Specific Acquired Immunity Flashcards
Antigen
Any substance or foreign particles that stimulate ur immune system to produce antibodies against it
immunogen
Triggers specific immune response
Epitope or antigenic determinant
Part of antigen recognized by antibody
Tolerogen
Antigen that induces immunologic tolerance
Allergen
Antigen that induces anaphylaxis
Tumor antigens
- antigens presented by MHC I molecules on surface of tumor cells
TSAs
- tumor specific antigens
- presented only by tumor cells & not normal ones
- result from tumor specific mutation
Autoantigens
- normal protein or complex of proteins recognized by immune system of patients suffering from autoimmune disease
- under normal conditions, should not trigger immune response, but do due to loss of tolerance
Not all antigens are _____ while all immunogens are ____
- immunogens; antigens
Complete antigens
- proteins
- large
- capable of stimulating immune response
Hapten antigen
- incomplete
- reacts w/ specific antibody, not immunogenic by itself
- made immunogenic by conjugation to carrier
- penicillin
Endogenous antigen examples
- autoantigens
- tumor antigens
2 good immunogens
- protein antigens
- polysaccharide antigens
Weak to bad immunogens
- lipid antigens
- nucleic acid antigens
T or F: Some glycolipids and phospholipids can stimulate T cells and produce CMI
True
T or F: Nucleic acid antigens can become immunogenic when single stranded or complexed w/ proteins
True
T-dependent antigens
- don’t directly stimulate antibody prod. w/o T cells
- example: microbial proteins
T-independent antigens
- directly stimulate B cells to prod antibodies w/o T cells
- prod. almost only IgM
- no secondary response
- example: pneumococcal polysaccharide
Superantigens
- cause excessive activation of immune system
- non specific activation of t cells causing polyclonal T cell activation and massive cytokine release
- produced by pathogens as a defense mechanism agains immune system
- example: staph and strep
Conventional antigen
- stimulate production of monoclonal/oligoclonal t cell response
Properties of immunogens that influence immunogenicity
- foreigness: discrimiation between self and non self
- molecular size: bigger=stronger, smaller=weaker or non-immunogenic
- chemical composition: more complex= more immunogenic
- physical form: particulate antigens more immunogenic than soluble; denatured antigens more potent than native
- susceptibility to antigen processing and presentation: easily phagocytosed=more immunogenic
Biological system on host (influence on immunogenicity)
- genetic factors: patient lack/have altered genes code for receptors for antigens on B and T cells; may not have appropriate genes for APC to present antigen to helper t cells
- age
Method of administration (factors that affect immunogenicity)
- dose: above or below= not optimal
- route: SQ and IM= more potent compared to IV and IG
- adjuvants
Humoral immunity
Prod. of antibodies when antigens present and mediated by B lymphocytes
CMI
Prod. of cytotoxic T cells, activated macrophages, activated NK cells, and ctyokines in response to antigen
Mediated by t-lymphocytes
Adjuvant
- example: Aluminum-potassium sulfate
Jules freund (1930)
- freund’s incomplete adjuvant
- freund’s complete adjuvant
Freund’s complete adjuvant
- emulsion of h2O and mineral oil containing heat-killed mycobacteria
- stimulates production of TH1 cells
- administered @ early stage of immunization program
- rapid and immediate response
- can lead to development of disease in immunocompromised patients
Freud’s incomplete adjuvant
- emulsion of H2O and mineral oil w/o added mycobacteria
- stimulates production of Th2 cells
- administered @ later stage of immunization (usually for boosters after initial injection w/ complete adjuvant)
- slow response
- hard to formulate with antigen during vaccine prep.
Heat labule enterotoxin B (LTB)
- intramolecular adjuvant
- E. Coli version is strong mucosal adjuvant and immunogen; can be used as subunit vaccine candidate against ETEC-induced diarrhea
CD4
- glycoprotein co receptor for T cells
- found on APCs and helper t cells
CD8
- transmembrane glycoprotein
- co-receptor for TCR
- role in cell signaling, aiding w/ cytotoxic T cell-antigen interactions
CD3
- protein complex
- activated CD8+ and CD4+
Alpha/beta T cells-> CD4+ T cells ->…….
Th1, Th2, Th17, Treg
Th1
- produces: IFN-g, IL-2, TNF-b
- act on CD8+, T cell, NKs, Monocytes, B cells (Ig3)
- enhances cell-mediated cytotoxicity
Th2
- Produces IL-4, IL-5, IL-13
- act on eosinophils, B cells (IgE, Ig4)
- respond to worms and allergens
Th17
- act on neutrophils and eosinophils
- proinflammatory; response to extracellular bacteria and fungi
Treg
- produces TGF-b, IL-10
- acts on other lymphocytes
- inhibits function of T & B cells, dendritic cells, etc
Exogenous antigens assc w/ CD___ and class ___
CD4+; Class II
Endogenous antigens assc w/ CD___ and Class __
CD8; Class I
High IgM can mean
Potential current primary infection
Antibody functions during infection
- neutralization/ microbial binding
- cytotoxicity against virus infected cells
- opsonization
- complement fixation
- mast cell degranulation
IgG
- Major Ig in serum and formed in secondary responses
- escapes into extravascular spaces easily
- opsonize, agglutinate, and precipitate antigen
- increased amt in sera after initial lag after first immunization
- different in secondary responses
IgM
- 1st antibody formed in newborn vertebrates
- 1st/major Ig in primary immune response
- abt 900,000 daltons
- pentamer w/ j protein
- second highest in serum conc.
- intravascular, efficient in complement activation, etc.
IgA
- dimer w/ j protein
- minor serum component
- major Ig in external secretions in non-ruminants (IgG1 in ruminants)
- protects mucosal surfaces, mammary glands, eyes
- doesn’t activate complement system & isn’t opsonin
sIgA (secretory IgA)
- IgA secreted by plasma cell in mucosa & binds to receptor on epithelial cells
- protects IgA from proteolytic enzymes and facilitates sIgA into secretions
- in intravascular and secretions
IgD
- on membrane of B lymphocytes
- sensitive to proteolytic enzymes
- precise function unknown
- low concentration in serum
- role in antigen-triggered clonal prolif.
IgE
- Type I hypersensitivity
- binds mast cells and basophils & with antigen release vasoactive amines (histamine, serotonin)
- anti-parasitic immunity
- nasal secretions and saliva
- increased conc. In atopic skin diseases
IgY
Avian egg yolk
