Medical immunology

Mast Cells

Type of granulocyte that’s crucial in allergic reactions that release mediators like histamine, leukotrienes, and prostaglandins.

Activation potentially causing local inflammation and allergic symptoms.

Neutrophils

Short-lived phagocytes that are the initial responders in innate immunity, engaging in engulfing pathogens, producing reactive oxygen species, and releasing enzymes that attract more immune cells.

Basophils

Type of granulocyte that participates in allergic reactions, by releasing histamine to facilitate vasodilation and recruit immune cells. Primarily found in the bloodstream.

Eosinophils

Granulocytes responsible for fighting parasitic infections and mediating allergic responses. Work by releasing cytotoxic proteins effective against helminths.

Lymphocytes

Specific family of adaptive immune cells. Including B cells, T cells, and NK cells - that recognize and remember pathogens, while targeting infected cells and producing antibodies.

Plasma Cells

Type of activated B cells that produce large amounts of specific antibodies in response to antigens. Crucial for humoral immunity and memory cell generation.

Monocytes

Immune precursor cells that evolve into macrophages and dendritic cells. Involved in clearing dead cells, antigen presentation and cytokine production.

Macrophages

Type of phagocytic cells that engulf pathogens & dead cells, present antigens to T cells. Secrete cytokines and growth factors to enhance inflammation.

MHCs

Cell surface proteins that display processed antigens to T cells. Are essential for the adaptive immune response and self versus non-self distinction.

IgG

Dominant type of antibody in blood that neutralizes toxins, opsonizes pathogens for phagocytosis, and activates complement. Providing long-term immunity.

IgA

Type of antibody located in mucosal areas like the gut and respiratory tract, vital for mucosal immunity and preventing pathogen adherence.

IgM

Type of antibody that’s first generated during infection. Is essential for initial immune response and effective complement activation, due to its pentameric nature.

IgE

Type of antibody associated with allergic reactions and defense against parasites. Plus binding to allergens, causing mast cell degranulation and allergic effects.

IgD

Type of antibody found on B cell surfaces. proposed to be involved in B cell activation and differentiation, though its exact role remains somewhat unclear.

Cytokines

Type of protein that’s generally responsible for signaling and regulating immune responses/inflammation and facilitating communication among immune cells.

Interleukins (ILs)

Subgroup of cytokines that regulates interactions between immune cells, affecting T cell activation and B cell maturation, influencing adaptive immunity.

NK Cells

Type of lymphocyte that can kill virus-infected and tumor cells without prior sensitization and are integral in the innate immune response.

Primary Lymphoid Organs

Sites for initial immune cell development and maturation, including T and B cell generation before antigen activation. Locations include bone marrow and thymus.

Secondary Lymphoid Organs

Site where immune responses are initiated and amplified upon antigen encounter. Locations include lymph nodes, spleen and MALT.

T Lymphocytes/cells

Type of adaptive immune cells that activate other immune cells or eliminate infected cells directly. Including CD4+ (helper) and CD8+ (cytotoxic) T cells.

B cells

Type of cells that produce antibodies and present antigens to T cells. Essential for humoral immunity and developing memory for quicker responses to antigens.

Inflammation

Biological response to harmful stimuli marked by redness, heat, swelling, pain, and loss of function, aimed at protecting the body through injury repair. recruiting immune cells, and activates adaptive im

Complement

Network of over 30 plasma proteins enhancing the actions of antibodies and phagocytes to clear pathogens, vital for both innate and adaptive immunity.

Classical complement

Immune response mechanism triggered when antibodies bind to pathogens. Activating complement proteins and forming the membrane attack complex to lyse pathogen membranes.

Alternative complement

Type of immune response activated when complement proteins bind to pathogen surfaces. Causing enhanced opsonization and inflammation independently of antibodies, crucial in early responses.

Lectin complement

Type of immune response activated when mannose-binding lectin binds to carbohydrates on pathogen surfaces. Stimulating complement proteins for opsonization and clearance.

Complement Regulation

Control mechanisms of a type of immune response. Involve the regulation of: C3 convertase, Cofactors, MAC formation & C1 inhibitor.

Dendritic Cells (DCs)

Antigen-presenting cells essential for T cell activation and initiation of adaptive immune responses, capturing antigens from pathogens.

Macropinocytosis

Process in dendritic cells that involves ingesting significant amounts of extracellular fluids and soluble antigens to enhance antigen capture.

Phagocytosis

Method used by dendritic cells to ingest and degrade cellular debris and pathogens, aiding antigen processing.

Damage assosciated molecular patterns (DAMPS)

Molecules released by stressed, damaged or dying cells. Detected by pattern recognition receptors on dendritic cells, stimulating activation for T cell response.

DC Migration

Moving of mature dendritic cells from peripheral tissues to lymph nodes to present processed antigens to T cells.

DC Maturation

Process that enables dendritic cells to become accurately activated for antigen presentation, marked by increased co-stimulatory molecules and cytokines.

Stimulated by danger signals detected by TLRs.

Interferons (IFNs)

Type of cytokine that stimulates immune responses via ISGs, typically against viruses.

Toll-like Receptors (TLRs)

Type of PRR on immune cells that identifies PAMPs. Triggering innate immune responses and cytokine production.

Viral Nucleic Acid

Viral PAMP detected by TLRs. Activates interferon production and antiviral responses.

Small Virus Evasion

Certain viruses can evade immune detection using:

High mutation rates, stealth tactics to alter antigens and inhibit immune signaling.

Large Virus Evasion

Certain viruses can avoid immune response using:

Disruption of apoptosis, blocking interferon signaling, and downregulating MHC for T cell evasion.

Viral Targeting

Strategy viruses use to interact with specific host signaling pathways. Manipulating cell functions like proliferation and immune responses, to facilitate viral replication.

IFN Stimulated Genes (ISGs)

Genes activated by IFNs that enhance the antiviral state in cells. Including those involved in inhibiting viral replication and modulating immune responses.

Spike Proteins

Structure used by viruses, especially coronaviruses, to bind to host cell receptors, facilitating entry through fusion or endocytosis. Also a PAMP.

Protein Kinases

Enzymes that phosphorylate proteins and play crucial roles in signal transduction pathways and cellular responses.

Viperin

Antiviral protein induced by interferons that disrupts viral replication by inhibiting viral RNA synthesis and modifying the lipid membranes of viruses.

Viral Exit

Process by which newly formed viruses leave the host cell, typically involving budding from the cell membrane or lysis. Allowing them to infect new cells.

Tetherin

Host antiviral protein that tethers newly formed virions to the cell membrane. Preventing their ability to spread and infect other cells.

Soluble Mediators

Biologically active molecules released by immune cells that modulate immune responses. Includes: cytokines, chemokines, and complement proteins.

Innate Defenses/Immunity

First line of defense against pathogens, consisting of physical barriers, phagocytic cells, and the complement system, responding quickly to infections.

Th2 Cells

Subset of CD4+ T helper cells primarily promoting antibody responses and particularly important in mediating allergic reactions and responses to parasitic infections.

Th17 Cells

Subset of CD4+ T helper cells that is involved in autoimmunity and defense against fungal infections and extracellular bacteria.

Group A Strep

Bacterium responsible for various human diseases, including strep throat and skin infections, often leading to complications like rheumatic fever.

Toxic Shock

Severe condition caused by toxins released from bacteria, leading to multi-organ failure and sudden drop in blood pressure, commonly associated with Staphylococcus aureus.

Endotoxic Shock

Potentially fatal condition resulting from the presence of lipopolysaccharides (LPS) in the bloodstream, usually due to Gram-negative bacterial infections.

VacA

Virulence factor produced by H. pylori that disrupts gastric epithelial cell functions, contributing to ulcer formation and evasion of host immune responses.

Type IV Secretion

Bacterial secretion system used for transferring proteins and DNA to target cells, facilitating interaction with host cells and contributing to pathogenesis.

Dengue Fever

Viral infection characterized by high fever, severe headache, pain behind the eyes, joint and muscle pain.

Zika Virus

Arbovirus transmitted primarily by Aedes mosquitoes. Associated with mild rash, fever, and joint pain, notably linked to serious birth defects when pregnant women are infected.

Antigenic (Ag) Variation

Mechanism used by pathogens to change their surface proteins to escape detection by the host immune system, making it difficult for the immune response to recognize and eliminate them.

Host Deletion

Evasion mechanism where a pathogen reduces or disables the host's immune response. To establish infection and promote survival, often by targeting immune cells.

Molecular Mimicry

Evasion mechanism where pathogens display similar structures to host molecules, allowing them to evade the immune response by resembling self-antigens.

Resistance to Killing

Ability of pathogens to survive the killing efforts of the immune system, often through the development of mechanisms that neutralize or evade immune attacks.

Immune Skewing

Evasion mechanism used by pathogens to alter the host immune response to favor their survival. Often by manipulating cytokine profiles or polarizing T cell responses.

Immune Hiding

Evasion mechanism used by pathogens to conceal themselves from the immune system. Often by residing within host cells or in protected niches where detection is limited.

Biofilms

Complex communities of microorganisms attached to surfaces, encased in a self-produced matrix, which confer increased resistance to antibiotics and immune clearance.

Mycobacterium tuberculosis (mTB)

Specific pathogen’s evasion strategy involving: inhibiting phagosome maturation and modulating host immune responses to survive within macrophages.

Listeria monocytes

Pathogen’s evasion strategy involvinh: Intracellular development. LLO secretion to escape from phagosomes and promote cell-to-cell spread.

Phagosome Maturation

Process where phagosomes undergo fusion with lysosomes, resulting in degradation of engulfed materials, with many pathogens evolving mechanisms to inhibit this process.

Yersinia pestis

Bacterium responsible for the plague, employing several virulence factors, including Type III secretion system, to evade the immune response and establish infection.

TLR4 Dampening

Evasion mechanism used by pathogens involving downregulation of a key innate immune receptor. Leading to reduced inflammation and impaired immune responses, allowing potentiallypersistent infections.

Type III Secretion System

Type of apparatus used by many Gram-negative bacteria, including Yersinia, to inject virulence factors directly into host cells. So they can manipulate cell functions.

Pattern Recognition Receptors (PRRs)

General family of receptors that recognise PAMPs or DAMPs.

IL-1B

Pro-inflammatory interleukin produced primarily by activated macrophages. Crucial for the inflammatory response, fever, and activation of other immune cells.

Inflammasome

Multiprotein complex that activates caspase-1. Leading to the maturation of pro-inflammatory cytokines like IL-1β and IL-18. Triggering pyroptosis, an inflammatory form of cell death.

Alarmins

Class of DAMPs where endogenous molecules are released from damaged or dying cells. Alerting the immune system, promoting inflammation and immune activation.

Bacterial Inflammasome Exploit

Exploitation by certain bacteria of the signaling pathways that leads to unnessacary inflammation. Producing factors that mimic host danger signals.

Deficiency in IL-1B

Specific IL deficiency - leading to impaired inflammatory responses and increased susceptibility to infections.

Deficiency in IL-1Ra (DIRA)

Specific interleukin receptor deficiency: Symptoms: extensive pustulosis, diffuse erythema, osteolytic lesions, periosteal elevation.

Treated with recombinant receptor to reduce IL-1B realted inflammation

Deficiency in IL-36

Interleukin deficiency that may result in dysregulated immune responses. Potentially leading to skin disorders and impaired protective immunity.

Type I Allergic Reaction

Autoimmunity mediated by IgE antibodies. This reaction occurs quickly upon exposure to an allergen.

Examples include allergic rhinitis (hay fever) and anaphylaxis. Treatment often involves antihistamines, corticosteroids, and epinephrine.

Type II Allergic Reaction

Autoimmunity mediated by IgG or IgM antibodies that bind to antigens on cell surfaces. Often leading to cell destruction.

Examples include hemolytic anemia and certain drug reactions. Treatment may involve immunosuppressants or plasmapheresis to remove antibodies.

Type III Allergic Reaction

Autoimmunity mediated by immune complexes formed from IgG antibodies and antigens, resulting in inflammation.

Examples include serum sickness and systemic lupus erythematosus (SLE). Treatment typically involves corticosteroids and other anti-inflammatory medications.

Type IV Allergic Reaction

Autoimmunity mediated by T cells (particularly CD4+ and CD8+ T lymphocytes). This reaction is delayed and involves cell-mediated immunity.

Examples include contact dermatitis and tuberculin skin test reactions. Treatment can include corticosteroids and avoidance of the allergen.

Pemphigus vulgaris

An autoimmune disorder characterized by painful blisters and erosions on the skin and mucous membranes, resulting from antibodies targeting desmosomal proteins.

IPEX (Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-linked Syndrome)

A rare autoimmune disorder caused by mutations in the FOXP3 gene, leading to severe immune dysregulation and development of multiple autoimmune conditions.

Pemphigus foliaceus

An autoimmune disease characterized by superficial blisters and crusted lesions. With autoantibodies directed against desmoglein-1.

Systemic Lupus Erythematosus (SLE)

A chronic autoimmune disease that can affect multiple organ systems, characterized by a wide range of symptoms and the production of autoantibodies against nuclear antigens. Example of Type III allergic reaction.

Autoimmunity treatment

Approach usually involving immunosuppressants, corticosteroids, and biologic therapies to control harmful immune responses.

Th1 cells

T helper cells present in acute intracellular infections. Activated by NK’s IL-12, in turn producing their own IL-12, which activates macrophages.

RIG-I Receptors

Pattern recognition receptors that detect viral RNA, activating innate immune responses.

IFN-a

Type I IFN, produced by DCs to trigger antiviral state via ISGs.

IFN-b

Type I IFN, made by Fibrioblasts, to trigger antiviral state via ISGs.

IFN-y

Type II IFN, produced mainly by T cells and NK cells. Functions to promote macrophage activation and enhance antigen presentation by increasing MHCI/II expression.

IL-1a

Type of interleukin activated by: mainly macrophages, neutrophils, epithelial cells, and endothelial cells.

Targets: T cells, fibroblasts, epithelial and endothelial cells.

Function: Role in metabolic, physiological, haematopoietic activities, regulation of the immune responses & TNF-α path.

IL-1b

Type of interleukin activated by: macrophages, monocytes & DCs.

Target: T cells, fibroblasts, epithelial and endothelial cells.

Function: Mediates inflammatory response and role in: proliferation, differentiation & apoptosis.

IL-1Ra

Type of interleukin receptor activated by: Monocytes, macrophages, fibroblasts, neutrophils, endothelial and epithelial cells, and keratinocytes.

Targets: T cells, fibroblasts, epithelial and endothelial cells.

Functions as IL-1a/b antagonist.

IL-2

Type of interleukin activated by: CD4⁺ and CD8⁺ activatedT cells, DCs, NK and NKT cells, mast cells, and ILCs.

Target: CD4⁺ and CD8⁺ T cells, NK and B cells, and ILCs

Functions: proliferation of effector T/B cells; development of T-reg cells; differentiation and proliferation of NK cells; growth factor for B cells and stimulus for antibody synthesis; proliferation and cytokine production in ILCs.

IL-4

Type of interleukin activated by: T_H2 cells, basophils, eosinophils, mast cells, NKT cells. Targets T/B cells

IL-6

Type of interleukin activated by: Endothelial cells, fibroblasts, monocytes/macrophages, T cells, B cells, granulocytes, smooth muscle cells, eosinophils, chondrocytes, osteoblasts, mast cells, glial cells, keratinocytes.

Target: Hepatocytes, leukocytes, T cells, B cells, hematopoietic cells

Functions:

• Induction of acute-phase proteins in hepatocytes

• Leukocyte trafficking and activation

• T-cell differentiation, activation, and survival

• B-cell differentiation and production of IgG, IgM, and IgA

• Hematopoiesis

• Osteoclastogenesis and bone resorption

• Recruitment of mesenchymal vascular cells

• Neoangiogenesis in vivo

• Synovial fibroblast proliferation and cartilage degradation

• Survival of cholinergic neurons

• Induction of adrenocorticotropic hormone synthesis

IL-10

Type of interleukin activated by: T cells, B cells, monocytes, macrophages, and DCs

Target: Macrophages, monocytes, T cells, B cells, NK cells, mast cells, DCs, and granulocytes

Function: Immunosuppressive effect through APCs or direct effects on T-cell subsets; suppression of IgE and induction of IgG by B cells in human subjects

IL-12

Type of interleukin activated by: Monocytes, macrophages, neutrophils, microglia, DCs, B cells.

Target: T^H1 cells, NK cells

Function: Development and maintenance of T_H1 cells; activation of NK cells; support of DC maturation; induction of cytotoxicity