The Immune System Structure & Overview

Flashcards created for review of key concepts in The Immune System Structure & Overview.

Innate immunity

A nonspecific, always-active defense system that responds quickly but does not target specific pathogens or provide long-term protection.

Adaptive immunity

A slower but specific defense system that targets particular pathogens and retains memory for faster responses upon re-exposure.

Components of the immune system

Includes bone marrow, thymus, spleen, lymph nodes, and lymphatic vessels.

B cells

Produce antibodies and drive humoral immunity.

T cells

Coordinate immune responses and can directly kill infected cells, driving cell-mediated immunity.

Leukocytes

White blood cells derived from hematopoietic cells.

Granulocytes

Leukocytes that contain granules in their cytoplasm.

Agranulocytes

Leukocytes that lack granules.

Neutrophils

Function to fight bacteria.

Eosinophils

Function to fight parasites and mediate allergic reactions.

Basophils

Release histamine in allergic reactions.

Lymphocytes

Target specific pathogens and create long-term immunity.

Monocytes

Differentiate into macrophages.

Macrophages

Digest pathogens and debris and present antigens.

Role of skin in immunity

Acts as a physical barrier and contains antibacterial enzymes and antimicrobial compounds.

Effects of damaged skin

Pathogens can enter the body.

Respiratory tract defense

Mucus and cilia trap pathogens and move them toward the oropharynx for removal.

Lysozyme

Enzyme in the respiratory tract that breaks down bacterial cell walls.

Gastrointestinal tract protection

Stomach acid kills pathogens and gut bacteria compete with harmful microbes.

Antibiotic effects on GI defenses

Disrupt normal gut flora, allowing resistant strains to grow.

Complement system

Blood proteins that puncture pathogen membranes.

Complement activation pathways

Classical (antibody-dependent) and alternative (antibody-independent).

Interferons

Proteins released by virus-infected cells that prevent viral replication and dispersion.

Antigen-presenting cells (APCs)

Cells that engulf pathogens and present antigen fragments on MHC molecules.

Purpose of antigen presentation

Allows T cells to inspect antigens and determine an immune response.

MHC Class I

Presents intracellular antigens.

MHC Class II

Presents extracellular antigens.

Cells using MHC Class I

All nucleated cells.

CD8 cytotoxic T cells

Recognize and kill cells with abnormal antigen on MHC I.

Professional APCs

Macrophages, dendritic cells, some B cells, and activated epithelial cells.

Humoral immunity

Driven by B cells and antibodies.

Antibodies

Also called immunoglobulins (Ig).

Opsonization

Marking pathogens for phagocytosis.

Neutralization

Blocking pathogen activity.

Agglutination

Clumping pathogens for easier clearance.

Activation of complement

Via the constant region of antibodies.

Antibody structure

Y-shaped with two heavy chains and two light chains held together by disulfide bonds.

Variable region of antibody

Binds specific antigens.

Constant region of antibody

Binds immune cells and activates complement.

Isotype switching

B cells changing antibody class based on cytokine signals.

Antibody isotypes

IgM, IgD, IgG, IgE, IgA.

Cytotoxic immunity

Mediated by T cells.

Targets of CD8 T cells

Virus-infected cells, intracellular bacteria, and cancer cells.

Perforin

Molecule released by cytotoxic T cells to kill cells.

Granzyme

Molecule released that triggers apoptosis after pore formation.

CD4 helper T cells

Coordinate immune responses by releasing cytokines.

Regulatory T cells

Suppress immune responses to prevent autoimmunity.

Memory T cells

Provide rapid and strong responses upon re-exposure to the same antigen.

Innate and adaptive immunity in bacterial infections

Antibody-mediated responses target extracellular bacteria.

Innate and adaptive immunity in viral infections

Cytotoxic T cells target intracellular pathogens via MHC I.

Failure to recognize self-antigens

Can lead to autoimmune disease.

Functions of the lymphatic system

Equalize fluid distribution, transport fats in chylomicrons, and provide sites for immune responses.

Natural killer (NK) cells

Kill virus-infected cells without antigen specificity.

NK cell recognition

Detect cells with reduced or absent MHC I expression.

Circulating immune cells in blood

Neutrophils, macrophages, eosinophils, basophils, NK cells.

Phagocytic innate immune cells

Neutrophils and macrophages.

Cytokine-releasing innate immune cells

Macrophages.

Antigen presentation by macrophages

Engulf pathogen, break it into antigens, and present on MHC molecules.

Macrophages as a bridge

Initiate adaptive immunity through antigen presentation.

Dendritic cells' role

Primarily serve antigen presentation and activation of adaptive immunity.

Intracellular antigen degradation location

Proteasome.

Peptide entry to ER in MHC I pathway

Via TAP transporters.

Extracellular antigen degradation location

Endosomes.

Invariant chain function

Prevents premature peptide binding in MHC II.

Invariant chain before peptide loading

It is degraded.

Activated B cells differentiation

Into plasma cells and memory B cells.

Primary function of plasma cells

Secrete antibodies.

Advantage of memory B cells

Faster and stronger secondary immune responses.

Primary immune response characteristic

Slow, as B cells must activate and proliferate.

Secondary immune response characteristic

Faster and stronger due to memory cells.

Vaccine effectiveness principle

Formation of immune memory during primary exposure.

Pore-creating molecules in cytotoxicity

Perforin.

Apoptosis-triggering molecules

Granzymes.

MHC Class I activation requirement

CD8 T-cell activation requires MHC Class I.

Main role of CD4 helper T cells

Coordinate immune responses via cytokine release.

Problem without regulatory T cells

Overactivation and autoimmunity.

Extracellular bacteria targeting

Primarily by antibodies and macrophage-mediated responses.

Intracellular viruses targeting

Primarily by cytotoxic T-cell responses.

Engulfing bacteria and presenting antigens

By macrophages and dendritic cells.

Killing virus-infected cells presenting MHC I

By CD8 cytotoxic T cells.

Self-antigen recognition prevention

Prevents immune attack against the body’s own cells.

Consequence of immune failure to recognize self

Autoimmune disease.

Overreaction to harmless substances

Leads to allergic (hypersensitivity) reactions.

Immunization definition

Gaining protection against a pathogen.

Types of immunity in immunization

Active immunity and passive immunity.

Lymphatic system vessel type

One-way vessels.

Structures along lymphatic vessels

Lymph nodes.

Lymphatic system connection to the cardiovascular system

Thoracic duct in the posterior chest.

Lymphatic system role in fluid balance

Equalizes fluid distribution.

Transportation of fats in the lymphatic system

Via chylomicrons.

Importance of lymph nodes

Sites for mounting immune responses.

Systems linked by the lymphatic system

Immune system and cardiovascular system.

Innate immune division response

Responds immediately without specificity.

Adaptive immune division characteristics

Provides specificity and memory.

Bridging immune cells

Antigen-presenting cells (macrophages, dendritic cells).

Pathogen type implied by MHC I presentation

Intracellular (e.g., viral).

Pathogen type for MHC II usage

Extracellular.

Cells expressing MHC I

All nucleated cells.

Cells expressing MHC II

Professional antigen-presenting cells.

T cell recognizing MHC I

CD8 cytotoxic T cells.