Immunology — Innate and Adaptive Immunity (Lecture Notes)

Vocabulary flashcards covering key terms from the notes on the immune system, including innate and adaptive immunity, phagocytosis, inflammation, and mediators.

Immune System

The host defense system against infectious diseases and foreign (nonself) antigens.

Innate Immunity

The first, nonspecific defense; rapid, at the initial infection site; lacks immunologic memory; present at birth.

Adaptive Immunity

The specific second defense system; recognizes and destroys particular pathogens; develops with life; slower but with memory.

Natural Immunity

Immunity acquired naturally, including passive maternal antibodies and infection-induced active immunity.

Passive Natural Immunity

Antibodies transferred from mother to fetus via placenta or to infant via breast milk.

Active Natural Immunity

Body produces antibodies after exposure to an infection.

Artificial Immunity

Immunity obtained through artificial means, including passive antibody transfer and active vaccination.

Passive Artificial Immunity

Immediate protection from ready-made antibodies transferred to a person (e.g., antiserum, antivenom).

Active Artificial Immunity

Immunity developed after vaccination; the body makes antibodies and memory cells.

Antibody

A protein produced in response to a specific antigen; part of the humoral immune response.

Antigen

A substance that induces the production of antibodies.

Defensin

Antimicrobial peptides in innate defense; disrupt bacterial membranes, abundant in GI and lower airways.

Beta-defensin

Defensin secreted by epithelial cells in the respiratory tract.

Toll-like Receptors (TLRs)

Pattern-recognition receptors that detect PAMPs and trigger inflammatory signaling.

NOD-like Receptors (NLRs)

Cytoplasmic sensors of microbial products; activate NF-κB and inflammation.

RIG-I-like Helicases

Cytoplasmic sensors of viral RNA that trigger type I interferons to inhibit replication.

MDA-5

A RIG-I-like receptor; senses viral RNA in the cytoplasm and induces type I interferons.

Pattern Recognition Receptors (PRRs)

Receptors that detect conserved microbial patterns to initiate innate responses.

PAMPs

Pathogen-associated molecular patterns recognized by PRRs.

Phagocytosis

Engulfment and digestion of pathogens by phagocytes.

Phagosome

Vesicle formed when a pathogen is engulfed by a phagocyte.

Phagolysosome

Phagosome fused with lysosome; where digestion occurs.

Opsonization

Coating of pathogens with antibodies or complement to enhance phagocytosis.

Phagocytes

Cells capable of phagocytosis, including neutrophils, monocytes/macrophages, eosinophils, basophils, and dendritic cells.

Neutrophil

Short-lived granulocyte; primary phagocyte that digests pathogens; often undergoes apoptosis after function.

Eosinophil

Granulocyte involved in parasitic defense and allergic responses; releases toxic proteins.

Basophil

Granulocyte that releases histamine during allergic responses.

Monocyte

Circulating precursor that differentiates into macrophages or dendritic cells in tissues.

Macrophage

Phagocyte in tissues; engulfs pathogens, presents antigens, and secretes cytokines.

Kupffer Cells

Liver macrophages.

Microglia

CNS macrophages.

Dendritic Cell

Antigen-presenting cell that activates T cells and secretes cytokines; key in initiating adaptive immunity.

Natural Killer (NK) Cells

Innate lymphocytes that kill virus-infected and tumor cells.

KIRs

Killer-cell immunoglobulin-like receptors on NK cells; recognize MHC class I and inhibit killing of healthy cells.

Lectin-like Receptors

Receptors that bind sugars/proteins; part of innate recognition (activating and inhibitory).

Complement System

A proteolytic cascade of ~30 serum proteins that cause lysis, opsonization, and inflammation.

Classical Pathway

Complement activation triggered by antibodies bound to pathogens.

Alternative Pathway

Antibody-independent complement activation initiated by microbial surfaces.

Lectin Pathway

Complement activation via mannose-binding lectin (MBL); antibody-independent.

Opsonins

Molecules (antibodies, C3b) that coat pathogens and enhance phagocytosis.

Anaphylatoxins

C3a and C5a; promote inflammation and recruit phagocytes.

Histamine

Vasoactive mediator from mast cells and basophils causing vasodilation and increased vessel permeability.

Kinins

Plasma mediators that promote chemotaxis and inflammation.

Prostaglandins

Lipid mediators that amplify inflammation and cause fever; sensitize nerves.

Leukotrienes

Lipid mediators that increase vascular permeability and recruit leukocytes.

Cytokines

Signaling proteins that regulate immune responses; include IL-1, IL-6, and TNF-α.

IL-1

Pro-inflammatory cytokine from macrophages; induces fever and activates other immune cells.

IL-6

Cytokine with pro- and anti-inflammatory roles; stimulates acute-phase response.

TNF-α

Pro-inflammatory cytokine; induces fever and recruits immune cells.

Inflammation

Local tissue response to injury or infection: vasodilation, permeability, chemotaxis, phagocytosis, healing.

Cardinal Signs of Inflammation

Rubor, Tumor, Calor, Dolor, Functio laesa.

Fever

Systemic rise in body temperature during inflammation; regulated by hypothalamus.

Pyrogens

Substances that raise body temperature (e.g., IL-1).

Type I Interferons

IFN-α and IFN-β; antiviral cytokines that inhibit viral replication.

Interferons

Cytokines with antiviral and immunomodulatory effects.

Chemotaxis

Movement of immune cells toward a chemical signal at the infection site.

MHC Class I

Molecules on nucleated cells presenting self-antigens; recognized by NK cell receptors.

Antigen-Presenting Cells (APCs)

Cells that process and present antigens to T cells (e.g., dendritic cells, macrophages).

Pattern Recognition Receptors (PRRs)

Receptors that detect conserved microbial patterns to initiate innate responses.