing of infected cells • Humoral immunity (B cells and antibodies): provides indirect killing of pathogens
Cells involved: T cells (CD4+ and CD8+), B cells (produce antibodies in response to antigens)
Activation of adaptive immunity: • Recognition of antigens by T cells • Activation of B cells by T cells and antigens • Production of antibodies and immune response

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