Immune System Notes

Innate Immunity

• Rapid, immediate response.
• Not specific to a particular pathogen.
• Short lasting (less than 7 days).
• No memory.
• Four parts: Barrier, Sensing, Communication, Destruction.

Barriers

• Skin and mucus trap pathogens.

Sensing

• Antigen Presenting Cells (APCs): Macrophages and Dendritic cells.
• APCs express Pattern Recognition Receptors (PRR) that bind to common ligands on many pathogens.
• APCs engulf and destroy pathogens, and secrete cytokines.

Communication

• Cytokines produced by macrophages and dendritic cells.
• Mediate inflammation, fever, and attract other immune cells.
• Histamines stimulate mucus production.

Destroy

• Recruited immune cells destroy infected cells and pathogens.

Adaptive Immunity

• Slower response.
• Specific to pathogen-specific antibodies.
• Has memory; second response is faster and stronger.

Key Components

• Antigen presentation.
• T helper cells & cytotoxic T cells.
• Plasma B cells produce antibodies.
• Memory B cells.

Antigen Presentation

• Dendritic cells present digested pathogen pieces (antigens) to T cells.
• MHC (major histocompatibility complex) presents antigen to TCR (T cell receptor).
• Co-stimulation is required for T cell activation (two signals needed).

B Cell Activation

• Requires signals from APC and activated T helper cell.
• Activated B cells differentiate into plasma cells, which produce specific antibodies.
• Antibody binds to the epitope on the antigen.

Memory

• Activated B cells proliferate and differentiate into plasma and memory cells.
• Memory B cells provide a faster and stronger response upon second exposure to the same antigen.

Vaccines

• Designed to provide an accelerated and stronger adaptive immune response to a specific pathogen.

Immune Receptors

• Often bind cell surface proteins as ligands and are used for co-stimulation.
• Signal transduction overlaps with other types of signaling.