7A–7E Dealing with Disease — Immunology Flashcards (Video Notes)

A set of Q&A flashcards covering self vs non-self, antigens, MHC, pathogen types, innate and adaptive immunity, inflammation, lymphatics, antibodies, memory, vaccines, and related clinical topics from the notes.

What is the difference between self and non-self antigens in the immune system?

Self antigens are markers on our own cells (e.g., MHC) that identify them as 'self'; non-self antigens are foreign molecules that trigger an immune response.

What are MHC Class I and Class II markers and where are they located?

MHC Class I markers are on all nucleated body cells and mark them as self; MHC Class II markers are on specialized antigen-presenting cells and interact with helper T cells during antigen presentation.

What is an autoimmune disease?

A condition in which the immune system attacks the body's own cells because self–non-self distinction fails (e.g., rheumatoid arthritis, lupus).

What is an allergen?

A non-pathogenic antigen that triggers an allergic reaction in some people (e.g., pollen, dust, peanuts).

What are the ABO blood group antigens and which type is universal donor/recipient?

RBC antigens A and B; Type A has A, Type B has B, Type AB has both, Type O has neither. Type O is universal donor; Type AB is universal recipient.

What are the two main categories of pathogens by cellularity?

Cellular pathogens (bacteria, fungi, protozoa, worms) and non-cellular pathogens (viruses, prions).

What are extracellular and intracellular pathogens?

Extracellular pathogens act outside cells; intracellular pathogens invade/replicate inside host cells (e.g., viruses).

What is a vector in disease transmission?

An organism (e.g., ticks, mosquitoes) that transmits pathogens between hosts.

Name three major cellular components of the second line of defence (white blood cells).

Neutrophils, macrophages, dendritic cells.

What is antigen presentation?

The process by which antigen-presenting cells display processed antigens on MHC molecules to T cells.

What is the role of natural killer (NK) cells?

NK cells recognize cells with reduced MHC I or stress markers and kill them to help prevent viral spread and cancer.

What is fever and what role does it play in immunity?

A rise in body temperature that helps inhibit pathogen enzymes and supports immune responses; prolonged fever can be harmful.

What are lysozymes and where are they found?

Enzymes that destroy bacterial cell walls; found in tears, saliva, mucus, and other secretions.

What is an antigen-presenting cell and give examples?

A cell (e.g., macrophages, dendritic cells, B cells) that presents antigens via MHC II to T helper cells to initiate adaptive immunity.

What is clonal selection?

The process by which B or T cells with receptors matching an antigen are selected for proliferation.

What is clonal expansion?

Rapid proliferation of the selected B or T cell clone after activation.

What is immunological memory?

The ability of the immune system to respond more rapidly and effectively to a pathogen upon re-exposure due to memory B and T cells.

How do vaccines relate to immunological memory?

Vaccines stimulate the adaptive immune system to generate memory cells without causing disease.

What is the basic structure of an antibody?

A Y-shaped protein with two heavy chains and two light chains, a constant region and a variable region, and two antigen-binding sites.

What are the five classes of antibodies and a key function of each?

IgA (mucosal secretions), IgD (B cell activation), IgE (allergic responses/parasites), IgG (most abundant; crosses placenta), IgM (first antibody produced).

What are four main functions of antibodies in the humoral response?

Neutralisation, agglutination, immobilisation, opsonisation, and activation of the complement system.

Where do antigen-presenting cells activate the adaptive immune system and why?

In secondary lymphoid tissues (e.g., lymph nodes, spleen) where APCs present antigens to T and B cells to initiate clonal selection.

What is the difference between humoral and cell-mediated immunity?

Humoral immunity involves antibodies produced by B cells to target extracellular pathogens; cell-mediated immunity involves cytotoxic T cells destroying infected or abnormal cells.

What triggers organ transplant rejection and how is it mitigated?

Mismatched donor MHC antigens trigger rejection; immunosuppressants reduce rejection but increase infection risk.

What is a prion and how is it different from other pathogens?

Prions are abnormally folded proteins that cause disease without containing nucleic acids and do not reproduce like living organisms.

Describe the basic structure of a virus and whether viruses can be cultured on standard nutrient agar.

Viruses have genetic material (DNA or RNA) inside a protein coat; many have a lipid envelope. They cannot replicate independently and are not cultured on standard nutrient agar.

Which pathogen type would be affected by antibiotics that target cell wall synthesis?

Bacteria (cell wall-targeting antibiotics do not affect viruses or prions).

What is the role of the lymphatic system in immunity?

A network that transports antigen-presenting cells and pathogens to lymph nodes and sites of clonal selection; also drains tissue fluid and aids leukocyte production.

What is the difference between primary and secondary lymphoid tissues?

Primary lymphoid tissues (bone marrow, thymus) produce and mature lymphocytes; secondary lymphoid tissues (lymph nodes, spleen, tonsils) are sites of maturation, activation, and clonal selection.

What happens during the inflammatory response?

Cytokines and histamine cause initiation; vasodilation increases blood flow; phagocytes and complement migrate to the site to destroy pathogens and debris; results in swelling and redness.

What is the role of macrophages and dendritic cells in immunity?

They are antigen-presenting cells that engulf pathogens and present their antigens to T helper cells to activate adaptive immunity.

What is an allergen and how does an allergic reaction occur at the cellular level?

An allergen triggers IgE production, mast cell sensitisation; upon re-exposure, IgE triggers degranulation of mast cells releasing histamine, causing allergy symptoms.

What is the role of memory B and memory T cells after an infection or vaccination?

They persist long-term and enable a faster, stronger response upon re-exposure to the same antigen.

Explain the concept of MHC compatibility in organ transplantation and why donor–recipient matching matters.

Matching donor and recipient MHC (HLA) reduces immune recognition of the transplant as non-self, lowering rejection risk; immunosuppressants are used if mismatches occur.

What is a non-self antigen in the context of organ transplantation?

MHC molecules from the donor organ that differ from those of the recipient and trigger an immune response.

What is the role of the spleen in the immune system?

A secondary lymphoid organ that acts as a site for immune cell interactions, clonal selection, and memory formation; also filters blood.

What is the role of interferons in antiviral defense?

Interferons are cytokines released by infected cells that increase resistance of neighboring cells to viral infection.

What is the complement system and what are its major outcomes?

A cascade of proteins that opsonise pathogens, attract phagocytes (chemotaxis), and form the membrane attack complex to lyse pathogens.