KGI: Introduction to Viruses and the Immune Response Lecture 1

Vocabulary flashcards covering key terms from the lecture notes on viruses and the immune response.

Virus

A microscopic infectious agent that replicates only inside a host cell; consists of nucleic acid (DNA or RNA) inside a protein capsid, and sometimes a lipid envelope; non-living outside a host.

Envelope

Lipid membrane surrounding some virions derived from the host cell, containing viral glycoproteins for entry.

Capsid

Protein shell that encases the viral genome, built from capsomeres and protecting the nucleic acid.

Glycoprotein (Spike)

Viral surface protein embedded in the envelope that mediates attachment and entry into host cells.

Nucleic acid genome

The viral genetic material, which can be DNA or RNA and be single- or double-stranded.

Baltimore classification system

A seven-class system classifying viruses by genome type and replication strategy to produce mRNA and viral proteins.

V(D)J recombination

Rearrangement of variable (V), diversity (D), and joining (J) gene segments to create diverse antigen receptor genes in B and T cells.

Naked virus

A virus lacking a lipid envelope; consists only of the nucleocapsid.

Enveloped virus

A virus with a lipid envelope containing embedded proteins; typically more sensitive to environmental conditions.

Virion

Complete infectious virus particle outside a host cell.

Nucleic acid genome (concept)

Viral genome made of DNA or RNA, single- or double-stranded, determining replication strategy.

DNA-dependent RNA polymerase

Enzyme that transcribes RNA from a DNA template (used by certain DNA viruses or viruses that carry their own polymerase).

RNA-dependent RNA polymerase

Viral enzyme that copies RNA from an RNA template, essential for replication of many RNA viruses.

Reverse transcriptase

Enzyme that copies RNA into DNA; used by retroviruses to integrate into the host genome.

mRNA

Messenger RNA; transcripts used by ribosomes to synthesize viral or cellular proteins.

MHC I

Major histocompatibility complex class I; presents endogenous peptides on nearly all nucleated cells to CD8+ T cells.

MHC II

Major histocompatibility complex class II; presents exogenous peptides on professional antigen-presenting cells to CD4+ T cells.

Antigen-presenting cell (APC)

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

Dendritic cell

Professional APC that initiates adaptive immunity by presenting antigen to naïve T cells.

Natural Killer (NK) cells

Innate immune cells that detect abnormal MHC I expression and kill infected or stressed cells via cytotoxic mechanisms.

B cell

Lymphocyte that recognizes antigen and can differentiate into plasma cells to produce antibodies; can form memory B cells.

T cell

Lymphocyte that mediates adaptive immunity; includes CD4+ helper T cells and CD8+ cytotoxic T cells.

Antibody (immunoglobulin)

Protein produced by plasma cells that binds antigens via the Fab region and engages immune effector functions via the Fc region.

Fab region

Antigen-binding fragment of an antibody that recognizes and binds to epitopes.

Fc region

Fragment crystallizable region of an antibody that binds Fc receptors and mediates effector functions.

Epitope

Specific part of an antigen recognized by an antibody or T-cell receptor.

Plasma cell

Differentiated B cell that secretes large amounts of antibodies.

Memory B cell

Long-lived B cell that remains after an infection to respond quickly upon re-exposure.

Memory T cell

Long-lived T cell that responds rapidly to re-exposure to the antigen.

TH1

Helper T cell subset that promotes cell-mediated immunity by activating macrophages and cytotoxic T cells.

TH2

Helper T cell subset that promotes humoral immunity by aiding B cells and activating eosinophils and mast cells.

TH17

Helper T cell subset that recruits neutrophils and drives inflammatory responses.

Treg (regulatory T cells)

T cells that suppress immune responses to maintain tolerance and prevent autoimmunity.

Humoral immunity

Adaptive immunity mediated by antibodies produced by B cells in the extracellular space.

Cell-mediated immunity

Adaptive immunity mediated by T cells that attack infected cells and coordinate responses.

Passive immunity

Immunity conferred by transfer of antibodies from another person or source (natural or artificial).

Active immunity

Immunity acquired through infection or vaccination, resulting in memory formation.

Vaccination

Artificial active immunity achieved by exposure to antigen to stimulate immune memory.

Monoclonal antibodies

Antibodies produced from a single clone for consistent, specific binding; used in passive immunotherapy.

Fc receptor

Receptor on immune cells that binds the Fc region of antibodies, enabling processes like phagocytosis and antibody-dependent cytotoxicity.

Perforins

Cytotoxic proteins released by NK cells and cytotoxic T cells that form pores in target cell membranes to induce death.

Proteosome

Cytosolic protein complex that degrades proteins into peptides for presentation by MHC I.

Viral evasion

Strategies used by viruses to escape immune responses, including mutation, latency, molecular mimicry, and interference with cytokines or signaling pathways.

Where are mRNA translated into proteins

into proteins, primarily in the ribosomes of the cytoplasm.

Where is mRNA transcribed

in the nucleus of the cell.

Can viruses replicate on there own

No, viruses require a host cell for replication.

Are phage viruses specific?

Yes, bacteriophages are specific to particular bacterial hosts. Ex. plant viruses only effect plants

With what can you see a virus with

an electron microscope.

What does a virus bring thats essential for it replication

A virus brings its own genetic material, either DNA or RNA, which is essential for its replication inside a host cell.

When does a virus need to bring it’s own replicase (RNA-dependent RNA polymerase, RdRp)

A virus brings its own genetic material, either DNA or RNA, which is essential for its replication inside a host cell. and in Negative-sense RNA viruses → must bring RdRp with them

Why cant negative stranded DNA be directly translated?

Because it must first be converted into a positive-strand mRNA by a viral enzyme before protein synthesis can occur.

Why are DNA viruses more stable?

DNA viruses are more stable because their double-stranded structure provides greater resistance to degradation and mutations compared to RNA viruses.

What are the 4 types of T- helper cells ?

The four types of T-helper cells are Th1= cell mediated Immunity, Th2=humoral immunity, Th17=Cell mediated inflammation autoimmune disease, and Treg =Immunoregulation

Th1 treats what type of foreign intruder

Th1 cells primarily target intracellular pathogens, such as viruses and certain bacteria, by activating macrophages and promoting cell-mediated immunity.

Th2 treats what type of foreign intruder

Th2 cells primarily target extracellular pathogens, such as parasites and allergens, by promoting antibody production and activating eosinophils.

Th17 treats what type of foreign intruder

Th17 cells primarily target extracellular bacteria and fungi, contributing to inflammatory responses and autoimmune diseases.

TREG treats what type of foreign intruder

TREG cells primarily regulate immune responses and inhibit excessive inflammation rather than directly targeting specific foreign intruders, maintaining immune homeostasis.

B cell MHC II presented anitgen stimulates what T helper cell

Th2 cells, leading to antibody production and immune response against extracellular pathogens.

What do B cell recognize

B cells recognize whole protein antigens

What do T cell recognize

short viral peptides

What is Tc

cytotoxic T cell that kills infected cells and tumor cells.

What is Th

a type of T cell responsible for helping B cells produce antibodies and enhancing the immune response.

What does a NK T cell bind to on pathogen?

the Fc region of an antibody

Mast Cells?

histamine and other mediators during allergic responses and inflammation, . release chemicals that signal injury

Basophils?

a type of white blood cell that releases histamine, heparin, and serotonin and contributes to inflammatory responses, particularly in allergies.

Eosinophils?

can phagocytize pathogens and produce anti-histamines

What region of an anitbody is the binding region

Fab Region

What region of an anitbody activates immune cells

Fc Region

What do Dendritic Cells do

Dc internalize the pathogen digest it and display present foreign peptide on surface through the MHC II to activate T cells.

What are PRRs

Pattern Recognition Receptors that identify pathogens and activate immune responses.

What do PRRs recognize?

They recognize specific molecular patterns associated with pathogens. PAMPs

What is the first line of defense known as

Mechanical Immunity

Is innate immunity specific?

No, innate immunity is non-specific and responds to a broad range of pathogens.

What are naked viruses

Naked viruses are viruses that lack a lipid envelope, consisting only of a protein coat and genetic material. They are more resistant to environmental conditions than enveloped viruses.

What doe viruses steal from the host?

membrane

What do all viruses have in common

the presence of genetic material, either DNA or RNA, surrounded by a protein coat called a capsid.