Chapter 6 Flashcards
Body’s 3rd line of defense
Adaptive Immunity
Key players of Adaptive Immunity
- B Cells
- T Cells
Lymphoid Cells
- B Lymphocytes
- T Lymphocytes
- NK Cells
Lymphocytes Appearance
Lymphocytes appear very similar, but different sets carry different cluster of differentiation (CD) molecules on their surface
Immunoglobulins (Ig)
- Synthesized by B cells
- Synthesized & Secreted by Plasma Cells
- Antibodies
Antibody
- Ig with specficity for epitope on antigen
- Non-covalently bind antigens to immoblixe them or tag them for destruction
- Important in HUMORAL immunity
Effector Cells
Carry out specific functions to combat pathogen
Memory Cells
Persist in host, & upon re-challenge with same antigen, mediate immune response quicker & stronger than initial encounter
B Lymphocytes (B Cells) [Types]
- Plasma Cells
- Memory B Cells
Plasma Cells
- Produce antibody in a form that can be secreted & have little or no membrane-bound antibody
- Short-lived
- Effector Cells
Memory B Cells
- Express membrane-bound antibody as parent B Cell
- Long Lived
Basic Structure of Antibodies
- 2 Identical Heavy (H) Chains
- 2 Identical Light (L) Chains
- A Variable (V) Region
- A Constant (C) Region
Variable (V) Region
Antigen-Binding sites
Constant (C) Region
Limited variation in amino acid sequence
Enzymes that cleave Antibodies
- Papain - Fc
- Pepsin - F(ab)2
5 Immunoglobulin Isotypes
- IgA
- IgD
- IgE
- IgG
- IgM
IgG
- Most Abundant Class in Serum
- 2 gamma heavy chains & 2 kappa OR 2 lambda light chains
- Most abundant in secondary response
- IgG3 is most effective complement activator
- IgG4 is NOT able to activate complement
IgM
- Serum Ig
- Monomeric is membrane-bound on B cells
- Secreted as a Pentamer
- First Ig produced in primary response
- Complement Activator
IgA
- Serum Ig
- Predominant Ig in external secretions
- Exists primarily as monomer, but polymer can form (Dimer)
IgE
- Allergies
- Highly specialized toward recruiting effector functions of mast cells in epithelium, activated eosinophils present at mucosal surfaces, & basophils in blood
- Mediate Hypersensitivity reactions
IgD
- Together with IgM, is the major membrane-bound Ig expressed by mature B cells
Classical Pathway of Complement Activation
- Antigen-Antibody interaction
- begins with activation of C1
- Membrane attack complex
- C3b - increase opsonization
- Produce C3a, C5a, C4a
Opsonization
C3b receptors on surface of many phagocytes
Chemotaxis
- C5a & C5, C6, C7 complex attract neutrophils
- C5a also enhance neutrophil adhesion
Anaphylatoxin
C3a, C4a, & C5a cause degranulation of mast cells with release of mediators
Cytolysis
- Insertion of C5b, 6, 7, 8, 9 complex into cell membrane leads to lysis of many cells
- MAC
Enhancement of Antibody Production
Binding of C3b to its receptors on surface of activated B cells
Major Histocompatibility Molecules (MHC)
- Also called Human Leukocyte Antigen (HLA) Complex
- Self-Proteins
- cell membrane proteins
- Leads to transplant rejection
MHC I
- Expressed by nearly all nucleated cells of vertebrate species
- Associates with beta2 microglobulin (beta2m)
- Associates with CD8 / cytotoxic T cells
- Presents antigens from intracellular pathogens
MHC II
- Expressed only by Antigen-Presenting Cells (APCs)
- Dendritic Cells
- Macrophages
- B Cells
- Associates with CD4 / T helper cells
- Presents antigens from extracellular pathogens
T Cell Receptors (TCRs)
- alpha-beta OR gamma-delta polypeptide pair
- alpha-beta TCR characterized by high degree of specificity
- TCR is associated with CD3
- Cannot bind soluble epitopes, only fragments
TCR vs. BCR
- TCR is always membrane-bound
- Antigen-binding interaction of TCRs is weaker than that of antibodies
- Most TCRs are specific to anitgen combined with MHC, not to antigen itself
- TCR can’t bind soluble epitopes, ony fragments.
Cytokines
Low molecular weight soluble protein messengers
- Endocrine Action
- Paracrine Action
- Autocrine Action
Chemokines
Chemoattractant cytokines
Endocrine Action
Released into the bloodstream to effect distant cells
Paracrine Action
Released to effect nearby cells
Autocrine Action
Released, but then bind to receptors on the cell that produced them.
Innate Immunity System Cytokines
- IL-1
- TNF-alpha
- CXCL8
Adaptive Immunity Cytokines
- IL-2
- IL-4 (Big in inflammation)
- IL-17
Adhesion Molecules
Provide stable cell-to-cell contact
- Integrins
- Selectins
- Addressins
Integrins
Strengthen contact between WBCs & many cell types (vascular epithelium)
Selectins & Addressins
Limited in tissue distribution
Cluster of Differentiation (CD) Molecules
- CD3
- CD4
- CD8
CD3
Support TCR & initiate signal transduction
CD4
- Recognize non-peptide binding portion of MHC II
- T helper cells
CD8
- Recognize non-peptide binding portion of MHC I
- Cytotoxic T Cell
Tyrosine Phosphorylation
- An early step in many signaling pathways
- CD3 (T Cells) & Igalpha/beta (B Cells) are phosphorylated on Immunoreceptor Tyrosine Activation Motifs (ITAMs)
Signal Transduction Molecules
- JAK-STAT Pathway
- Ras-MAP Kinase Pathway
