MEDL 234: Weeks 1-7 Lecture Flashcards

Comprehensive vocabulary and concept flashcards covering introductory immunology, innate and adaptive responses, lymphocyte development, effector mechanisms, tolerance, oncology, transplantation, and immunodeficiency based on lecture transcripts.

Innate Immunity

The early defense against infections that provides rapid responses through anatomical barriers, phagocytes, and soluble proteins.

Adaptive Immunity

An immune response that develops slowly but is highly specific and mediated by B and T lymphocytes.

Sentinel Cells

Resident cells in tissues, such as macrophages, dendritic cells (DCs), and mast cells, that detect microbes.

Natural Killer (NK) Cells

Innate lymphoid cells that kill infected or stressed cells, often identifying cells with downregulated MHC Class I.

C3a and C5a

Complement fragments that act as anaphylatoxins to stimulate inflammation by recruiting and activating leukocytes.

C3b

A complement protein fragment that coats microbes to promote opsonization and phagocytosis.

Membrane Attack Complex (MAC)

A complex formed by complement proteins ${C5b, C6, C7, C8, \text{ and } C9}$ that creates pores in microbial membranes leading to lysis.

TNFα and IL-1

Cytokines secreted by macrophages and dendritic cells that activate endothelial cells and induce fever in the hypothalamus.

MHC Class I

Molecules expressed on all nucleated cells that present cytosolic (endogenous) peptides to CD8+ cytotoxic T lymphocytes.

MHC Class II

Molecules expressed on professional antigen-presenting cells (APCs) that present internalized (exogenous) peptides to CD4+ helper T lymphocytes.

Pax-5

The transcription factor required for the commitment of common lymphoid progenitors to the B cell lineage.

Notch-1

The transcription factor required for the commitment of common lymphoid progenitors to the T cell lineage in the thymus.

RAG-1 and RAG-2

Lymphoid-specific recombinases essential for the somatic recombination of BCR and TCR gene segments.

Signal 1

The primary signal for T cell activation generated by the interaction between the peptide-MHC complex and the T cell receptor (TCR).

Signal 2 (Co-stimulation)

The secondary signal for T cell activation, typically through the binding of $CD80/CD86$ (B7) on APCs to $CD28$ on T cells.

CTLA-4 and PD-1

Inhibitory receptors on T cells that provide negative regulation to terminate immune responses or maintain self-tolerance.

Th1 Subset

A CD4+ T cell subset that secretes $IFNγ$ to activate macrophages and is driven by the transcription factor T-bet.

Th2 Subset

A CD4+ T cell subset that secretes $IL-4, IL-5, \text{ and } IL-13$ to defend against helminths and is driven by GATA-3.

Th17 Subset

A CD4+ T cell subset that secretes $IL-17 \text{ and } IL-22$ to recruit neutrophils and is driven by RORγt.

Regulatory T Cells (Tregs)

Effector T cells that inhibit immune responses, express $CD25$, and are dependent on the transcription factor FoxP3.

Activation-Induced Deaminase (AID)

An enzyme induced in B cells by Tfh signals that is essential for heavy-chain isotype switching and affinity maturation.

IgG

An antibody isotype with a mean serum half-life of $23 \text{ days}$ that mediates opsonization, complement activation, and neonatal immunity.

IgE

An antibody isotype that mediates defense against helminthic parasites and triggers immediate hypersensitivity (allergy).

Antigenic Drift

The process where point mutations in viral genes lead to new strains, causing yearly epidemics.

Antigenic Shift

A major genetic change resulting from the recombination of human and nonhuman viral genomes, potentially leading to pandemics.

Central Tolerance

A process in generative lymphoid organs where developing lymphocytes that recognize self-antigens are deleted or edited.

AIRE Gene

Encodes a protein that allows thymic epithelial cells to express peripheral tissue self-antigens for T cell central tolerance.

Molecular Mimicry

A mechanism of autoimmunity where microbial antigens cross-react with self-antigens, such as in rheumatic fever.

CAR-T Cells

Genetically engineered T cells expressing a Chimeric Antigen Receptor that recognizes tumor surface antigens independently of MHC.

Hyperacute Rejection

Rejection occurring within minutes to hours due to pre-existing anti-donor antibodies in the recipient.

Graft Versus Host Disease (GVHD)

A complication of HSCT where mature alloreactive donor T cells in the graft attack the recipient's tissues.

Type I Hypersensitivity

Immediate hypersensitivity caused by IgE-mediated mast cell degranulation in response to environmental allergens.

Type IV Hypersensitivity

Delayed-type hypersensitivity mediated by T lymphocytes rather than antibodies, as seen in the tuberculin reaction or Celiac disease.

SCID (Severe Combined Immunodeficiency)

A group of congenital disorders characterized by defects in both B and T cell arms of the immune system, such as $ADA$ or $RAG$ mutations.

HIV Life Cycle

The retroviral process involving binding via $gp120$, reverse transcription of RNA to DNA, and integration into the host genome.

ART (Antiretroviral Therapy)

A triple-drug therapy that blocks HIV reverse transcriptase, protease, and integrase to lower viral load.