CH 24: Innate and Adaptive Immune Systems

Flashcards covering key vocabulary and concepts from the lecture notes on the innate and adaptive immune systems.

Activating Proteins

These are proteins found on the surface of cells that are recognized by activating receptors on Natural Killer (NK) cells, triggering an immune response.

Innate Lymphoid Cells (ILCs)

This large group of cells, part of the immune system, are similar to lymphocytes but do not possess T cell receptors (TCRs).

Dendritic Cells

These cells are essential in the innate immune system and activate T cells of the adaptive immune system, bridging the two immune responses.

Activated Dendritic Cells

Within these cells, proteins from ingested pathogens are processed into peptide fragments. These fragments then bind to newly formed MHC proteins, which transport them to the cell surface for presentation to T cells.

Co-stimulatory Proteins

These molecules are displayed on the surface of dendritic cells when activated, and they play a critical role in activating T cells by providing secondary signals.

Pathogen-Associated Molecular Patterns (PAMPs)

These are unique components of microbes, such as proteins, lipids, sugars, or nucleic acids, that are recognized by receptors on host cells, signaling the presence of a pathogen.

Pattern Recognition Receptors (PRRs)

These receptors recognize PAMPs, including Toll-like receptors (TLRs), allowing immune cells to detect and respond to pathogens.

Complement System

This is a group of blood proteins that activate in a cascade to combat infections by directly attacking pathogen membranes, promoting inflammation, and marking microbes for phagocytosis.

Phagocytes

These cells engulf and destroy pathogens using hydrolytic enzymes, antimicrobial peptides, and toxic oxygen molecules. They also release signaling molecules to initiate an inflammatory response.

Type I Interferons (IFNα and IFNβ)

These proteins are produced by virus-infected cells to inhibit viral replication in other cells and enhance the killing activity of natural killer (NK) cells.

Natural Killer (NK) Cells

These cells target and kill infected host cells, especially those with high levels of activating surface proteins and reduced amounts of class I MHC proteins.

Immunological Self-Tolerance

This is the crucial capability of immune cells to avoid reacting against the body's own molecules and cells, preventing autoimmune reactions.

Adjuvant

This is a substance, often microbial, that is mixed with an antigen in a vaccine to enhance the immune response by activating pattern recognition receptors (PRRs).

Antibodies

These proteins are produced by B cells and circulate in the blood and other body fluids, binding specifically to foreign antigens to neutralize or eliminate them.

Antibody Responses

These responses involve the activation of B cells to secrete proteins that specifically bind to foreign antigens, aiding in their neutralization or elimination from the body.

T Cell-Mediated Immune Responses

These responses occur when T cells recognize foreign antigens bound to MHC proteins on the surface of host cells, leading to targeted immune actions.

Antigen-Presenting Cells (APCs)

These specialized cells display antigens to T cells, initiating an immune response.

Autoimmune Disease

This occurs when T or B cells mistakenly target and react against the body’s own molecules, leading to tissue damage and dysfunction.

Clonal Expansion and Differentiation into Memory Cells

These mechanisms create immunological memory by causing B and T cells that recognize an antigen to proliferate, and some to develop into long-lived cells for future responses.

Antibodies

These secreted proteins defend against extracellular pathogens by binding to viruses and microbial toxins and recruiting components of the innate immune system.

Immunoglobulins (Igs)

Also known as antibodies, these proteins are produced exclusively by B cells, each with a unique antigen-binding site, and are abundant in the blood.

Activation-Induced Deaminase (AID)

This enzyme initiates switch recombination by deaminating cytosines to uracil in switch sequences to diversify the types of immunoglobulins produced.

Cytotoxic T Cells (TC cells)

These cells directly kill infected host cells by secreting perforins and granzymes, inducing apoptosis.

Helper T Cells (TH cells)

These cells assist B cells in producing antibody responses, enable macrophages to destroy microorganisms, and help dendritic cells activate cytotoxic T cells.

Regulatory T Cells (Treg cells)

These cells suppress the activity of other immune cells by producing suppressive proteins, helping to maintain immune homeostasis and prevent autoimmunity.

T Cell Receptors (TCRs)

These are antigen receptors found on the surface of T cells that enable them to recognize and respond to specific antigens.