MLS Review: Chapters 1-6 Intro to Immune System

Practice flashcards covering nomenclature, cells, tissues, and effector mechanisms of the innate and adaptive immune systems based on MEDL 234 lecture review.

Innate (Natural) Immunity

Defense mechanisms existing from birth including anatomic, physiologic, phagocytic, and inflammatory barriers that recognize shared microbial structures called PAMPS and provide an immediate first-line defense without memory.

Adaptive (Acquired) Immunity

Immune responses mediated by lymphocytes expressing highly diverse receptors that generate immunological memory for faster recognition of previously encountered pathogens.

PAMPS

Pathogen-associated molecular patterns; structures shared by microbes that are recognized by the innate immune system.

DAMPs

Damage-associated molecular patterns; products of dead tissue recognized by the innate immune system.

Neutrophils

Short-lived phagocytes recruited from blood and bone marrow to infection sites that ingest and destroy microbes; dead neutrophils and bacteria form pus.

Macrophages

Phagocytes found in tissues that develop from monocytes, act as antigen-presenting cells (APCs), and release cytokines to induce inflammation or aid in tissue repair.

Dendritic Cells (DCs)

Sentinel cells in tissue that provide a link between innate and adaptive immunity by capturing antigens and moving to draining lymph nodes to interact with naive T cells.

Natural Killer (NK) Cells

Cells of the innate immune system that recognize and kill abnormal cells (stressed, virus-infected, or tumor) and produce cytokines like IFN\text{\fontsize{10}{12}\textgamma}.

Humoral Immunity

A component of adaptive immunity where antigen-specific B cells are stimulated to become plasma cells secreting antibodies that neutralize microbes and toxins.

Cell-Mediated Immunity (CMI)

A component of adaptive immunity where Tfh cells help B cells, Th cells help macrophages, and Tc cells kill altered or infected cells.

Antigen Presenting Cells (APCs)

Cells such as dendritic cells, macrophages, and B cells that capture and display peptides from antigens for recognition by T lymphocytes.

MHC Class I

Molecules expressed on all nucleated cells that present peptides derived from cytosolic proteins to $CD8^+$ T cells.

MHC Class II

Molecules expressed mainly on DCs, macrophages, and B cells that present peptides from extracellular proteins internalized into vesicles to $CD4^+$ T cells.

Human Leukocyte Antigens (HLA)

The term used for human MHC molecules; an individual can express up to 6 different class I molecules and 6-14 different class II molecules.

Affinity

The term used to describe the strength with which one antigen-binding site of an antibody binds to one epitope of an antigen.

Avidity

A measure of the overall strength of binding of an antigen with many antigenic determinants and multivalent antibodies.

V(D)J Recombinase

An enzyme complex composed of RAG-1 and RAG-2 proteins that binds to recombination signal sequences (RSS) to mediate somatic recombination in immature B and T cells.

Adjuvant

A substance mixed with an antigen to enhance the immune response by providing a 'danger' signal and increasing costimulator expression on APCs.

Th1 Subset

A subset of $CD4^+$ T cells that secretes IFN\text{\fontsize{10}{12}\textgamma}, uses the transcription factor T-bet, and activates macrophages to kill phagocytosed microbes.

Th2 Subset

A subset of $CD4^+$ T cells that secretes $IL-4$, $IL-5$, and $IL-13$, uses the transcription factor GATA3, and helps control helminthic parasite infections.

Th17 Subset

A subset of $CD4^+$ T cells that secretes $IL-17$ and $IL-22$, uses the transcription factor ROR\text{\fontsize{10}{12}\textgamma}t, and enhances neutrophil recruitment for defense against extracellular bacteria and fungi.

Regulatory T cells (Tregs)

T cells involved in immune tolerance and regulation that require the transcription factor FOXP3.

Perforin

A protein released by CTLs that allows the delivery of granzymes into the cytosol of a target cell.

Granzymes

Granule enzymes delivered by CTLs that cleave and activate caspases in the target cell to induce apoptosis.

Fas Ligand (FasL)

A membrane protein expressed by activated CTLs that binds to Fas (CD95) on target cells to induce apoptosis without requiring cytotoxic granules.