🛡️ Immunology &amp; Disease

Immune System

The body's defence network of cells, tissues and molecules that protects against pathogens.

Viruses

Non-cellular infectious particles of genetic material in a protein coat that reproduce only inside host cells.

Innate Immunity

Rapid, non-specific defences such as skin, mucus, phagocytes and inflammation.

Adaptive Immunity

Slower, specific defence involving lymphocytes that remember pathogens.

White Blood Cells

Leukocytes including neutrophils, lymphocytes and macrophages that fight infection.

Antibodies

Y-shaped proteins made by B cells that bind specific antigens and mark them for destruction.

Antigens

Molecules, usually on pathogens, that trigger an immune response.

Vaccines

Preparations that train the immune system to recognise a pathogen without causing the disease.

Herd Immunity

Indirect protection of unvaccinated people when enough of a population is immune.

Inflammation

A response with redness, heat, swelling and pain that brings immune cells to damaged tissue.

Fever

A raised body temperature that can slow pathogen growth and boost immune activity.

Allergies

Overreaction of the immune system to harmless substances like pollen or peanuts.

Infectious Disease Transmission

Pathogens spread by air, water, food, contact or vectors such as mosquitoes.

Bacterial vs Viral Infections

Antibiotics treat bacterial infections but do not work against viruses.

Epidemic and Pandemic

An epidemic is a sudden outbreak in a region, while a pandemic spreads worldwide.

Intermediate topics (19)

Virus Structure

A nucleic acid genome enclosed in a capsid, sometimes with an outer lipid envelope and spike proteins.

Viral Replication Cycle

Attachment, entry, replication, assembly and release; phages follow lytic or lysogenic cycles.

Retroviruses

RNA viruses like HIV that use reverse transcriptase to make DNA that integrates into the host genome.

Phagocytosis

Cells such as macrophages engulf and digest pathogens in a vesicle.

Complement System

A cascade of blood proteins that punches holes in microbes and enhances phagocytosis.

Natural Killer Cells

Innate lymphocytes that destroy virus-infected and tumour cells lacking normal MHC markers.

B Lymphocytes

Cells that mature into plasma cells producing antibodies and into memory B cells.

T Lymphocytes

Cells that mature in the thymus; helper T cells coordinate immunity and cytotoxic T cells kill infected cells.

Clonal Selection

An antigen selects the lymphocyte that recognises it, which multiplies into effector and memory clones.

Primary and Secondary Response

The first exposure produces a slow, weak response; re-exposure triggers a faster, stronger one via memory cells.

Antibody Classes

IgG, IgM, IgA, IgE and IgD differ in structure, location and function.

Active and Passive Immunity

Active immunity is made by your own response; passive immunity is received as ready-made antibodies.

MHC Molecules

Surface proteins that display peptide fragments to T cells, distinguishing self from non-self.

Autoimmune Disease

The immune system attacks the body's own tissues, as in type 1 diabetes and rheumatoid arthritis.

Blood Groups and Transfusion

ABO and Rh antigens on red cells determine compatible donors, since mismatches trigger agglutination.

Immunodeficiency

Defective immune function, inherited like SCID or acquired like AIDS, causing frequent infections.

HIV and AIDS

HIV infects helper T cells; untreated infection depletes them, leaving the body vulnerable to opportunistic infections.

Epidemiology

The study of how disease is distributed and what determines it in populations.

Basic Reproduction Number

R0 is the average number of new infections one case causes in a fully susceptible population.

Advanced topics (18)

Antibody Diversity

V(D)J recombination and somatic hypermutation generate billions of distinct receptors and antibodies.

T Cell Receptor Signalling

Recognition of peptide-MHC with co-stimulation activates T cells through kinase cascades like ZAP-70.

Immunological Tolerance

Central and peripheral mechanisms eliminate or suppress self-reactive lymphocytes to prevent autoimmunity.

Cytokines

Small signalling proteins such as interleukins and interferons that coordinate immune cell behaviour.

Toll-Like Receptors

Innate receptors that detect conserved microbial patterns and trigger inflammatory signalling.

Antigenic Variation

Pathogens such as influenza and trypanosomes alter surface antigens to evade immunity.

mRNA Vaccines

Lipid-encapsulated mRNA instructs host cells to make an antigen, inducing immunity without infection.

Monoclonal Antibodies

Identical antibodies from a single B cell clone, used in diagnostics and cancer therapy.

Immune Checkpoint Therapy

Drugs blocking inhibitory receptors such as PD-1 release T cells to attack tumours.

CAR-T Cell Therapy

Patient T cells are engineered with chimeric receptors to recognise and kill cancer cells.

Hypersensitivity Types

Four types, I to IV, describe immediate IgE reactions, cytotoxic, immune complex and delayed T cell responses.

Transplant Rejection

Recipient immune cells recognise donor MHC as foreign, requiring matching and immunosuppression.

Innate Lymphoid Cells

Tissue-resident lymphocytes that rapidly secrete cytokines but lack antigen-specific receptors.

Inflammasomes

Cytosolic complexes that activate caspase-1 to release IL-1 beta and trigger pyroptosis.

Virus Evolution

High mutation rates and reassortment allow viruses like influenza to evolve and jump species.

Zoonotic Spillover

Pathogens jump from animals to humans, as with coronaviruses, Ebola and avian influenza.

Mathematical Epidemiology

SIR and related compartment models predict epidemic dynamics and the effect of interventions.

Immunosenescence

Age-related decline in immune function, raising susceptibility to infection and cancer.